Practical Treatise on Milling and Milling Machines/Chapter 5

by Brown & Sharpe Mfg. Co.

chapter v
Attachments

A milling machine is, in itself, a most versatile tool, but when equipped with a suitable set of attachments, the range of work that can be done is greatly increased. Also there are often milling operations that can be performed without an attachment, but by using one the jobs can be more easily and quickly done. Attachments are, therefore, most desirable auxiliaries where a machine is not confined to one manufacturing operation, but is used for general milling purposes. And even in manufacturing, where a machine is kept on one operation, an attachment can often be used to good advantage.

Broadly speaking, the variety of attachments for use on milling machines is almost limitless. To fully realize this, one has only to visit several shops producing different kinds of work on milling machiens, and observe the methods employed. Devices of every conceivable description will be seen in use in connection with the machines, and, while many of them may be of a more or less special character and adaptable only to a particular operation, they are, strictly speaking, attachments. Some of these devices, however, are so designed that quite a number of different operations can be performed by their use, or the same operation can be repeated on a variety of pieces. It is these mechanisms that we are accustomed to regard more especially as attachments, while those designed for single operations are almost universally known in shops as fixtures. It would be useless to attempt to treat of the latter, as their designs and purposes are as varied as the different lines of mechanical work.

The efficency of attachments, like machines, depends largely upon their design and construction, and a poorly designed or built mechanism of this type can seriously impair the quality of work and thus defeat its own object.

Many forms of attachments designed for the same purpose will be found, as it is necessary for every manufacturer to adapt attachments to his machine. This is a matter of minor importance, however, and a close examination will reveal that, as a general rule, the principles of the different mechanisms are similar. This chapter is devoted to

Fig. 18


Fig. 19


Fig. 20

our line of attachments, as typical of attachments in general, with brief descriptions of their general designs and functions. From this information it is hoped that the reader will be able to understand the necessity for, and advantages of, these mechanisms.

Vises. While vises are furnished as a part of the regular equipment of most milling machines, and for that reason are not styled as attachments, notwithstanding this, they may be so properly classed.

Vises are useful for holding a large variety of small work while it is being milled or planed. Numerous illustrations of their employment can be found in the examples of operations throughout Chapters VII and IX. It is essential that they be as rigid as possible, and to this end should be built with well-designed, strong, close-fitting parts. It is well to have them set low so as to bring the work close to the table.

There are several styles of vises. Fig. 18 shows a Plain Vise, for lighter operations. The bed and slide are of cast iron, while the jaws are tool steel, hardened and ground. It is fastened to the surfaces of the table by means of a screw that passes through the bed and threads into a nut inserted in a table T slot. The head of th eclamping screw fits a counterbore in the vise bed, and is flush with the top of the casting, so that it does not interfere with the movement of the sliding jaw.

The vise shown in Fig. 19 is known as a Flanged Vise, adn differs little from the Plain Vise except in the method of clamping to the table. A slotted flange is provided at each end for this purpose, and regular T slot bolts with nuts and washers are employed. Also a pair of straps are furnished for clamping the vise at the sides when this is necessary.

It is sometimes desired to mill angular or tapering work. A vise provided with a swivel, and known by that name, is shown in Fig. 20, and by its use this work can be readily done. The vise proper is of the same design as the plain vise, but the bottom of the bed fits into a split ring in a base. This ring is tapered on the inside to draw the bed to its seat, and holds it rigidly without disturbing the alignment. The split ring is closed by either one of the two clamping bolts at the side, two being provided for convenience in setting. The entire circumference of the base is graduated to degrees, and the vise can be readily swung to any angle to the table ways. The base is provided with flanges for fastening it to the surface of the table.

Fig. 21 shows a Tool Makers' Universal Vise, designed to meet the requirements of tool makers and machine shops where a great variety of work is encountered. It is found of advantage for holding irregular or angular pieces and forms, also in determining and forming the edges for model parts of machines and work of a similar class. Often this vise will take the palce of an expensive fixture. It can be set at any angle and the work placed in position or removed

Fig. 21

without disturbing the setting. It can also be easily removed form one machine to another and several operations performed without removing the piece of work. The base is double, and is fastened to the table by bolts that fit into the table T slots. It has two sets of bolt slots to allow for moving the vise back when set in a vertical plane. The upper part is a hinged knee, that swivels on the lower part of the base, and it can be set at any angle in a horizontal plane, graduations to degrees indicating the position. The top section of the knee is hinged to the lower part in such a manner that it can be set at any angle to 90° in a vertical plane, and clamped rigidly in position by the nut on the end of the bolt forming the hinge and by the bolt at the joint in the bracing levers. Graduations on a steel dial at the side of the vise indicate the elevation of the knee. A swiveling movement is also provided for the vise proper on the upper part of the hinged knee, and it can be set and clamped at any angle to the axis of the bolt forming the hinge.

