The necessary steps to make a counter bore
• Clamp work piece
• Make hole of appropriate size
• Fix on chuck right type of counter bore
• Counter bore to the required depth
Drill press
A drill press.A drill press (also known as pedestal drill, pillar drill, or bench drill) is a fixed style of drill that may be mounted on a stand or bolted to the floor or workbench. A drill press consists of a base, column (or pillar), table, spindle (or quill), and drill head, usually driven by an induction motor. The head has a set of handles (usually 3) radiating from a central hub that, when turned, move the spindle and chuck vertically, parallel to the axis of the column. The table can be adjusted vertically and is generally moved by a rack and pinion; however, some older models rely on the operator to lift and reclamp the table in position. The table may also be offset from the spindle's axis and in some cases rotated to a position perpendicular to the column. The size of a drill press is typically measured in terms of swing. Swing is defined as twice the throat distance, which is the distance from the center of the spindle to the closest edge of the pillar. For example, a 16-inch (410 mm) drill press will have an 8-inch (200 mm) throat distance.
A drill press has a number of advantages over a hand-held drill:
less effort is required to apply the drill to the workpiece. The movement of the chuck and spindle is by a lever working on a rack and pinion, which gives the operator considerable mechanical advantage.
the table allows a vise or clamp to position and lock the work in place making the operation much more secure.
the angle of the spindle is fixed in relation to the table, allowing holes to be drilled accurately and repetitively.
DrillSpeed change is achieved by manually moving a belt across a stepped pulley arrangement. Some drill presses add a third stepped pulley to increase the speed range. Modern drill presses can, however, use a variable-speed motor in conjunction with the stepped-pulley system; a few older drill presses, on the other hand, have a sort of traction-based continuously variable transmission for wide ranges of chuck speeds instead, which can be changed while the machine is running.
Drill presses are often used for miscellaneous workshop tasks such as sanding, honing or polishing, by mounting sanding drums, honing wheels and various other rotating accessories in the chuck. This can be dangerous on many presses, where the chuck arbor is held in the spindle purely by the friction of a Morse taper instead of being held securely by a drawbar.
[edit] Geared head drill
The geared head drill is identical to the drill press in most respects, however they are generally of sturdier construction and often have power feed installed on the quill mechanism, and safety interlocks to disengage the feed on overtravel. The most important difference is the drive mechanism between motor and quill is through a gear train (there are no vee belts to tension). This makes these drills suitable for use with larger drill bits.
[edit] Radial arm drill
A radial arm drill is a geared head drill that can be moved away from its column along an arm that is radial from the column. These drills are used for larger work where a geared head drill would be limited by its reach, the arm can swivel around the column so that any point on the surface of the table can be reached without moving the work piece. The size of work that these drills can handle is considerable as the arm can swivel out of the table's area, allowing an overhead crane to place the workpiece on the fixed table. Vises may be used with these machines but the work is typically bolted to the table or a fixture.
[Mill drills are a lighter alternative to a milling machine. They combine a drill press (belt driven) with the X/Y coordinate abilities of the milling machine's table and a locking collet that ensures that the cutting tool will not fall from the spindle when lateral forces are experienced against the bit. Although they are light in construction, they have the advantages of being space-saving and versatile as well as inexpensive, being suitable for light machining that may otherwise not be affordable.
The seven variables that should be considered prior to selecting a cutting
speed for a twist drill
i) Type of work piece ,ii) Type of cutting tool ,iii)Rigidity of machine ,iv)
Rigidity of set up ,v) accuracy required ,vi) surface finish required ,vii) type of cutting fluid
2009年1月4日 星期日
ट्विस्ट Drill
a) The three major parts of a twist drill
• Flute provide rake angle , allow chip to escape ,allow oil to reach work piece.
• The land are narrow ridge along the flute that bears against the wall of hole to prevent sticking
• The lip is the cutting edge.
b Grinding too much clearance on the cutting lips of a twist drill will reduce the strength of twist drill and so the drill bit will easily break
2008年6月16日 星期一
7)Milling Machine Safety
1) Ensure that work piece is fixed tighnenly
2)Ensure that cutter is properly tighten
3)Do not made sjustment and measurement when machine is operating
4)Do not remove chip by hands
5)Plan before carry out a job.
2)Ensure that cutter is properly tighten
3)Do not made sjustment and measurement when machine is operating
4)Do not remove chip by hands
5)Plan before carry out a job.
6. Milling Machine Adjustments
6. Milling Machine Adjustments
a. Vertical Milling Machine.
(1) Adjustments.
(a) Proper gib adjustment procedures must be done after 40 hours on new mills.
(b) Each 700 and 800 series of mills have three gibs. One at the front dovetail of
the table, one on the left dovetail of the saddle, and one on the left dovetail of the
knee. Each gib is supplied with two lock or adjustment screws. The table gib has a
lock screw on the right front of the saddle and the adjusting screw on the left front
of the saddle.
(c) The saddle gib is at the rear of the saddle on the left side, while the adjusting
screw is at the front of the saddle on the left side. The knee gib lock screw is on
the bottom of the knee on the left side and the adjusting screw is on the top on the
left side.
(d) To adjust the table gib, loosen the table gib lock screw several turns and
tighten the adjusting screw on the opposite side of the table until the gib is
pressing against the table dovetail. Tighten the lock screw. (Do not tighten the lock
screw too tight as it distorts the gib.) Run the table back and forth and check the
table for drag. To adjust the saddle and knee, use the same procedures as above.
(2) Adjustments With The Dial Indicator.
(a) When checking the gibs with a dial indicator, the following checks should be
made: (Use figure 22 as reference.)
(b) With the dial indicator mounted, as in Position 3, the table can be tested for
looseness by pulling back and forth on the end of the table. Anything over
0.0015-inch is too much and requires the gibs to be adjusted, also the table
should snap back to the "0" reading each time after the table is released.
(c) To check the saddle gib, the indicator should be mounted as in Position 7 and
the same tolerance should exist here.
(d) The knee gib will be checked as shown, with the dial indicator in Position 5,
by grasping the table and lifting up and pushing down. The reading of deflection
here should not be more than 0.0003 of an inch.
(e) As a final check, set the dial indicator on Position 2 and run the table to its
extreme right and left positions. The indicator runout should not be more than
0.0015 of an inch.
(3) Quill Feed Clutch. Adjustment of this clutch is as follows:
a. Vertical Milling Machine.
(1) Adjustments.
(a) Proper gib adjustment procedures must be done after 40 hours on new mills.
(b) Each 700 and 800 series of mills have three gibs. One at the front dovetail of
the table, one on the left dovetail of the saddle, and one on the left dovetail of the
knee. Each gib is supplied with two lock or adjustment screws. The table gib has a
lock screw on the right front of the saddle and the adjusting screw on the left front
of the saddle.
(c) The saddle gib is at the rear of the saddle on the left side, while the adjusting
screw is at the front of the saddle on the left side. The knee gib lock screw is on
the bottom of the knee on the left side and the adjusting screw is on the top on the
left side.
(d) To adjust the table gib, loosen the table gib lock screw several turns and
tighten the adjusting screw on the opposite side of the table until the gib is
pressing against the table dovetail. Tighten the lock screw. (Do not tighten the lock
screw too tight as it distorts the gib.) Run the table back and forth and check the
table for drag. To adjust the saddle and knee, use the same procedures as above.
