A


It is Oct of 1914-1918, what is happening....Excerpt from Success in the Small Shop "Success in the small shop" is the reality worked out from a definite idea in technical journalism in the machinery-building field. Early in the year 1914, there came into the possession of the American Machinist a mass of statistical information in regard to the machine shops of the city of Cleveland, Ohio. /> .[15]
city of Cleveland, Ohio.="" /> top
sky
pic top
size
top
top
sky
pic top
size
Gear-Cutting-Machines-1908-ICS
 
alt="https://antiquemachinery.com/images-American-Machinist-Oct-29-1942/pg-1235-Armamet-Tank-Engines-made-on-Coverted-Equipment-Airplane-Engine-Vintage-Old-Antique-Equipment-Machine-Shop-Machines.jpeg" text pg 2

 GEAR–CUTTING. § 18 pg 10 
ordinary single cutters. When several cutters are thus placed, they are called gang cutters. They may be di-vided into two classes, which are : (a) Gang cutters that finish teeth to an approximate shape ; (b) gang cutters that finish teeth to exact shape. 
24. The Clough duplex cutter belongs to the first class, since one gang of two cutters made as shown in Fig. 2 (a) is used for all gears of the same pitch. For gears of more than 30 teeth, the teeth are finished entirely by the inside faces of the cutters, as shown in Fig. 2 (b) at a ; gears having a smaller number of teeth have the flanks of the teeth finished by the outside faces dOr the cutters, and the faces of 
(a) (b) 


FIG. 2. the teeth by the inside faces of the cutters, as shown at b in the same figure. Gears cut with these caters will have approximately involute teeth, and different gears .cut by the same cutter will run together fairly well. Their motion obviously cannot be as exact as that of wheels cut. by a cor-rect single cutter. These duplex cutters are laid out in such a manner that the wheels cut by them will mesh and 'run with gears cut with regular involute standa.rd cutters. 

 §18 GEAR–CUTTING. 11 
25. The Gould & Eberhardt gang cutter is an ex-% ample of a cutter belonging to the second class. If the teeth of a gear-wheel be examined, it will be found that usually several of them can be cut at once if the cutter is shaped to conform to the tooth out-lines. Thus, in Fig. 3, the cutter a conforms to the space a' the cutter b conforms to the space b', and as its central plane perpendicular to its axis of rotation passes through the axis of the gear, it is a standard cut-ter. Finally, the cutter c conforms to the space c'. By employing three gang cutters thus formed, three teeth can be cut at a time, Nrid, hence, the indexing would be done for three teeth instead of one 

FIG. 3. In 
consequence of this, a gear can be cut in less time than is required for cutting it with a single cutter, but owing to the increased heating it cannot be cut in one-third of the time. Since such gang cutters can have the correct shape for only one size ofi a gear, it follows that a separate gang is required for each size. The Gould & Eberhardt gang cutter is intended primarily for manufacturing—that is, making a large number of equal gears—and in its special field is obviously far ahead of the ordinary single cutter. The large number of gangs required to cover the whole range of gears of each pitch makes it rather unsuitable for jobbing work. 
MACHINERY AND ATTACHMENTS. 26. In the formed-cutter process, where a milling cut-ter is used, the gear may be cut either in a plain milling machine fitted with a suitable indexing attachment, or in a universal milling machine, or in a regular gear-cutting engine. 

e
small pic
alt=""
/images-Sucess-in-the-small-Shop/Success-in-the-Small-shop-1914-pg-85-Small-shop-Lineshafting-What-are-those-rings-running-along-the-metal shafts-up-there-Shaft-Pollishers-and-pulleys-leveling-aligning.jpeg
alt="http://antiquemachinery.com/images-2020/Machinery-Magazine-March-1896-vol-2-no-7-top-Cover-men-working-old-shop-lineshaft-belt-drive-1896%20(2).jpg" <

pg12 
GEAR—CUTTING. § 18 
27. Gear-Cutting Attachment. The simplest form of gear-cutting attachment dues not differ in principle from that of the plain index centers, except that the index plate has only one row of holes and thus a rather limited range of usefulness. Other attachments have a large index plate and a number of different rows of holes so as to extend their range of usefulness. Sometimes a still more elaborate device, like that shown in Fig. 4, is employed. In this the gear blank is mounted on a mandrel and placed between the cent4s a and h., or it may be mounted upon an arbor placed in the spindle in place of the center a. Inside of the guard c there is a worm-wheel which is operated by a worm on the shaft f , and the indexing is done by means of an index plate d. The device is 