Index Centres. These mechanisms are employed for obtaining exact spacing of more common numbers of divisions upon the periphery of pieces of work, such as in cutting the teeth of small gears, ratchets and cutters, fluting taps and reamers, milling the sides of nuts and heads of bolts, and various other purposes. They are used principally upon machines not fitted with a spiral head, for their functions in most instances can be equally well performed by the latter, which also offers many additional advantages.

Like otehr attachments, their efficiency is largely dependent upon their design, and it is important that they be exceedingly stiff, in order that the work may be rigidly supported. They should also be convenient to operate, so that indexing may be quickly accomplished.

One of the simplest forms of index centres, known as Single Dial Index Centres, is shown in Fig. 22. It consists of a head-stock and foot-stock of solid construction. The spindle of the head-stock is turned by means of the hand-wheel, and the divisions are indicated on the periphery of an index plate fastened to the spindle near the hand-wheel. There are holes in the back of the index plate corresponding to the divisions on its periphery, and a hardened steel taper pin is provided that is forced into the bushings of these holes by a

Fig. 22

spring, efficiently locking the spindle at any one of the divisions. The small lever near the top of the head-stock withdraws the taper pin when it is desired to index the work.

This style of index centres is found convenient whenever rapid indexing is to be done, as in cutting teeth in sprocket wheels and mills, or in milling grooves in taps, reamers and work of a similar kind. They are built in two sizes, one to accommodate work up to 8 inches diameter, and the other for work up to 12 inches diameter. The index plates or dials furnished have 24 divisions, or holes, but special plates having, for 8 inch centres, any number of holes up to 32, and, for 12 inch centres, any number up to 32, are sometimes made to order.

A common style of index centres, known as Plain Index Centres, is shown in Fig. 23. The spindle of the head-stock is revolved by means of a worm and wheel. The handle of the crank fastened to the worm shaft constitutes an index pin, and indexing is accomplished by means of a plate drilled with circles of different numbers of holes into which the spring pin of the crank fits. Thus it will be seen that the principle of indexing with these centres is the same as with the spiral head. For rapid indexing of the coarser divisions, the worm can be thrown out of mesh with the wheel and the spindle turned by hand; a circle

Fig. 23

of holes in the back of the worm wheel rim, and an index pin at the top of the head-stock provide for indexing when this is done.

These centres are built in sizes to accommodate work up to 10 inches and 12 inches diameter respectively. The nose of the spindle is threaded to receive a face plate or chuck. They are fitted with index sectors similar to those of the spiral head, and the index crank is adjustable so that it can be brought to the nearest hole without disturbing the setting. The index plates furnished divide all numbers to SO and all even numbers to 100, except 96.

Fig. 24 shows a pair of Universal Index Centres. The resemblance between them and the spiral head is marked; in fact, the foot-stock is identical with that furnished with the latter mechanism. All operations upon centres that do not require other than plain indexing and where there is no spiral to be cut, can be performed with these centres equally as well as with a spiral head.

These universal index centres are built in six sizes, to accommodate work up to 6, 10, 12, 12+¹⁄₂, 14 and 15 inches diameter. Divisions are indexed by means of the index crank and plates, the same

Fig. 24

as on the spiral head. The two smaller sizes are arranged for rapid

indexing of coarser divisions by disengaging the worm, and indexing with the plate fastened directly to the nose of the spindle, as on the spiral head. The index crank is adjustable and index sectors are employed. The index plates furnished with the 6 inch, 10 inch, 12 inch, 14 inch and 15 inch centres divide all numbers to 50, and all even numbers to 100, except 96; those furnished with the 12 1/2 inch centres divide all numbers to 100 and all even numbers to 134.

Index centres designed for manufacturing purposes where economy and rapidity of production are important factors, often have more than one spindle. Fig. 25 shows triple centres of this type. All three spindles of these centres are indexed simultaneously, and one thumbscrew firmly clamps them all, consequently three pieces of work can

Fig. 25

be finished in practically the same time it takes to machine one on single centres.