(2) Adjustments With The Dial Indicator.
(a) When checking the gibs with a dial indicator, the following checks should be
made: (Use figure 22 as reference.)
(b) With the dial indicator mounted, as in Position 3, the table can be tested for
looseness by pulling back and forth on the end of the table. Anything over
0.0015-inch is too much and requires the gibs to be adjusted, also the table
should snap back to the "0" reading each time after the table is released.
(c) To check the saddle gib, the indicator should be mounted as in Position 7 and
the same tolerance should exist here.
(d) The knee gib will be checked as shown, with the dial indicator in Position 5,
by grasping the table and lifting up and pushing down. The reading of deflection
here should not be more than 0.0003 of an inch.
(e) As a final check, set the dial indicator on Position 2 and run the table to its
extreme right and left positions. The indicator runout should not be more than
0.0015 of an inch.
(3) Quill Feed Clutch. Adjustment of this clutch is as follows:
5) Basic Milling operations
General. The milling machine is one of the most versatile metalworking machines in a
shop. It is capable of performing simple operations, such as milling a flat surface or drilling a
hole, or more complex operations, such as milling helical gear teeth. It would be impractical to
attempt to discuss all of the operations that a milling machine can do. The success of any
milling operation depends to a great extent upon judgment in setting up the job, selecting the
proper cutter, and holding the cutter by the best means. Even though we will discuss only the
more common operations, the machinist will find that by using a combination of operations,
he will be able to produce a variety of work projects. Some fundamental practices have been
proved by experience to be necessary for good results on all jobs. Some of these practices
are mentioned below.
Plain Milling.
(1) General. Plain milling, also called surface milling and slab milling, is milling flat
surfaces with the milling cutter axis parallel to the surface being milled. Generally, plain
milling is accomplished with the workpiece surface mounted to the milling machine table
and the milling cutter mounted on a standard milling machine arbor. The arbor is well
supported in a horizontal plane between the milling machine spindle and one or more
arbor supports.
Angular Milling.
(1) General. Angular milling, or angle milling, is milling flat surfaces which are neither
parallel nor perpendicular to the axis of the milling cutter. A single-angle milling cutter
(figure 14) is used for this operation. Milling dovetails is a typical example of angular
milling. When milling dovetails, the usual angle of the cutter is 45°, 50°, 55°, or 60°,
based on common dovetail designs.
h. Face Milling.
(1) General. Face milling, also called end milling and side milling, is machining
surfaces perpendicular to the axis of the cutter.
Straddle Milling.
(1) General. When two or more parallel vertical surfaces are machined at a single cut,
the operation is called straddle milling. Straddle milling is accomplished by mounting
two side milling cutters on the same arbor, set apart so that they straddle the workpiece.
Gang Milling.
Gang milling is the term applied to an operation in which two or more milling cutters are used
together on one arbor when cutting horizontal surfaces. The usual method is to mount two or
more milling cutters of different diameters, shapes and/or widths on an arbor as shown in
figure 18. The possible cutter combinations are unlimited and are determined in each case by
the nature of the job.
Form Milling.
(1) General. Form milling is the process of machining special contours composed of
curves and straight lines, or entirely of curves, at a single cut. This is done with formed
milling cutters, shaped to the contour to be cut, or with a fly cutter ground for the job.
(2) Operation. The more common form milling operations involve milling half-round
recesses and beads and quarter-round radii on the workpieces (figure 19). This
operation is accomplished by using convex, concave, and corner rounding milling
cutters ground to the desired circle diameter.
(3) Other jobs for formed milling cutters include milling intricate patterns on workpieces
and milling several complex surfaces in a single cut, such as produced by gang milling.
l. Woodruff Keyway Milling.
(1) General. Keyways are machined grooves of different shapes, cut along the axis of
the cylindrical surface of shafts, into which keys are fitted to provide a positive method
of locating and driving members mounted on the shafts. A keyway is also machined on
the mounted member to receive the key. The type of key and corresponding keyway to
be used depends on the class of work for which it is intended. The most commonly used
type of key is the woodruff.
(2) Operation.
(a) Woodruff keys are semi-cylindrical in shape and are manufactured in various
diameters and widths. The circular side of the key is seated into a keyway which is
milled into a shaft with a woodruff keyslot milling cutter having the same diameter.
m. Gear Cutting.
(1) General. Gear teeth are cut on the milling machine using formed milling cutters
called involute gear cutters. These cutters are manufactured in many pitch sizes and
shapes for different numbers of teeth per gear (table 4 on the following page).
(2) Operation. If involute gear cutters are not available and the teeth must be restored
on gears that cannot be replaced, a lathe cutter bit can be ground to the shape of the
gear tooth spaces and mounted in a flycutter for the operation. The gear is milled in the
following manner:
Drilling.
(1) General. The milling machine may be used effectively for drilling, since the
accurate location of the hole may be secured by means of the feed screw graduations.
Spacing holes in a circular path, such as the holes in an indexing plate, may be
accomplished by indexing the workpiece with the indexing head that is positioned
vertically.
(2) Operation. Twist drills may be supported in drill chucks that are fastened in the
milling machine spindle or mounted directly in the milling machine collets or adapters.
The workpiece to be drilled is fastened to the milling machine table by means of clamps,
vises, or angle plates. Remember, proper speeds and feeds are important functions to
consider when performing drilling operations on the milling machine.
o. Boring. Various types of boring toolholders may be used for boring on the milling
machine. The boring tool can either be a straight shank, held in chucks and holders, or
tapered shanks to fit collets and adapters. The two attachments most commonly used for
boring are the flycutter arbor and the offset boring head. The single-edge cutting tool that is
used for boring on the milling machine is the same as a lathe cutter bit. Cutting speeds,
feeds, and depth of cut should be the same as those prescribed for lathe operations.
shop. It is capable of performing simple operations, such as milling a flat surface or drilling a
hole, or more complex operations, such as milling helical gear teeth. It would be impractical to
attempt to discuss all of the operations that a milling machine can do. The success of any
milling operation depends to a great extent upon judgment in setting up the job, selecting the
proper cutter, and holding the cutter by the best means. Even though we will discuss only the
more common operations, the machinist will find that by using a combination of operations,
he will be able to produce a variety of work projects. Some fundamental practices have been
proved by experience to be necessary for good results on all jobs. Some of these practices
are mentioned below.
Plain Milling.
(1) General. Plain milling, also called surface milling and slab milling, is milling flat
surfaces with the milling cutter axis parallel to the surface being milled. Generally, plain
milling is accomplished with the workpiece surface mounted to the milling machine table
and the milling cutter mounted on a standard milling machine arbor. The arbor is well
supported in a horizontal plane between the milling machine spindle and one or more
arbor supports.
Angular Milling.
(1) General. Angular milling, or angle milling, is milling flat surfaces which are neither
parallel nor perpendicular to the axis of the milling cutter. A single-angle milling cutter
(figure 14) is used for this operation. Milling dovetails is a typical example of angular
milling. When milling dovetails, the usual angle of the cutter is 45°, 50°, 55°, or 60°,
based on common dovetail designs.
h. Face Milling.
(1) General. Face milling, also called end milling and side milling, is machining
surfaces perpendicular to the axis of the cutter.