FIG. 4. SO arranged that the worm upon the shaft can be disengaged from the worm-wheel in the case c, the worm-wheel rotated by hand, and a plain index pin used in the holes in the back of the plate. The attachment shown can ordinarily be used only for spur gears and sprocket wheels ; when fitted to a universal milling machine,•it can also be used for gashing worm-wheels. 28. When a universal milling machine is available, spur gears, worm-gears, sprocket wheels, screw gears, and bevel gears can be cut ; .but bevel gears can be cut only approxi-mately correct. 29. Gear-Cutting Engine.—.-A regular spur gear-cutting engine is only a special form of a milling machine, 

§ 18 
GEAR—CUTTING. 13 
and differs from it chiefly in that, as a general rule, the indexing and also the running back of the cutter is done automatically. Fig. 5 shows one form of an automatic spur gear-cutting engine built by Gould & Eberhardt, Newark, New Jersey. The gear blank is fastened in some suitable manner to the spindle a generally, an arbor is used, which, in the de-sign shown, is supported at its outer end by the adjustable 

FIG. 5. 
outboard bearing b. Upon the spindle is fastened a worm-wheel that is enclosed in a guard c in order to protect it a worm meshes with the worm-wheel and is in turn oper-ated by change gears that revolve it a definite part of a revolution each time the cutter is clear of the gear blank and before it begins to cut. The cutter is carried in a 

Pic 3

alt="https://antiquemachinery.com/images-American-Machinist-Oct-29-1942/pg-1237-Armamet-Tank-Engines-Airplane-made-on-Coverted-Vintage-old-Antique-Equipment-Baker-Rock-Island-Veteran-Drill-new-heavy-Fixture-Machine-Shop-Machines.jpeg" text pg 3

§ 18 

 

14-15. 

§ 18 
slide d that is moved parallel to the axis of the spindle a, and is fed automatically to the work and returned. The cutter is adjusted for depth by lowering the gear blank. A limited side adjustment is usually provided for the cutter to allow cutters of different thicknesses to be set central. 30. Automatic gear-cutting engines are often arranged so that they can be used for cutting approximately correct bevel gears. The slide that carries the cutter is then ar-ranged in such a manner that it can be set at the required angle to the axis of the spindle. 31. Change Geafing.—The gearing that revolves the shaft carrying the worm is, as a general rule, actuated by a so-called stop-shaft, which is provided with a suitable clutching mechanism operated by the cutter slide. This clutching mechanism is so arranged that it allows the stop-shaft to make exactly one revolution whenever the return-ing cutter slide unlocks it. The change gears that will produce a certain number of divisions are selected in ac-teeth in worm-wheel cordance with the ratio   In case of teeth to be cut simple gearing, this is the simple ratio that gears are to be selected for ; in case of compound gearing, it is the com-pound ratio, which is resolved into factors. The gears are selected in the same manner as is done in gearing a lathe for thread cutting or a milling machine for the cutting of helixes. In adjusting the gear-cutting engine, the tripping ar-rangement for the stop-shaft clutching mechanism must be set so that it will act only after the cutter on its return stroke is entirely clear of the gear. 
CUTTING BEVEL GEARS WITH FORMED CUTTERS. 32. Selecting the Cutter.-While bevel gears cut with a cutter of fixed curve can be only approximately cor-. rect, the comparative cheapness of this method ha`s led to its being largely used. The ordinary cutters made for spur 