The spindles are rotated by a ratchet operated by the lever shown at the left of the head-stock. Indexing is accomplished by an index plate which divides all numbers as follows: 2, 3, 4, 5, 6, 7, 8, 10, 12, 14, 20 and 24. The index stop pin is shown at the left of the head-stock.

Using all three spindles, work up to 2 1/2 inches diameter can be taken; when only the two outside spindles are employed, work up to 5 inches diameter will swing.

Triple index centres of the design that has the index plate at the side of the head-stock similar to the spiral head are shown in Fig. 26. Centres of this same general design, but arranged for rapid indexing only, are also built.

The index plates furnished with these centres divide all numbers to 50, even numbers to 100, except 96. When rapid indexing is desired, the worm of the index crank is disengaged and the centres are turned by means of a pinion actuated by the crank at the left of the headstock; an index plate and stop pin provide for the divisions.

Fig. 26

The centres swing, using three spindles, 4 inches; using the two outside spindles, 8 inches.

Gear Cutting Attachment. The gear cutting attachment shown in Fig. 27 is useful for cutting spur gears of all diameters up to and including 16 inches, and is similar to ordinary index centres, only it

Fig. 27

will swing larger diameters. It is exceptionally rigid in construction and, to further insure steadiness to the gear while being cut, an adjustable rim rest is placed on the head-stock.

The worm and wheel of this attachment are accurately cut, and the wheel is of much larger diameter than that of ordinary index centres; consequently the possibility for error in spacing is materially lessened. The worm and worm wheel can be disengaged and the spindle turned by hand by. means of the handle at the back, when setting or testing work. The index plates furnished divide all numbers to 100, all even numbers to 134, and all numbers divisible by 4 to 200.

In addition to cutting gears, this attachment may be used on jig work where accurate indexing is an essential element. The spindle is threaded for the purpose of holding a chuck or face plate.

Vertical Spindle Milling Attachments. Vertical spindle milling attachments, including the Compound and Universal types, are used for a wide range of light and heavy milling, such as key seating, T slot cutting, spiral milling, face milling and work of a similar class; in fact, almost any operation that can be performed with a vertical
Fig. 28 spindle machine can be accomplished with a horizontal spindle machine when equipped with one of these attachments.

In die sinking, as well as all kinds of surface milling, the advantage of having the work flat on the table and in plain sight of the operator is readily appreciated. For metal patterns and similar work, these attachments are especially valuable, as a line or template can be followed very closely, thus reducing the hand finishing to a minimum.

It is very essential in designing attachments of this kind, that ample provision be made for solidly clamping the mechanism to the machine, and unless this can be done, their value is greatly restricted. The method of clamping shown in the accompanying illustrations is such that the attachment becomes practically an integral part of the machine. To be practical, the method of clamping must also be simple, for much of the value of an attachment lies in the convenience with which it can be put on and taken off the machine.

In all cases, the spindles of the attachments illustrated can be set to any angle from a vertical to a horizontal position, the angle being indicated by graduations reading to degrees.

Attachments of this kind are usually driven from the machine spindle through bevel gears, but Fig. 28 shows one that is driven by

Fig. 29

Fig. 30

means of a worm and wheel, and Fig. 30 illustrates one where spur

gears are employed in addition to bevel gears.

Vertical Spindle Milling Attachments as built by us are divided into two classes, light and heavy. With one exception, all of our machines can be fitted with both light and heavy styles.

Fig. 28 shows a light attachment for the smaller sizes of machines, and Fig. 29 a heavy style for the same machines. Fig. 29 is also representative of a light style for the larger sizes of machines, the heavy style for these machines being shown in Fig. 30. The spindle nose of these attachments, except that shown in Fig. 28, is

Fig. 31

tapered, hardened and ground; provided with taper hole, and has a recess in end to receive clutch on arbor or collets. The outer end of the heavy-style (Fig. 30) attachment is provided with a bearing that is stiffly supported by the arm braces.

Compound Vertical Spindle Milling Attachment. The Compound Vertical Spindle Milling Attachment, shown in Fig. 31 is particularly applicable to a large variety of milling, because it can be set in two planes. (See illustrations). It is especially advantageous when it is desired to set the spindle at an angle to the table, as in milling angular strips, table ways, etc., for with the spindle in this position, the full length of the table travel is available, and an ordinary end mill, instead of an angular cutter, can be used for milling the angle.
Fig. 32 Universal Milling Attachment. Fig. 32 shows the Universal Milling Attachment, and as its name implies, it is fully universal in regard to setting the spindle. In addition to the large amount of work already mentioned in connection with the Vertical and Compound Vertical Attachments, this mechanism can be used for many othe. operations, because of the fact that the spindle can be set at any angle in both horizontal or vertical planes. It is clamped to the face of the column and the outer end is inserted in the arbor Fig. 32 yoke to give additional stability.