Straddle Milling.
(1) General. When two or more parallel vertical surfaces are machined at a single cut,
the operation is called straddle milling. Straddle milling is accomplished by mounting
two side milling cutters on the same arbor, set apart so that they straddle the workpiece.
Gang Milling.
Gang milling is the term applied to an operation in which two or more milling cutters are used
together on one arbor when cutting horizontal surfaces. The usual method is to mount two or
more milling cutters of different diameters, shapes and/or widths on an arbor as shown in
figure 18. The possible cutter combinations are unlimited and are determined in each case by
the nature of the job.
Form Milling.
(1) General. Form milling is the process of machining special contours composed of
curves and straight lines, or entirely of curves, at a single cut. This is done with formed
milling cutters, shaped to the contour to be cut, or with a fly cutter ground for the job.
(2) Operation. The more common form milling operations involve milling half-round
recesses and beads and quarter-round radii on the workpieces (figure 19). This
operation is accomplished by using convex, concave, and corner rounding milling
cutters ground to the desired circle diameter.
(3) Other jobs for formed milling cutters include milling intricate patterns on workpieces
and milling several complex surfaces in a single cut, such as produced by gang milling.
l. Woodruff Keyway Milling.
(1) General. Keyways are machined grooves of different shapes, cut along the axis of
the cylindrical surface of shafts, into which keys are fitted to provide a positive method
of locating and driving members mounted on the shafts. A keyway is also machined on
the mounted member to receive the key. The type of key and corresponding keyway to
be used depends on the class of work for which it is intended. The most commonly used
type of key is the woodruff.
(2) Operation.
(a) Woodruff keys are semi-cylindrical in shape and are manufactured in various
diameters and widths. The circular side of the key is seated into a keyway which is
milled into a shaft with a woodruff keyslot milling cutter having the same diameter.
m. Gear Cutting.
(1) General. Gear teeth are cut on the milling machine using formed milling cutters
called involute gear cutters. These cutters are manufactured in many pitch sizes and
shapes for different numbers of teeth per gear (table 4 on the following page).
(2) Operation. If involute gear cutters are not available and the teeth must be restored
on gears that cannot be replaced, a lathe cutter bit can be ground to the shape of the
gear tooth spaces and mounted in a flycutter for the operation. The gear is milled in the
following manner:
Drilling.
(1) General. The milling machine may be used effectively for drilling, since the
accurate location of the hole may be secured by means of the feed screw graduations.
Spacing holes in a circular path, such as the holes in an indexing plate, may be
accomplished by indexing the workpiece with the indexing head that is positioned
vertically.
(2) Operation. Twist drills may be supported in drill chucks that are fastened in the
milling machine spindle or mounted directly in the milling machine collets or adapters.
The workpiece to be drilled is fastened to the milling machine table by means of clamps,
vises, or angle plates. Remember, proper speeds and feeds are important functions to
consider when performing drilling operations on the milling machine.
o. Boring. Various types of boring toolholders may be used for boring on the milling
machine. The boring tool can either be a straight shank, held in chucks and holders, or
tapered shanks to fit collets and adapters. The two attachments most commonly used for
boring are the flycutter arbor and the offset boring head. The single-edge cutting tool that is
used for boring on the milling machine is the same as a lathe cutter bit. Cutting speeds,
feeds, and depth of cut should be the same as those prescribed for lathe operations.
4) Milling Cutters
Milling Cutters
a. General.
(1) There are different types of milling machine cutters. Some cutters can be used for
several operations, others can be used for only one operation. Some cutters have
straight teeth, others have helical teeth. Some cutters have mounting shanks, others
have mounting holes. The machine operator must decide which cutter to use. To make
this decision, he must be familiar with various types of cutters and their uses.
(2) Standard milling cutters are made in many shapes and sizes for milling both regular
and irregular shapes. Various cutters designed for specific purposes also are available.
(3) Milling cutters generally take their names from the operation which they perform.
Those commonly recognized are: (1) plain milling cutters of various widths and
diameters, used principally for milling flat surfaces which are parallel to the axis to the
cutter; (2) angular milling cutters, designed for milling V-grooves and the grooves in
reamers, taps, and milling cutters; (3) face milling cutters, used for milling flat surfaces
at right angles to the axis of the cutter; and (4) forming cutters, used for the production
of surfaces with some form of irregular outline.
(4) Milling cutters may also be classified as arbor-mounted, or shank-mounted.
Arbor-mounted cutters are mounted on the straight shanks of an arbor. The arbor is
then inserted into the milling machine spindle.
(5) Milling cutters may have straight, right-hand, left-hand, or staggered teeth. Straight
teeth are parallel to the axis of the cutter. If a helix angle twists in a clockwise direction,
the cutter has right-hand teeth. If the helix angle twists in a counterclockwise direction,
the cutter has left-hand teeth. The teeth on staggered-tooth cutters are alternately
left-hand and right-hand.
b. Milling Cutter Nomenclature. Figure 23 shows two views of a common milling cutter with
its parts and angles identified. These parts and angles are common to all types of cutters in
some form.
(1) Pitch. The pitch refers to the angular distance between like parts on the adjacent
teeth. The pitch is determined by the number of teeth.
(2) Face of Tooth. The tooth face is the forward facing surface of the tooth which forms
the cutting edge.
(3) Cutting Edge. The cutting edge is the angle on each tooth which performs the
cutting.
(4) Land. The land is the narrow surface behind the cutting edge of each tooth.
(5) Rake Angle. The rake angle is the angle formed between the face of the tooth and
the centerline of the cutter. The rake angle defines the cutting edge and provides a path
for chips that are cut from the workpiece.
(6) Primary Clearance Angle. The primary clearance angle is the angle of the land of
each tooth, measured from a line tangent to the centerline of the cutter at the cutting
edge. This angle prevents each tooth from rubbing against the workpiece after it makes
its cut.
(7) Secondary Clearance Angle. The secondary clearance angle defines the land of
each tooth and provides additional clearance for the passage of cutting oil and the
chips.
(8) Hole Diameter. The hole diameter determines the size of arbor that is necessary to
mount the milling cutter.
(9) Keyway. A keyway is present on all arbor-mounting cutters for locking the cutter to
the arbor.
(10) Spiral or Helix Angle.
(a) Plain milling cutters that are more than 3/4 inch in width are usually made
with spiral or helical teeth.
(b) A plain spiral-tooth milling cutter produces a better and smoother finish, and
requires less power to operate.
(c) A plain helix-tooth milling cutter is especially desirable where an uneven.surface or one with holes in it is to be milled.
(11) Types of Teeth. The teeth of milling cutters are either right-hand or left-hand,
viewed from the back of the machine. Right-hand milling cutters cut when rotated
clockwise; left-hand milling cutters cut when rotated counterclockwise.
(a) Saw Teeth. Saw teeth similar to those shown in figure 23 are either straight or
helical in the smaller sizes of plain milling cutters, metal slitting saw milling cutters,
and end milling cutters. The cutting edge is usually given about 5° primary
clearance angle. Sometimes the teeth are provided with offset nicks which break
up the chips and make coarser feeds poss Formed Teeth. Formed teeth are
usually specially made for machining irregular surfaces or profiles. The possible
varieties of formed-tooth milling cutters are almost unlimited. Convex, concave,
and corner-rounding milling cutters are of this type. Formed cutters are sharpened
by grinding the faces of the teeth radially. Repeated sharpenings are possible
without changing the contour of the cutting edge.
