54 MACHINERY. October, 1901.

by comparatively unskilled help, with the certainty that each and every part finished will be perfectly interchangeable, as the sizing does not depend on the pressure of the operator’s hand on the cross-slide lever, as is the case when the ordinary toolpost-forming tool is used.

By the use of the tools and fixtures here shown, a large number of different shaped castings were finished, all that is necessary for a change being to fit a different forming tool to the holder. The output from the machine to which the fixtures were affixed was increased three-fold, and the expense reduced accordingly.

Editor MACHINERY:

% inch wide, and so on, the number of different sizes of

keyways being determined by the number of pairs of scribers

on the head. At M, Fig. 2, the head F is shown marking

out a keyway on the gear seat. At each end of the shaft is

a keyway for a crank disc. As may be seen in Fig. 4 the

~

Fig. 4.

keyways in the crank discs are diametrically opposite the crank pins, so that after they are pressed onto the shaft the crank pins will come 120 degrees apart.

FORMED MILLING CUTTERS.

Editor MAcnINmiv:

               ‘rhe economy in time and accuracy of results obtained by the use of milling cutters, adapted to be ground without changing their shape, is very well known to mechanics, the cutting of gears and duplicating of irregular shapes in milled work having, indeed, become dependent upon them. However, the cost of a single cutter formed to a new shape is likely

an angle of 60 degrees from the vertical. Each rod is supported at its end farthest from the yoke by a link or arm, as shown at C and D, which links have projecting centers that enter the centers in the ends of the shaft. The projecting center in link C is capable of adjustment in order to bring the fixture firmly into position against the centers. Each link is keyed onto its rod so that its axis passes through the keyway on the rod, making the links set at an angle of 60 degrees with vertical, as shown in Fig. 1. Then, in order to adjust the fixture vertically to bring the projecting centers in line with the shaft centers, the guide rest E is made adjustable through the yoke by means of setscrew T.

For carrying the scribers a sliding head is provided upon each rod, as shown at F and G, Fig. 2, with keyways and keys. To each head are bolted several scribers of shape shown in Fig. 4. These scribers are separated into two bunches upon each head, the two inner ones being just 1/5 inch apart; thus when they are swung down into position they will mark

to be regarded as excessive, as such is necessarily special in its nature. Yet any shop possessing a lathe and milling machine need apprehend no excessive difficulty in producing satisfactory formed cutters at an expense little greater than that of ordinary milling cutters of corresponding sizes, provided they will do a little preliminary rigging-up for the purpose, as follows:

Every original form of cutter should have its template, shaping tool and lathe tool. The template may be a thin piece of sheet metal, preferably steel, having its edge worked to the desired form of the finished cut, either from a model or drawing. The shaping tool may be cast steel, with a shank to fit the fly tool holder of the milling machine, or the tool post of the shaper, its cutting end having a clearance angle of about 15 degrees from the top, or cutting edge. The cutting edg of this tool must be fitted accurately to the template, when the two are held in the same plane, and its depth of face must be enough to insure sufficient strength and vi~-i~Utv +‘-~ "‘~~l’

Fig. 3

ii

October, 1901. MACHINERY

Pg55

enables both to be held readily in the same plane and allows the light to show, progress in fitting together. The lathe tool should be machined all over to get the sides parallel and surfaces square with each other. Its cutting end will of course, be made of sufficient width to fully cover the with of the cutter upon which it is to operate, and in order to work well it must be held square, both in receiving its shape, and in forming the cutter. The straight sides will aid materially in this and also in setting the tool at the proper angle with the shaping tool while its cutting face is prepared by it, and later in setting it radial with the cutter blank center. These steps are necessarily performed where the cutter is made, as also must be performed the preparation of the cutter blank, including rough turning to shape and the gashing of the teeth.

Occasionally a shop, driven by necessity, and at the same time recognizing the unreliability of hand-filed and scraped cutters, makes use of a special eccentrically-centered arbor, with a hand lever attachment for baking off, and backs off the cutters thus one tooth at a time. This is better than an attempt at filing, but it is hard work, and the lengths of the teeth are liable to vary as each tooth is independently finished. Further, as the cutter blank raises and lowers, by reason of the eccentricity of the arbor, the center of the cutter is constantly changing its position relative to the top of the lathe tool, so that the shape imparted to it will be modified by the throw of the arbor, and hence will not be exactly correct; neither will the tooth be quite the same at the point and heel, successive grindings showing a difference of cut, which Is more perceptible in a cutter having considerable difference in its face outline than in one of a nearly uniform diameter.