Fig. 33 Horizontal Milling Attachment. We have mentioned the advantages to be derived from the use of vertical spindle milling attachments on horizontal spindle milling machines, and it is reasonable to suppose that to a certain extent, similar advantages are to be gained by the employment of a horizontal milling attachment on vertical spindle milling machines. An attachment of this kind is shown in Fig. 33. It is designed for use upon our No. 1 Vertical Spindle Machine, and with it such work as cutting spiral gears, racks, milling keyseats, etc., can be readily done. It is simple in construction and can be quickly attached to the machine.

Circular Milling Attachments. Circular Milling Attachments provide a means of economically doing such work as milling circles, segments of circles, circular slots, etc., on plain and irregular shaped pieces. With the addition of one of these attachments, a vertical spindle milling machine is fully equipped for all varieties of straight

Fig. 34

and circular milling within its capacity. Likewise, one of these attachments used in connection with a vertical spindle attachment offers similar advantages on a horizontal spindle machine. Fig. 34 shows an attachment that can be used on our univfe-sal, plain and vertical spindle milling machines. The table is rotatecf by means of a worm and wheel, and can be fed automatically in either direction by power derived from the table feed screw. It can also be operated by hand when desired. For quick setting, the worm is thrown out of mesh and the table turned to any position. The table remains locked in position when the feed is stopped, but when straight milling or drilling is to be done, an additional clamp,
Fig. 35 operated by a lever at the side of the attachment, is employed to further insure its stability. The table is heavy and has a wide bearing surface; its circumference is graduated to degrees. The base is provided with an oil rim.

A Circular Milling and Dividing Attachment is shown in Fig. 35. This attachment
Fig. 36 is adapted for use upon vertical spindle machines, or horizontal spindle machines in connection with the vertical spindle milling and slotting attachments. It has no automatic feed. When used with the vertical spindle milling attachment, the machine is fitted for all varieties of straight, surface and circular milling within its capacity, and with the slotting attachment, for all kinds of slotted work, such as die making, making templates, splining keyways, etc. Its design embodies the same features as the ones just Fig. 36 described, and, in addition, the index finger on the front of the attachment is adjustable to allow readings to be taken from any convenient graduation, and an adjustable dial graduated to read to 5 minutes, is fixed to the worm shaft. An index table mounted on the front of the base gives the degrees required for setting the table to produce work with 2, 3, 4, 5, 6, 8, 9, 10, 12, 15, 16, 18, 20 and 24 sides. This is particularly valuable for use in connection with the slotting attachment.

Fig. 37 High Speed Milling Attachment. Sometimes it is necessary in doing such work as milling keyways and slots, die making, etc., to use a small cutter, which should be run more rapidly than the fastest spindle speed available, otherwise it limits the production and is liable to be broken in feeding. In order to obtain correct speeds for these small mills, high speed milling attachments are employed. Fig. 36 shows one of these attachments for use on a vertical spindle milling machine, and Fig. 37 one designed for
Fig. 38 horizontal spindle machines. The construction in each case can be readily understood, as it consists of nothing other than a pair of gears for increasing the speed and an auxiliary spindle that drives the cutter.

Slotting Attachment. This attachment, shown in Fig. 38, is largely used in tool making, such as in forming box tools for screw machines, making templates, splining keyways, and work of a similar character. The working parts consist of a tool slide that is driven from the machine spindle by an adjustable crank that allows the stroke to be set for different lengths. The attachment can be set at any angle between and 90°, either side of the centre line, the position being indicated by graduations on the circumference of the head. The tool is held in place by a clamp bolt, and a tool stop that swings over the top of tool shank makes it impossible for the tool to be pushed up.

Fig. 39 Attachment for Cutting Short Leads. In cutting spirals with a spiral head, as the lead becomes shorter and a higher ratio of gearing becomes necessary, the stress upon the gears and mechanism becomes greater. For this reason, it is impractical to cut very short leads in this way. The attachment shown in Fig. 39 is designed particularly for use when it is desired to cut short leads.

It consists of a casting clamping over the dovetail of the spiral head carrying a swiveling gear plate and a short shaft which is driven from the rear of the machine spindle by a belt.