(c) Inserted Teeth. Inserted teeth are blades of high-speed steel inserted and
rigidly held in a blank of machine steel or cast iron. Different manufacturers use
different methods of holding the blades in place. Inserted teeth are more
economical and convenient for large-size cutters because of their reasonable
initial cost and because worn or broken blades can be replaced more easily and at
less cost.
(12) Kinds of Milling Cutters.
(a) Plain Milling Cutter (figure 24). The most common type of milling cutter is
known as a plain milling cutter. It is merely a metal cylinder having teeth cut on its
periphery for producing a flat horizontal surface (or a flat vertical surface in the
case of a vertical spindle machine). When the cutter is over 3/4 inch wide, the
teeth are usually helical, which gives the tool a shearing action which requires less
power, reduces chatter, and produces a smoother finish. Cutters with faces less
than 3/4 inch wide are sometimes made with staggered or alternate right-and
left-hand helical teeth. The shearing action, alternately right and left, eliminates
side thrust on the cutter and arbor. When a plain milling cutter is considerably
wider than its diameter, it is often called a slabbing cutter; slabbing cutters may
have nicked teeth that prevent formation of large chips.
(b) Metal Slitting Saw Milling Cutter (figure 25). The metal slitting saw milling
cutter is essentially a very thin, plain milling cutter. It is ground slightly thinner
toward the center to provide side clearance. It is used for metal sawing and for
cutting narrow slots in metal.
(c) Side Milling Cutters (figure 26). Side milling cutters are essentially plain
milling cutters with the addition of teeth on one or both sides.
1 A side milling cutter has teeth on both sides and on the periphery. When
teeth are added to one side only, the cutter is called a half-side milling cutter
and is identified as being either a right-hand or left-hand cutter. Side milling
cutters are generally used for slotting and straddle milling.
FIGURE 24. PLAIN MILLING CUTTERS.
FIGURE 25. SIDE AND METAL SLITTING SAW MILLING CUTTERS.
2 Interlocking tooth side milling cutters and staggered tooth side milling
cutters (figure 26) are used for cutting relatively wide slots with accuracy.
Interlocking tooth side milling cutters can be repeatedly sharpening without
changing the width of the slot that will be machined. After each sharpening,
a washer is placed between the two cutters to compensate for the ground-off
metal. The staggered tooth cutter is the most efficient type used for milling
slots where the depth exceeds the width.
FIGURE 26. SIDE MILLING CUTTERS.
(d) End Milling Cutters.
1 End milling cutters, also called end mills, have teeth on the end as well as
the periphery (figure 27). The smaller end milling cutters have shanks for
chuck mounting or direct spindle mounting. Larger end milling cutters (over 2
inches in diameter) are called shell end milling cutters and are mounted on
arbors like plain milling cutters. End milling cutters are employed in the
production of slots, keyways, recesses, and tangs. They are also used for
milling angles, shoulders, and the edges of workpieces.
FIGURE 27. END MILLING CUTTERS.
2 End milling cutters may have straight or spiral flutes. Spiral flute end
milling cutters are classified as left-hand or right-hand cutters, depending on
the direction of rotation of the flutes. If they are small cutters, they may have
either a straight or tapered shank.
3 Several common types of end milling cutters are illustrated in figure 27.
The most common end milling cutter is the spiral flute end milling cutter,
which contains four flutes. Two fluted end milling cutters are used for milling
slots and keyways where no drilled hole is provided for starting the cut.
These cutters drill their own starting holes. Straight flute end milling cutters
are generally used for milling soft or tough materials, while spiral flute cutters
are used mostly for cutting steel.
(e) Face Milling Cutter. Face milling cutters are cutters of large diameter having
no shanks. They are fastened directly to the milling machine spindle with
adapters. Face milling machine cutters are generally made with inserted teeth of
high-speed steel or tungsten carbide in a soft steel hub.
(f) T-Slot Milling Cutter (figure 28). The T-slot milling cutter is used to machine
T-slot grooves in worktables, fixtures, and other holding devices. The cutter has a
plain or side milling cutter mounted to the end of a narrow shank. The throat of the
T-slot is first milled with a side or end milling cutter and the headspace is then
milled with the T-slot milling cutter.
FIGURE 28. T-SLOT MILLING CUTTER.
(g) Woodruff Keyslot Milling Cutter. The woodruff keyslot milling cutter (figure 28)
is made in straight-shank, tapered-shank, and arbor-mounted types. The most
common cutters of this type, under 1 1/2 inches in diameter, are provided with a
shank. They have teeth on the periphery and slightly concave sides to provide
clearance. These cutters are used for milling semicylindrical keyways in shafts.
(h) Angle Milling Cutters. The angle milling cutter has peripheral teeth which are
neither parallel nor perpendicular to the cutter axis. Common operations
performed with angle cutters are cutting teeth in ratchet wheels, milling dovetails,
and cutting V-grooves. Angle cutters may be single-angle milling cutters (figure
29) or double-angle milling cutters. The single-angle cutter contains side-cutting
teeth on the flat side of the cutter. The angle of the right or left cutter edge is
usually 30°, 45°, or 60°. Double-angle cutters have included the angles of 45°, 60°,
and 90°.
FIGURE 29. SINGLE-ANGLE MILLING CUTTERS.
(i) Concave and Convex Milling Cutters. Concave and convex milling cutters
(figure 30) are formed tooth cutters shaped to produce concave and convex
contours of one-half circle or less. The size of the cutter is specified by the
diameter of the circular form the cutter produces.
(j) Corner-rounding Milling Cutter. The corner-rounding milling cutter (figure 30) is
a formed tooth cutter used for milling rounded corners on workpieces up to and
including one-quarter of a circle. The size of a cutter is specified by the radius of
the circular form the cutter produces, as with concave and convex cutters.
FIGURE 30. CONCAVE, CONVEX, AND CORNER ROUNDING MILLING CUTTERS.
(k) Gear Hob. The gear hob (figure 31) is a formed-tooth milling cutter with
helical teeth arranged like the thread on a screw. These teeth are fluted to
produce the required cutting edges. Hobs are generally used for such work as
finishing spur gears, spiral gears, and worm wheels. They may also be employed
for cutting ratchets and spline shafts.
FIGURE 31. GEAR HOB.
(1) Special Shaped-formed Filing Cutter. Formed milling cutters have the advantage of
being adaptable to any specific shape for special operations. The cutter is made for
each specific job. In the field, a fly cutter is made to machine a specific shape. The fly
cutter (figure 32) is often manufactured locally. It is a single-point cutting tool similar in
shape to a lathe or shaper tool. It is held and rotated by a fly cutter arbor. The cutter can
be ground to almost any shape, form, or contour that is desired. The cutter can be
sharpened many times without destroying the shape of the cutter or the cut being made.
There will be a very limited number of times when a special formed cutter will be
needed for cutting or boring operations, this is why a fly cutter is the most practical
cutter to use in this type of situation.
FIGURE 32. FLY CUTTER ARBOR AND FLY CUTTERS.
c. Selection of Milling Cutters. The following factors should be considered in the choice of
milling cutters:
(1) Type of Machine To Be Used. High-speed steel, stellite, and cemented carbide
cutters have the distinct advantage of being capable of rapid production when used on a
machine that can reach the proper speed.