§ 18 GEAR–CUTTING. 15 
wheels should never be used -for this purpose, as they will cut the teeth of the bevel gear entirely too thin at the small end. Special miter-gear and bevel-gear cutters are made for this purpose ; these cutters are of the involute form, but thinner than the standard cutters. They are numbered from 1 to 8, and cover the same range as the standard involute cutters. A bevel-gear cutter cannot be selected in the same manner as the ordinary spur-gear cut-ter, that is, directly in accordance with the number of teeth ,of the bevel gear. It is to be selected, instead, for a number of teeth that is calculated by one of the rules given below, the first of which is as follows: Rule. To find the number of teeth a bevel-gear cutter is to be selected for, divide the number of teeth of the bevel gear by the natural cosine of the center angle a d e, Fig. 6. EXAMPLE. — The center 4. angle of a bevel gear having 24 teeth is 53° 15'. What number of teeth should the cutter be selected for ? SOLUTION.—The cosine of 53° 15' is .59832. Applying the rule, we get  24 = 40 teeth. Referring to the Table of Standard Cutters, .59832 we find that for gears having between 35 and 54 teeth, a No. 3 cutter is to be used. Hence, use a No. 3 bevel-gear cutter. Ans. 33. When a drawing of the bevel gear is available, use the following rule: Rule. Measure the slant height of the back cone, as a b in Fig. 6; double: it and multiply by the diametral pitch. The product will be the number of teeth the cutter is to be selected for. EXAMPLE.—The slant height of the back cone being 5 inches, and the diametral pitch being 4, what number of bevel-gear cutter is to be used ? SOLUTION.—Applying the rule just given, we get 5 X 2 X 4= 40 teeth. Referring to the Table of Standard Cutters, it is seen that a No. 3 bevel-gear cutter is to be used.

Ans. 
34. Setting the Machine.-The cutter having been selected, place it on its arbor; put the gear blank into the 50 —36 

/images-American-School-Tool-Making-book/Tool-Making-p-138-139-grinding-an-angular-cutter.jpeg
  pa


Fig. 231. Fly-Cutter Arbor 

/images-American-School-Tool-Making-book/Tool-Making-p-138-139-grinding-an-angular-cutter.jpeg/images-American-School-Tool-Making-book/Tool-Making-p-138-139-grinding-an-angular-cutter.jpeg<b><span style="line-height: 22px;">&nbsp;<br>
GEAR–CUTTING. § 18&nbsp;<br>
GENERATION SYSTEM.&nbsp;<br>
CONJUGATE-TOOTH METHOD.&nbsp;<br>
MOLDING PROCESS.&nbsp;<br>
45. The different processes employed in the conjugate-tooth method of generating gear-teeth are all based on the so-called molding process, which has not been put into practical use, however, at least not to any extent. This process may be explained as follows : Let a correctly formed rack made of some hard material, as steel, be passed over a gear blank made of a plastic material, as beeswax, while the blank is given a positive rotation that imparts to it at the pitch circle a velocity equal to that of the rack. Then, the pitch line of the rack and the pitch circle of the blank being tangent, the teeth of the rack will mold teeth in the blank that are conjugate to its own.&nbsp;<br>
MOLDING-PLANING PROCESS. ■61) 46. Principle of Operation.-Since the materials of which gear-wheels are constructed are not plastic, the mold-ing process cannot be employed very readily, but the same effect can be produced by transforming the generating rack into a cutting tool that reciprocates across the blank in the direction of the axis of the latter. The cutting tool does not advance during its cutting stroke in a line tangent to the pitch circle of the blank and at right angles to the axis of the latter but, after the tool has cleared the blank on its return stroke, the tool and the gear blank are given a slight motion equivalent to that of a meshing rack and pinion and the tool is reciprocated through the blank again. This cycle of operations is repeated until the gear blank has been trans-formed into a gear. The molding process thus becomes the&nbsp;<br>
§ 18&nbsp;<br>
•&nbsp;<br>
GEAR–CUTTING. 23&nbsp;<br>
molding-planing process in execution, however, this proc-ess is modified for practical reasons, the chief of which are the great length of rack required and the difficulty of making it.&nbsp;<br>
47. Fellows Gear-Shaper.—In the Fellows gear-shaper, in which machine the molding-planing process is employed, the cutter a, Fig. 11, is made in the form of a gear. The process by which the cutter is generated is equivalent to its generation by an involute rack, and it is&nbsp;</span></b>/images-American-School-Tool-Making-book/Tool-Making-p-138-139-grinding-an-angular-cutter.jpeg

          

page 16-18  GEAR-CUTTING. 
machine, and set the latter to the set the cutter central in respect to 

FIG. 6. 
cuts b or c at the small, side of the tooth a. Next, set the cutter off center to the other side of the center by the same amount and roll the blank toward the cutter again until it enters the other central slot at the small end. Take the cut, and measure the thick-ness of the tooth a at the pitch line at the large end. If its thickness is more than the quotient 
end of the 
§ 18 
cutting angle. Now, the gear blank ; then set it to the cor-rect depth of cut, measuring at the large end of the blank, and cut two adjacent tooth spaces, as b and c in Fig. 7, which leaves the tooth a rather too thick. Set the cutter off center an amount equal to about TIT, the thickness of the tooth a at the large end. Now, revolve the gear blank toward the cutter until the latter will enter one of the central gear and cut the one $111 