The Balzer relieving device is an improvement over the plain eccentric arbor in some respects, as it performs the desired work automatically and uniformly, and the teeth are formed more nearly correct, as may be understood from the following description of the device. The diagram, Fig. 1, shows a sectional view of the apparatus as applied to an ordinary lathe,

Rt top

P, being the faceplate and R the tool post. A is a shouldered arbor eccentrically centered to give the required amount of lateral motion, or throw, to the cutter blank, 1, to and from the tool C, by which it is formed, and relieved or backed off. The sleeve B turns freely on the arbor, between its shoulder and the nut K, and at its rear end is rigidly secured the gear C, while the loose gear H turns freely beside it. In practice, however, the gear H is kept from turning by the lever I, which rests on any stationary object, as the lathe bed or its carriage. The cutter, previously gashed, is held firmly between collars on the outer end of the sleeve B, which are clamped by the nut L. E is a driving lever secured to the arbor A and connected to it is the stud D, one end of which engages with the face plate, while the other end forms a bearing for the loose running pinion F.

It may be seen that if the gear wheels G and H had the same number of teeth, no motion would be imparted to them, or to the sleeve B. but the whole would have only the eccentric throwing action due to the arbor A. In practice C has the same number of teeth as H for about half of its circumference, but a few less on the other half:; consequently the sleeve B and the cutter have a forward motion timed to take place when the eccentric action of the arbor throws towards the cutting tool.

The cycle of operation is as follows: Starting with the cutting tool at the front edge of a tooth in the cutter, the latter is slowly rotated forward, and at the same time moved forward bodily towards the tool until the next gap is reached; then the cutter stops rotating, but begins to recede from the tool until time for the cut to begin on the next tooth, when the operation is repeated. The lathe is thus running steadily forward all the time, making as many revolutions as the cutter has teeth, while the cutter revolves but once during the whole work of relieving all the teeth. The device is weak, for obvious reasons, and limited to a certain number of teeth, relative to the gearing employed.

The relieving device, shown in Fig. 2, can be applied to any ordinary engine lathe, with modifications to suit the varying conditions. As may be seen, it is extremely simple, consisting of a cam 2, having one or more throws, fitted to the lead screw of the lathe and adapted to be driven by It, at any point along its length, as at the end of the carriage, or back of it underneath the apron, as may be preferred. Riding on this cam is a roller T, held in the lever U, to the outer end of which lever is attached a weight by means of the cord C. The other end of the lever U is secured to the short shaft V, supported by the brackets W, which are in turn fastened to the lathe carriage from beneath at B. Also on the shaft V is adjustably connected another lever X, forked at the top and engaging there between double flanged collars Y on the cross feed screw of the lathe in the place ordinarily occupied by a thrust nut, here temporarily removed. The common change gears for cutting threads are used in the same place and manner as originally designed. The brackets may be made a permanent attachment to the lathe, while the cam can remain on the lead screw without interfering in the least with its usual functions.

As the tool is, with this device, set at the height of the lathe center and as the device operates direct on the cross feed screw,

stantly changing its position relative to the top of the lathe tool, so that the shape imparted to it will be modified by the throw of the arbor, and hence will not be exactly correct; neither will the tooth be quite the same at the point and heel, successive grinding~ showing a difference of cut, which Is more perceptible in a cutter having considerable difference in its face outline than in one of a nearly uniform diameter.

The Balzer relieving device is an improvement over the plain eccentric arbor in some respects, as it performs the desired work automatically and uniformly, and the teeth are formed more nearly correct, as may be understood from the following description of the device. The diagram, Fig. 1, shows a sec

ported by the brackets W, which are in turn fastened to the lathe carriage from beneath at B. Also on the shaft V is adjustably connected another lever X, forked at the top and engaging there between double flanged collars Y on the cross feed screw of the lathe in the place ordinarily occupied by a thrust nut, here temporarily removed. The common change gears for cutting threads are used in the same place and manner as originally designed. The brackets may be made a permanent attachment to the lathe, while the cam can remain on the lead screw without interfering in the least with its usual functions.

As the tool is, with this device, set at the height of the lathe

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