(2) Method of Folding The Workpiece. For example, 45° angular cuts may either be
made with a 45° single-angle milling cutter while the workpiece is held in a swiveled
vise, or with an end milling cutter while the workpiece is set at the required angle in a
universal vise.
(3) Hardness of The Material To Be Cut. The harder the material, the greater will be
the heat that is generated during the cutting process. Cutters should be selected for
their heat-resisting properties.
(4) Amount of Material To Be Removed. A course-toothed milling cutter should be
used for roughing cuts, whereas a finer toothed milling cutter may be used for light cuts
and finishing operations.
(5) Number of Pieces To Be Cut. For example, when milling stock to length, the choice
of using a pair of side milling cutters to straddle the workpiece, a single-side milling
cutter, or an end milling cutter will depend upon the number of pieces to be cut.
(6) Class of Work Being Done. Some operations can be accomplished with more than
one type of cutter, such as in milling the square end on a shaft or reamer shank. In this
case, one or two side milling cutters or an end milling cutter may be used. However, for
the majority of operations, cutters are specially designed and named for the operation
they are to perform.
(7) Rigidity and Size of The Workpiece. The milling cutter used should be small
enough in diameter so that the pressure of the cut will not cause the workpiece to be
sprung or displaced while being milled.
(8) Size of The Milling Cutter. In selecting a milling cutter for a particular job, it should
be remembered that a small diameter cutter will pass over a surface in a shorter time
than a large diameter cutter fed at the same speed. This fact is illustrated in figure 33.
d. Care and Maintenance of Milling Cutters. The life of a milling cutter can be greatly
prolonged by intelligent use and proper storage. General rules for the care and maintenance
of milling cutters are given below:
(1) New cutters received from stock are usually wrapped in oilpaper which should not
be removed until the cutter is to be used.
(2) Care should be taken to operate the machine at the proper speed for the cutter that
is being used; excessive speed will cause the cutter to wear rapidly from overheating.
FIGURE 33. EFFECT OF MILLING CUTTER DIAMETER ON WORKPIECE TRAVEL.
(3) Whenever practicable, the proper cutting oil should be used on the cutter and the
workpiece during the operation, since lubrication helps prevent overheating and
consequent cutter wear.
(4) Cutters should be kept sharp, because dull cutters require more power to drive
them and this power, being transformed into heat, softens the cutting edges. Dull cutters
should be marked as such and set aside for grinding.
(5) A cutter should never be operated backward because, due to the clearance angle,
the cutter will rub, producing a great deal of frictional heat. Operating the cutter
backward may result in cutter breakage.
(6) Care should be taken to prevent the putter from striking the hard jaws of the vise,
chuck, clamping bolts, or nuts.
(7) A milling cutter should be thoroughly cleaned and lightly coated with oil before
storing.
(8) Cutters should be placed in drawers or bins in such a manner that their cutting
edges will not strike each other. Small cutters that have a hole in the center should be
hung on hooks or pegs, large cutters should be set on end. Tapered and straight shank
cutters may be placed in separate drawers, bins, or racks provided with suitable sized
holes to receive the shanks.
3. Conclusion
Milling cutters play an important role in performing milling machine operations. Knowing which
cutter to select and use for a specific operation, will at times, determine the overall quality of the
final product. The knowledge gained in this task on milling cutters will assist you in determining the
type of cutter(s) to employ for a specific operation, to include the nomenclature, selection, use and
care of milling cutters when tasked to perform milling machine operation
a. General.
(1) There are different types of milling machine cutters. Some cutters can be used for
several operations, others can be used for only one operation. Some cutters have
straight teeth, others have helical teeth. Some cutters have mounting shanks, others
have mounting holes. The machine operator must decide which cutter to use. To make
this decision, he must be familiar with various types of cutters and their uses.
(2) Standard milling cutters are made in many shapes and sizes for milling both regular
and irregular shapes. Various cutters designed for specific purposes also are available.
(3) Milling cutters generally take their names from the operation which they perform.
Those commonly recognized are: (1) plain milling cutters of various widths and
diameters, used principally for milling flat surfaces which are parallel to the axis to the
cutter; (2) angular milling cutters, designed for milling V-grooves and the grooves in
reamers, taps, and milling cutters; (3) face milling cutters, used for milling flat surfaces
at right angles to the axis of the cutter; and (4) forming cutters, used for the production
of surfaces with some form of irregular outline.
(4) Milling cutters may also be classified as arbor-mounted, or shank-mounted.
Arbor-mounted cutters are mounted on the straight shanks of an arbor. The arbor is
then inserted into the milling machine spindle.
(5) Milling cutters may have straight, right-hand, left-hand, or staggered teeth. Straight
teeth are parallel to the axis of the cutter. If a helix angle twists in a clockwise direction,
the cutter has right-hand teeth. If the helix angle twists in a counterclockwise direction,
the cutter has left-hand teeth. The teeth on staggered-tooth cutters are alternately
left-hand and right-hand.
b. Milling Cutter Nomenclature. Figure 23 shows two views of a common milling cutter with
its parts and angles identified. These parts and angles are common to all types of cutters in
some form.
(1) Pitch. The pitch refers to the angular distance between like parts on the adjacent
teeth. The pitch is determined by the number of teeth.
(2) Face of Tooth. The tooth face is the forward facing surface of the tooth which forms
the cutting edge.
(3) Cutting Edge. The cutting edge is the angle on each tooth which performs the
cutting.
(4) Land. The land is the narrow surface behind the cutting edge of each tooth.
(5) Rake Angle. The rake angle is the angle formed between the face of the tooth and
the centerline of the cutter. The rake angle defines the cutting edge and provides a path
for chips that are cut from the workpiece.
(6) Primary Clearance Angle. The primary clearance angle is the angle of the land of
each tooth, measured from a line tangent to the centerline of the cutter at the cutting
edge. This angle prevents each tooth from rubbing against the workpiece after it makes
its cut.
(7) Secondary Clearance Angle. The secondary clearance angle defines the land of
each tooth and provides additional clearance for the passage of cutting oil and the
chips.
(8) Hole Diameter. The hole diameter determines the size of arbor that is necessary to
mount the milling cutter.
(9) Keyway. A keyway is present on all arbor-mounting cutters for locking the cutter to
the arbor.
(10) Spiral or Helix Angle.
(a) Plain milling cutters that are more than 3/4 inch in width are usually made
with spiral or helical teeth.
(b) A plain spiral-tooth milling cutter produces a better and smoother finish, and
requires less power to operate.
(c) A plain helix-tooth milling cutter is especially desirable where an uneven.surface or one with holes in it is to be milled.
(11) Types of Teeth. The teeth of milling cutters are either right-hand or left-hand,
viewed from the back of the machine. Right-hand milling cutters cut when rotated
clockwise; left-hand milling cutters cut when rotated counterclockwise.