The work is rotated from the spindle independently of the feed screw, the latter being disconnected from the power feed mechanism.
Fig. 40 The regular index change gears are used on the swiveling gear plate to connect with the large index gear to give the work the proper speed of rotation. The lead is obtained as described on pages 58 to 63, allowing the rotation of the work to drive the table feed screw. Eighteen holes in the large index gear allow indexing when cutting multiple threads.

A rack cutting attachment or vertical spindle milling attachment is used to drive the cutter.

Spiral Milling Attachment. This attachment, shown in Fig. 40, is designed for the heavy class of spiral cutting in conjunction with the spiral head. The cutter is placed on the end of cutter spindle, allowing attachments to cover a large variety of work. In addition to cutting spirals, attachments can be used for cutting racks. The spindle can be set at any angle in a horizontal plane.

Rack Cutting Attachment. An attachment for cutting teeth in racks is shown in Fig. 41. It can also be used in connection with the spiral head for cutting worms, on Universal Milling Machines, as shown on page 173, and for other miscellaneous operations.

Fig. 41 The cutter is mounted on the end of a hardened steel spindle that extends through the attachment case parallel to the table T slots. This spindle is powerfully and smoothly driven from the machine spindle by a train of hardened steel bevel and spur gears.

A vise, the construction of which can be plainly seen in the cut, is furnished as a part of the attachment.

When cutting racks, some convenient means of indexing to quickly and accurately space the teeth is
Fig. 42 necessary. Fig. 42 shows an indexing attachment designed for this purpose. It consists of a bracket that is fastened in the table T slot at the left-hand end. The bracket carries a locking disk, together with change gears for gearing to the feed screw. To index any required spacing, * change gears are selected that Fig. 42 will produce one or more whole turns of the locking disk. For each division the locking pin is withdrawn and the table advanced by the crank on the feed screw until the pin drops into the slot again, and locks the disk. This method of indexing is therefore much easier than relying upon a dial such as ordinarily used for the purpose.

Tilting Table. A handy attachment, known as a Tilting Table, is shown in Fig. 43. It is designed primarily for use in connection with index centres when fluting taper reamers, taps, etc. In addition to this work, many other kinds of taper pieces can be accurately reproduced. Its general characteristics, the manner in which it is fastened to the table, and the way that it is elevated, are all clearly shown in the cut.

Fig. 43

Cam Cutting Attachment. The Cam Cutting Attachment, shown in Fig. 44, is used for cutting either Face, Peripheral or Cylindrical Cams from a flat former. The former is made from a disk about 1/2 inch thick, on which the required outline is laid out. The disk is machined or filed to the required shape.

The table of the machine remains clamped in one position during cutting, and the necessary rotative and longitudinal movements are contained in the mechanism itself. The rotative movement is obtained by a worm driving a wheel fixed to the spindle of the attachment. The former is secured to the face of the worm wheel, and as the wheel revolves, the former depresses a sliding rack that

Fig. 44

Fig. 45

in turn drives a pinion geared to another rack in the sliding bed of the

attachment, thus giving the necessary longitudinal movement. In the cut the former is shown in position on the face of the worm wheel.

The attachment is sometimes driven automatically by means of a round belt leading from a small jack-shaft to a three-step cone pulley fastened on the end of the worm shaft. The pulley is clutched to the worm so that either hand or automatic feed may be used by the simple movement of a lever. Illustrations of the use of this attachment are to be found in Chapter IX.

Scales and Verniers for Milling Machines. Scales and verniers are useful on such work as boring jigs, fixtures, or wherever extreme accuracy is required and it is necessary to make fine adjustments of the table. The scales are graduated to 40ths of an inch, and the verniers read to thousandths of an inch. A machine with all of the table adjustments fitted with scales and verniers is shown in Fig. 45.

Spring Chucks. Fig. 46 shows an unassembled spring chuck. This chuck is convenient for holding wire, small rods, straight shank drills, mills, etc. The collet holder is of steel, ground to fit the standard taper hole of the machine spindle, and has a hole its entire length. The front end is fitted to receive a spring collet, which is held in place by a cap nut that forces it against the taper seat and closes the chuck centrally. A nut is provided for withdrawing the collet holder from the spindle.

In addition to the attachments already mentioned in this chapter, there are many minor fixtures frequently used in milling operations. These are spoken of in connection with general notes on milling in Chapter VII.

Fig. 46

Heavy Manufacturing Milling Machine