§ 18 FIG. 7. 
GEAR-CUTTING. 17 
obtained by dividing the circumference of the pitch circle by twice the number of teeth, it shows that the cutter must be set farther off center. This having been done, the blank is rolled toward the cutter and both sides of the tooth a are cut again, and the cycle of operations is repeated until the tooth is of the correct thickness at the large end. The gear blank can now be cut, first setting the cutter off center one way the amount determined by trial and cutting all around the gear, and then setting it off center the other way and going around once more. 


35. The method given in Arts. 32, 33, and 34 will answer fairly well for teeth that are shorter than the slant height of the pitch cone ; it will leave the teeth correct at the large end, but not rounding enough at the small end. The teeth must consequently be dressed with a file.

404 36. Gear-Tooth Caliper. —A good form of a caliper for measuring the thickness of the gear-teeth is shown in Fig. 8. The vertical slide a is first set until the reading of 


FIG. 8. 
its vernier is equal to the calculated addendum of the tooth ; the caliper is then applied to the gear with the slide a resting on top of a'gear-tooth, as shown, and the horizontal jaw b is 

-------------------------------here--3-20-24------------------- -------------------------------here--3-20-24--------------------------- -----------------------here--3-20-24-------------------
  /images-American-School-Tool-Making-book/Tool-Making-p-138-139-grinding-an-angular-cutter.jpeg
---------
 

 

1
GEAR–CUTTING. § 18 
brought against the tooth. The thickness of the tooth is read on the horizontal vernier. 
37. General Instructions.—When miter gears are cut, both gears of a pair are cut with the same cutter when bevel gears are cut, the proper number of the cutter should be computed for each by the rules previously given. If the cutting is done in a machine where the angle between the axis of the index-head spindle and the axis of the cutter spindle can be changed, the angle should be made 90° before beginning to set the machine. This gear-tooth caliper does not give good results when applied to the teeth of small pinions unless care is taken to see that the points of the jaws are in contact with the pitch points of the teeth. This may necessitate the setting of the vertical scale to a greater distance than the addendum.

 
RACK CUTTING. 
38. A rack may be cut either with a planing tool or a milling cutter shaped to conform to the rack teeth. The pitch of the rack is equal to the pitch of the spur gear mesh-ing with it, and since cut spur gears are made almost en-tirely to the diametral-pitch system, the circular pitch must usually be computed from it to obtain the spacing. 39. Short racks can readily be cut in the horizontal milling machine, using the cross-feed screw to obtain the spacing and the regular longitudinal-feed screw for feeding. The rack blank may either be clamped to the table or be held in the vise or in a special fixture. 40. Racks that are too long to be cut in this manner can be cut by means of a special rack-cutting attachment, one form of which is shown in Fig. 9. The cutter a is placed at right angles to its normal position this allows the feed-screw b to be used for spacing the teeth and the cross-feed screw for feeding. A graduated dial c reading to .001 inch is placed on the feed-screw, and the correct 

§ 18 
GEAR–CUTTING. 19 
spacing is obtained by means of it. The rack may be placed in a fixture d made as shown, which will take several racks at one time. 
41. When racks are cut in the milling machine, it is strongly recommended that the gibs of the part that is moved in order to obtain the spacing be set up more firmly than usual in order to create enough friction to prevent any shifting, which is liable to occur by reason of the backlash of the feed-screw. 

FIG. 9. 
Racks are often cut in milling machines of the planer type ; in that case, the spacing is obtained by means of the feed-screw in the cross-rail. The head should then have its gibs set up rather firmly. The rack is placed square across the platen. A planing tool formed to the correct shape may be used in a planer, shaper, or slotter, obtaining the spa-cing by means of whatever feed-screw can be used for the purpose, 

 

---------
 

 

18 20 
GEAR-CUTTING.