(a) Saw Teeth. Saw teeth similar to those shown in figure 23 are either straight or
helical in the smaller sizes of plain milling cutters, metal slitting saw milling cutters,
and end milling cutters. The cutting edge is usually given about 5° primary
clearance angle. Sometimes the teeth are provided with offset nicks which break
up the chips and make coarser feeds poss Formed Teeth. Formed teeth are
usually specially made for machining irregular surfaces or profiles. The possible
varieties of formed-tooth milling cutters are almost unlimited. Convex, concave,
and corner-rounding milling cutters are of this type. Formed cutters are sharpened
by grinding the faces of the teeth radially. Repeated sharpenings are possible
without changing the contour of the cutting edge.
(c) Inserted Teeth. Inserted teeth are blades of high-speed steel inserted and
rigidly held in a blank of machine steel or cast iron. Different manufacturers use
different methods of holding the blades in place. Inserted teeth are more
economical and convenient for large-size cutters because of their reasonable
initial cost and because worn or broken blades can be replaced more easily and at
less cost.
(12) Kinds of Milling Cutters.
(a) Plain Milling Cutter (figure 24). The most common type of milling cutter is
known as a plain milling cutter. It is merely a metal cylinder having teeth cut on its
periphery for producing a flat horizontal surface (or a flat vertical surface in the
case of a vertical spindle machine). When the cutter is over 3/4 inch wide, the
teeth are usually helical, which gives the tool a shearing action which requires less
power, reduces chatter, and produces a smoother finish. Cutters with faces less
than 3/4 inch wide are sometimes made with staggered or alternate right-and
left-hand helical teeth. The shearing action, alternately right and left, eliminates
side thrust on the cutter and arbor. When a plain milling cutter is considerably
wider than its diameter, it is often called a slabbing cutter; slabbing cutters may
have nicked teeth that prevent formation of large chips.
(b) Metal Slitting Saw Milling Cutter (figure 25). The metal slitting saw milling
cutter is essentially a very thin, plain milling cutter. It is ground slightly thinner
toward the center to provide side clearance. It is used for metal sawing and for
cutting narrow slots in metal.
(c) Side Milling Cutters (figure 26). Side milling cutters are essentially plain
milling cutters with the addition of teeth on one or both sides.
1 A side milling cutter has teeth on both sides and on the periphery. When
teeth are added to one side only, the cutter is called a half-side milling cutter
and is identified as being either a right-hand or left-hand cutter. Side milling
cutters are generally used for slotting and straddle milling.
FIGURE 24. PLAIN MILLING CUTTERS.
FIGURE 25. SIDE AND METAL SLITTING SAW MILLING CUTTERS.
2 Interlocking tooth side milling cutters and staggered tooth side milling
cutters (figure 26) are used for cutting relatively wide slots with accuracy.
Interlocking tooth side milling cutters can be repeatedly sharpening without
changing the width of the slot that will be machined. After each sharpening,
a washer is placed between the two cutters to compensate for the ground-off
metal. The staggered tooth cutter is the most efficient type used for milling
slots where the depth exceeds the width.
FIGURE 26. SIDE MILLING CUTTERS.
(d) End Milling Cutters.
1 End milling cutters, also called end mills, have teeth on the end as well as
the periphery (figure 27). The smaller end milling cutters have shanks for
chuck mounting or direct spindle mounting. Larger end milling cutters (over 2
inches in diameter) are called shell end milling cutters and are mounted on
arbors like plain milling cutters. End milling cutters are employed in the
production of slots, keyways, recesses, and tangs. They are also used for
milling angles, shoulders, and the edges of workpieces.
FIGURE 27. END MILLING CUTTERS.
2 End milling cutters may have straight or spiral flutes. Spiral flute end
milling cutters are classified as left-hand or right-hand cutters, depending on
the direction of rotation of the flutes. If they are small cutters, they may have
either a straight or tapered shank.
3 Several common types of end milling cutters are illustrated in figure 27.
The most common end milling cutter is the spiral flute end milling cutter,
which contains four flutes. Two fluted end milling cutters are used for milling
slots and keyways where no drilled hole is provided for starting the cut.
These cutters drill their own starting holes. Straight flute end milling cutters
are generally used for milling soft or tough materials, while spiral flute cutters
are used mostly for cutting steel.
(e) Face Milling Cutter. Face milling cutters are cutters of large diameter having
no shanks. They are fastened directly to the milling machine spindle with
adapters. Face milling machine cutters are generally made with inserted teeth of
high-speed steel or tungsten carbide in a soft steel hub.
(f) T-Slot Milling Cutter (figure 28). The T-slot milling cutter is used to machine
T-slot grooves in worktables, fixtures, and other holding devices. The cutter has a
plain or side milling cutter mounted to the end of a narrow shank. The throat of the
T-slot is first milled with a side or end milling cutter and the headspace is then
milled with the T-slot milling cutter.
FIGURE 28. T-SLOT MILLING CUTTER.
(g) Woodruff Keyslot Milling Cutter. The woodruff keyslot milling cutter (figure 28)
is made in straight-shank, tapered-shank, and arbor-mounted types. The most
common cutters of this type, under 1 1/2 inches in diameter, are provided with a
shank. They have teeth on the periphery and slightly concave sides to provide
clearance. These cutters are used for milling semicylindrical keyways in shafts.
(h) Angle Milling Cutters. The angle milling cutter has peripheral teeth which are
neither parallel nor perpendicular to the cutter axis. Common operations
performed with angle cutters are cutting teeth in ratchet wheels, milling dovetails,
and cutting V-grooves. Angle cutters may be single-angle milling cutters (figure
29) or double-angle milling cutters. The single-angle cutter contains side-cutting
teeth on the flat side of the cutter. The angle of the right or left cutter edge is
usually 30°, 45°, or 60°. Double-angle cutters have included the angles of 45°, 60°,
and 90°.
FIGURE 29. SINGLE-ANGLE MILLING CUTTERS.
(i) Concave and Convex Milling Cutters. Concave and convex milling cutters
(figure 30) are formed tooth cutters shaped to produce concave and convex
contours of one-half circle or less. The size of the cutter is specified by the
diameter of the circular form the cutter produces.
(j) Corner-rounding Milling Cutter. The corner-rounding milling cutter (figure 30) is
a formed tooth cutter used for milling rounded corners on workpieces up to and
including one-quarter of a circle. The size of a cutter is specified by the radius of
the circular form the cutter produces, as with concave and convex cutters.
FIGURE 30. CONCAVE, CONVEX, AND CORNER ROUNDING MILLING CUTTERS.
(k) Gear Hob. The gear hob (figure 31) is a formed-tooth milling cutter with
helical teeth arranged like the thread on a screw. These teeth are fluted to
produce the required cutting edges. Hobs are generally used for such work as
finishing spur gears, spiral gears, and worm wheels. They may also be employed
for cutting ratchets and spline shafts.
FIGURE 31. GEAR HOB.
(1) Special Shaped-formed Filing Cutter. Formed milling cutters have the advantage of
being adaptable to any specific shape for special operations. The cutter is made for
each specific job. In the field, a fly cutter is made to machine a specific shape. The fly
cutter (figure 32) is often manufactured locally. It is a single-point cutting tool similar in
shape to a lathe or shaper tool. It is held and rotated by a fly cutter arbor. The cutter can
be ground to almost any shape, form, or contour that is desired. The cutter can be
sharpened many times without destroying the shape of the cutter or the cut being made.
There will be a very limited number of times when a special formed cutter will be
needed for cutting or boring operations, this is why a fly cutter is the most practical
cutter to use in this type of situation.
FIGURE 32. FLY CUTTER ARBOR AND FLY CUTTERS.
c. Selection of Milling Cutters. The following factors should be considered in the choice of
milling cutters:
(1) Type of Machine To Be Used. High-speed steel, stellite, and cemented carbide
cutters have the distinct advantage of being capable of rapid production when used on a
machine that can reach the proper speed.
(2) Method of Folding The Workpiece. For example, 45° angular cuts may either be
made with a 45° single-angle milling cutter while the workpiece is held in a swiveled
vise, or with an end milling cutter while the workpiece is set at the required angle in a
universal vise.
(3) Hardness of The Material To Be Cut. The harder the material, the greater will be
the heat that is generated during the cutting process. Cutters should be selected for
their heat-resisting properties.
(4) Amount of Material To Be Removed. A course-toothed milling cutter should be
used for roughing cuts, whereas a finer toothed milling cutter may be used for light cuts
and finishing operations.
(5) Number of Pieces To Be Cut. For example, when milling stock to length, the choice
of using a pair of side milling cutters to straddle the workpiece, a single-side milling
cutter, or an end milling cutter will depend upon the number of pieces to be cut.
(6) Class of Work Being Done. Some operations can be accomplished with more than
one type of cutter, such as in milling the square end on a shaft or reamer shank. In this
case, one or two side milling cutters or an end milling cutter may be used. However, for
the majority of operations, cutters are specially designed and named for the operation
they are to perform.
(7) Rigidity and Size of The Workpiece. The milling cutter used should be small
enough in diameter so that the pressure of the cut will not cause the workpiece to be
sprung or displaced while being milled.
(8) Size of The Milling Cutter. In selecting a milling cutter for a particular job, it should
be remembered that a small diameter cutter will pass over a surface in a shorter time
than a large diameter cutter fed at the same speed. This fact is illustrated in figure 33.
d. Care and Maintenance of Milling Cutters. The life of a milling cutter can be greatly
prolonged by intelligent use and proper storage. General rules for the care and maintenance
of milling cutters are given below:
(1) New cutters received from stock are usually wrapped in oilpaper which should not
be removed until the cutter is to be used.
(2) Care should be taken to operate the machine at the proper speed for the cutter that
is being used; excessive speed will cause the cutter to wear rapidly from overheating.
FIGURE 33. EFFECT OF MILLING CUTTER DIAMETER ON WORKPIECE TRAVEL.
(3) Whenever practicable, the proper cutting oil should be used on the cutter and the
workpiece during the operation, since lubrication helps prevent overheating and
consequent cutter wear.
(4) Cutters should be kept sharp, because dull cutters require more power to drive
them and this power, being transformed into heat, softens the cutting edges. Dull cutters
should be marked as such and set aside for grinding.
(5) A cutter should never be operated backward because, due to the clearance angle,
the cutter will rub, producing a great deal of frictional heat. Operating the cutter
backward may result in cutter breakage.
(6) Care should be taken to prevent the putter from striking the hard jaws of the vise,
chuck, clamping bolts, or nuts.
(7) A milling cutter should be thoroughly cleaned and lightly coated with oil before
storing.
(8) Cutters should be placed in drawers or bins in such a manner that their cutting
edges will not strike each other. Small cutters that have a hole in the center should be
hung on hooks or pegs, large cutters should be set on end. Tapered and straight shank
cutters may be placed in separate drawers, bins, or racks provided with suitable sized
holes to receive the shanks.
3. Conclusion
Milling cutters play an important role in performing milling machine operations. Knowing which
cutter to select and use for a specific operation, will at times, determine the overall quality of the
final product. The knowledge gained in this task on milling cutters will assist you in determining the
type of cutter(s) to employ for a specific operation, to include the nomenclature, selection, use and
care of milling cutters when tasked to perform milling machine operation
3. Milling Machine Accessories And Attachments
3. Milling Machine Accessories And Attachments
a. Arbors. Milling machine cutters can be mounted on several types of holding device. The
machinist must know the devices, and the purpose of each to make the most suitable tooling
setup for the operation to be performed. Technically, an arbor is a shaft on which a cutter is
mounted. For convenience, since there are so few types of cutter holders that are not arbors,
we will refer to all types of cutter holding devices as arbors.
(1) Description.
(a) Milling machine arbors are made in various lengths and in standard diameters
of 7/8, 1, 1 1/4, and 1 1/2 inch. The shank is made to fit the tapered hole in the
spindle, the other end is threaded.
NOTE
The threaded end may have left-handed or right-handed threads
.
(b) Arbors are supplied with one of three tapers to fit the milling machine spindle
(figure 4), the milling machines Standard taper, the Brown and Sharpe taper, and
the Brown and Sharpe taper with tang.
(c) The milling machine Standard taper is used on most machines of recent
manufacture. It was originated and designed by the milling machine
manufacturers to make removal of the arbor from the spindle much easier than will
those of earlier design.
(d) The Brown and Sharpe taper is found mostly on older machines. Adapters or
collets are used to adapt these tapers to fit the machines whose spindles have
milling machine Standard tapers.
(e) The Brown and Sharpe taper with tang also is used on some of the older
machines. The tang engages a slot in the spindle to assist in driving the arbor.
(2) Standard Milling Machine Arbor (figure 4, and figure 5).
(a) The Standard milling machine arbor has a straight, cylindrical shape, with a
Standard milling taper on the driving end and a threaded portion on the opposite
end to receive the arbor nut. One or more milling cutters may be placed on the
straight cylindrical shaft of the arbor and held in position by means of sleeves and
an arbor nut. The Standard milling machine arbor is usually splined and has keys,
used to lock each cutter to the arbor shaft. Arbors are supplied in various lengths
and standard diameters.
(b) The end of the arbor opposite the taper is supported by the arbor supports of
the milling machine. One or more supports are used, depending on the length of
the arbor and the degree of rigidity required. The end may be supported by a lathe
center, bearing against the arbor nut (figure 4) or by a bearing surface of the arbor
fitting inside a bushing of the arbor support. Journal bearings are placed over the
arbor in place of sleeves where an intermediate arbor support is positioned.
FIGURE 4. STANDARD MILLING MACHINE ARBOR INSTALLED.
(c) The most common means of fastening the arbor in the milling machine
spindle is by use of a draw-in bolt (figure 4). The bolt threads into the taper shank
of the arbor to draw the taper into the spindle and hold it in place. Arbors secured
in this manner are removed by backing out the draw-in bolt and tapping the end of
the bolt to loosen the taper.
(3) Screw Arbor (figure 5). Screw arbors are used to hold small cutters that have
threaded holes. These arbors have a taper next to the threaded portion to provide
alignment and support for tools that require a nut to hold them against a tapered
surface. A right-hand threaded arbor must be used for right-hand cutters; a left-hand
threaded arbor is used to mount left-hand cutters.
(4) Slitting Saw Milling Cutter Arbor (figure 5). The slitting saw milling cutter arbor is a
short arbor having two flanges between which the milling cutter is secured by tightening
a clamping nut. This arbor is used to hold the metal slitting saw milling cutters that are
used for slotting, slitting, and sawing operations.
(5) End Milling Cutter Arbor. The end milling cutter arbor has a bore in the end in which
the straight shank end milling cutters fit. The end milling cutters are locked in place by
means of a setscrew.