 
GEAR–CUTTING. § 18 
GENERATION SYSTEM. 
CONJUGATE-TOOTH METHOD. 
MOLDING PROCESS. 
45. The different processes employed in the conjugate-tooth method of generating gear-teeth are all based on the so-called molding process, which has not been put into practical use, however, at least not to any extent. This process may be explained as follows : Let a correctly formed rack made of some hard material, as steel, be passed over a gear blank made of a plastic material, as beeswax, while the blank is given a positive rotation that imparts to it at the pitch circle a velocity equal to that of the rack. Then, the pitch line of the rack and the pitch circle of the blank being tangent, the teeth of the rack will mold teeth in the blank that are conjugate to its own. 
MOLDING-PLANING PROCESS. ■61) 46. Principle of Operation.-Since the materials of which gear-wheels are constructed are not plastic, the mold-ing process cannot be employed very readily, but the same effect can be produced by transforming the generating rack into a cutting tool that reciprocates across the blank in the direction of the axis of the latter. The cutting tool does not advance during its cutting stroke in a line tangent to the pitch circle of the blank and at right angles to the axis of the latter but, after the tool has cleared the blank on its return stroke, the tool and the gear blank are given a slight motion equivalent to that of a meshing rack and pinion and the tool is reciprocated through the blank again. This cycle of operations is repeated until the gear blank has been trans-formed into a gear. The molding process thus becomes the 
§ 18 
• 
GEAR–CUTTING. 23 
molding-planing process in execution, however, this proc-ess is modified for practical reasons, the chief of which are the great length of rack required and the difficulty of making it. 
47. Fellows Gear-Shaper.—In the Fellows gear-shaper, in which machine the molding-planing process is employed, the cutter a, Fig. 11, is made in the form of a gear. The process by which the cutter is generated is equivalent to its generation by an involute rack, and it is 

FIG. 11. 
given teeth conjugate to those of the generating rack. In consequence of the method by which the cutter .is formed, the teeth of all gears cut by it are conjugate to the rack and hence to one another that is, the different gears will run together correctly. 

-------

/images-American-School-Tool-Making-book/Tool-Making-p-138-139-grinding-an-angular-cutter.jpeg

----A Gleason Gear Template I Have------8- tooth for the 54 inch machine  20 degree involute system----Machine  ca 1900 that  I have-----

 3-20-24


GEAR–CUTTING. § 18  pg 22-23
GENERATION SYSTEM. 
CONJUGATE-TOOTH METHOD. 
MOLDING PROCESS. 
45. The different processes employed in the conjugate-tooth method of generating gear-teeth are all based on the so-called molding process, which has not been put into practical use, however, at least not to any extent. This process may be explained as follows : Let a correctly formed rack made of some hard material, as steel, be passed over a gear blank made of a plastic material, as beeswax, while the blank is given a positive rotation that imparts to it at the pitch circle a velocity equal to that of the rack. Then, the pitch line of the rack and the pitch circle of the blank being tangent, the teeth of the rack will mold teeth in the blank that are conjugate to its own. 
MOLDING-PLANING PROCESS. ■61) 46. Principle of Operation.-Since the materials of which gear-wheels are constructed are not plastic, the mold-ing process cannot be employed very readily, but the same effect can be produced by transforming the generating rack into a cutting tool that reciprocates across the blank in the direction of the axis of the latter. The cutting tool does not advance during its cutting stroke in a line tangent to the pitch circle of the blank and at right angles to the axis of the latter but, after the tool has cleared the blank on its return stroke, the tool and the gear blank are given a slight motion equivalent to that of a meshing rack and pinion and the tool is reciprocated through the blank again. This cycle of operations is repeated until the gear blank has been trans-formed into a gear. The molding process thus becomes the 
§ 18 
• 
GEAR–CUTTING. 23 
molding-planing process in execution, however, this proc-ess is modified for practical reasons, the chief of which are the great length of rack required and the difficulty of making it. 
47. Fellows Gear-Shaper.—In the Fellows gear-shaper, in which machine the molding-planing process is employed, the cutter a, Fig. 11, is made in the form of a gear. The process by which the cutter is generated is equivalent to its generation by an involute rack, and it is 

FIG. 11. 
given teeth conjugate to those of the generating rack. In consequence of the method by which the cutter .is formed, the teeth of all gears cut by it are conjugate to the rack and hence to one another that is, the different gears will run together correctly. 