(6) Shell End Milling Cutter Arbor (figure 5). Shell end milling arbors are used to hold
and drive shell end milling cutters. The shell end milling cutter is fitted over the short
boss on the arbor shaft and is held against the face of the arbor by a bolt, or a retaining
screw. The two lugs on the arbor fit slots in the cutter to prevent the cutter from rotating
on the arbor during the machining operation. A special wrench is used to tighten and
loosen a retaining screw/bolt in the end of the arbor.
(7) Fly Cutter Arbor (figure 5). The fly cutter arbor is used to support a single-edge
lathe, shaper, or planer cutter bit, for boring and gear cutting operations on the milling
machine. These cutters, which can be ground to any desired shape, are held in the
arbor by a locknut. Fly cutter arbor shanks may have a Standard milling machine
spindle taper, a Brown and Sharpe taper, or a Morse taper.
FIGURE 5. TYPES OF MILLING MACHINE ARBORS.
b. Collets and Spindles.
(1) Description. Milling cutters that contain their own straight or tapered shanks are
mounted to the milling machine spindle with collets or spindle adapters which adapt the
cutter shank to the spindle.
(2) Collets. Collets for milling machines serve to step up or increase the taper sizes so
that small-shank tools can be fitted into large spindle recesses. They are similar to
drilling machine sockets and sleeves except that their tapers are not alike. Spring collets
are used to hold and drive straight-shanked tools. The spring collet chuck consists of a
collet adapter, spring collets, and a cup nut. Spring collets are similar to lathe collets.
The cup forces the collet into the mating taper, causing the collet to close on the straight
shank of the tool. Collets are available in several fractional sizes.
(3) Spindle Adapters. Spindle adapters are used to adapt arbors and milling cutters to
the standard tapers used for milling machine spindles. With the proper spindle adapters,
any tapered or straight shank cutter or arbor can be fitted to any milling machine, if the
sizes and tapers are standard.
a. Arbors. Milling machine cutters can be mounted on several types of holding device. The
machinist must know the devices, and the purpose of each to make the most suitable tooling
setup for the operation to be performed. Technically, an arbor is a shaft on which a cutter is
mounted. For convenience, since there are so few types of cutter holders that are not arbors,
we will refer to all types of cutter holding devices as arbors.
(1) Description.
(a) Milling machine arbors are made in various lengths and in standard diameters
of 7/8, 1, 1 1/4, and 1 1/2 inch. The shank is made to fit the tapered hole in the
spindle, the other end is threaded.
NOTE
The threaded end may have left-handed or right-handed threads
.
(b) Arbors are supplied with one of three tapers to fit the milling machine spindle
(figure 4), the milling machines Standard taper, the Brown and Sharpe taper, and
the Brown and Sharpe taper with tang.
(c) The milling machine Standard taper is used on most machines of recent
manufacture. It was originated and designed by the milling machine
manufacturers to make removal of the arbor from the spindle much easier than will
those of earlier design.
(d) The Brown and Sharpe taper is found mostly on older machines. Adapters or
collets are used to adapt these tapers to fit the machines whose spindles have
milling machine Standard tapers.
(e) The Brown and Sharpe taper with tang also is used on some of the older
machines. The tang engages a slot in the spindle to assist in driving the arbor.
(2) Standard Milling Machine Arbor (figure 4, and figure 5).
(a) The Standard milling machine arbor has a straight, cylindrical shape, with a
Standard milling taper on the driving end and a threaded portion on the opposite
end to receive the arbor nut. One or more milling cutters may be placed on the
straight cylindrical shaft of the arbor and held in position by means of sleeves and
an arbor nut. The Standard milling machine arbor is usually splined and has keys,
used to lock each cutter to the arbor shaft. Arbors are supplied in various lengths
and standard diameters.
(b) The end of the arbor opposite the taper is supported by the arbor supports of
the milling machine. One or more supports are used, depending on the length of
the arbor and the degree of rigidity required. The end may be supported by a lathe
center, bearing against the arbor nut (figure 4) or by a bearing surface of the arbor
fitting inside a bushing of the arbor support. Journal bearings are placed over the
arbor in place of sleeves where an intermediate arbor support is positioned.
FIGURE 4. STANDARD MILLING MACHINE ARBOR INSTALLED.
(c) The most common means of fastening the arbor in the milling machine
spindle is by use of a draw-in bolt (figure 4). The bolt threads into the taper shank
of the arbor to draw the taper into the spindle and hold it in place. Arbors secured
in this manner are removed by backing out the draw-in bolt and tapping the end of
the bolt to loosen the taper.
(3) Screw Arbor (figure 5). Screw arbors are used to hold small cutters that have
threaded holes. These arbors have a taper next to the threaded portion to provide
alignment and support for tools that require a nut to hold them against a tapered
surface. A right-hand threaded arbor must be used for right-hand cutters; a left-hand
threaded arbor is used to mount left-hand cutters.
(4) Slitting Saw Milling Cutter Arbor (figure 5). The slitting saw milling cutter arbor is a
short arbor having two flanges between which the milling cutter is secured by tightening
a clamping nut. This arbor is used to hold the metal slitting saw milling cutters that are
used for slotting, slitting, and sawing operations.
(5) End Milling Cutter Arbor. The end milling cutter arbor has a bore in the end in which
the straight shank end milling cutters fit. The end milling cutters are locked in place by
means of a setscrew.
(6) Shell End Milling Cutter Arbor (figure 5). Shell end milling arbors are used to hold
and drive shell end milling cutters. The shell end milling cutter is fitted over the short
boss on the arbor shaft and is held against the face of the arbor by a bolt, or a retaining
screw. The two lugs on the arbor fit slots in the cutter to prevent the cutter from rotating
on the arbor during the machining operation. A special wrench is used to tighten and
loosen a retaining screw/bolt in the end of the arbor.
(7) Fly Cutter Arbor (figure 5). The fly cutter arbor is used to support a single-edge
lathe, shaper, or planer cutter bit, for boring and gear cutting operations on the milling
machine. These cutters, which can be ground to any desired shape, are held in the
arbor by a locknut. Fly cutter arbor shanks may have a Standard milling machine
spindle taper, a Brown and Sharpe taper, or a Morse taper.
FIGURE 5. TYPES OF MILLING MACHINE ARBORS.
b. Collets and Spindles.
(1) Description. Milling cutters that contain their own straight or tapered shanks are
mounted to the milling machine spindle with collets or spindle adapters which adapt the
cutter shank to the spindle.
(2) Collets. Collets for milling machines serve to step up or increase the taper sizes so
that small-shank tools can be fitted into large spindle recesses. They are similar to
drilling machine sockets and sleeves except that their tapers are not alike. Spring collets
are used to hold and drive straight-shanked tools. The spring collet chuck consists of a
collet adapter, spring collets, and a cup nut. Spring collets are similar to lathe collets.
The cup forces the collet into the mating taper, causing the collet to close on the straight
shank of the tool. Collets are available in several fractional sizes.
(3) Spindle Adapters. Spindle adapters are used to adapt arbors and milling cutters to
the standard tapers used for milling machine spindles. With the proper spindle adapters,
any tapered or straight shank cutter or arbor can be fitted to any milling machine, if the
sizes and tapers are standard.
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