GEAR–CUTTING. § 18  pg 22-23
GENERATION SYSTEM. 
CONJUGATE-TOOTH METHOD. 
MOLDING PROCESS. 
45. The different processes employed in the conjugate-tooth method of generating gear-teeth are all based on the so-called molding process, which has not been put into practical use, however, at least not to any extent. This process may be explained as follows : Let a correctly formed rack made of some hard material, as steel, be passed over a gear blank made of a plastic material, as beeswax, while the blank is given a positive rotation that imparts to it at the pitch circle a velocity equal to that of the rack. Then, the pitch line of the rack and the pitch circle of the blank being tangent, the teeth of the rack will mold teeth in the blank that are conjugate to its own. 
MOLDING-PLANING PROCESS. ■61) 46. Principle of Operation.-Since the materials of which gear-wheels are constructed are not plastic, the mold-ing process cannot be employed very readily, but the same effect can be produced by transforming the generating rack into a cutting tool that reciprocates across the blank in the direction of the axis of the latter. The cutting tool does not advance during its cutting stroke in a line tangent to the pitch circle of the blank and at right angles to the axis of the latter but, after the tool has cleared the blank on its return stroke, the tool and the gear blank are given a slight motion equivalent to that of a meshing rack and pinion and the tool is reciprocated through the blank again. This cycle of operations is repeated until the gear blank has been trans-formed into a gear. The molding process thus becomes the 
§ 18 
• 
GEAR–CUTTING. 23 
molding-planing process in execution, however, this proc-ess is modified for practical reasons, the chief of which are the great length of rack required and the difficulty of making it. 
47. Fellows Gear-Shaper.—In the Fellows gear-shaper, in which machine the molding-planing process is employed, the cutter a, Fig. 11, is made in the form of a gear. The process by which the cutter is generated is equivalent to its generation by an involute rack, and it is 

FIG. 11. 
given teeth conjugate to those of the generating rack. In consequence of the method by which the cutter .is formed, the teeth of all gears cut by it are conjugate to the rack and hence to one another that is, the different gears will run together correctly. 


position:absolute="">   

pg 144/images-American-School-Tool-Making-book/Tool-Making-p-138-139-grinding-an-angular-cutter.jpeg

  page 134-135  TOOL-MAKING 

134 TOOL-MAKING 
cutter should be taken from the oil and heated sufficiently to prevent cracking from internal strains, then brightened, and the temper drawl to a straw color. Spiral Milling Cutters. It is customary in most machine shops to make all milling cutters of more than 2-inch face with teeth cut spirally as in Fig. 202. The amount of spiral given the teeth varies in different shops and on different classes of work. The object of spiral teeth is to maintain a uniformity of cutting duty at each instant of time. With teeth parallel to the cutter axis.. the tooth, on meeting the work, takes the cut its entire length at the same instant, and the springing of the device holding the work and of the cutter arbor causes a jump to the work. If the teeth are 

Fig. 202. Milling Cutter with Spiral Teeth Courtesy of Brown and Sharpe Manufacturing Company, Providence, Rhode Island 
cut spirally, the cut proceeds gradually along the whole length of the tooth; and after it is started, a uniform cutting action is maintained, producing smoother work and a truer surface, especially in the case of wide cuts. Milling cutters may be cut with either a right- or a left-hand spiral or helix, although it is generally considered good practice to cut a mill having a wide face with a spiral that will tend to force the cutter arbor into the spindle rather than to draw it out; then, again, it is better to have the cutting action force the solid shoulder against the box, rather than draw the adjusting nut against the box. Where two very long mills are used on the same arbor and it is found necessary to cut them with a quick spiral, one cutter is some-times made with a right-hand spiral and the other with a left-hand 
TOOL-MAKING 
135 
spiral, in order to equalize the strain and to reduce the friction result-ing from the shoulder of the spindle pressing hard against the box. Special care should be taken in cutting spiral milling cutters to see that the work does not slip. When a cut has been taken across the face of a cutter, it is best to lower the knee of the milling machine, thus dropping the work away from the mill while coming back for another cut; the knee can then be raised to its proper posi-tion, which is determined by means of the graduated collar on the elevating shaft of the machine. As it is important that the face of the cutting tooth be radial and straight, it will be found necessary to use an angular cutter of the form shown in Fig. 203, since cutters of this form readily clear the radial face of the cut and so remain sharp longer and produce a smoother surfact to the face of Fig. 2f0o3r. srAirnagluW;IFutter the tooth than an angular cutter of the form used for cutting teeth which are parallel to the cutter axis. The angular cutters for spiral mills are made with either 40 degrees, 48 degrees, or 53 degrees on one side, and 12 degrees on the other. By setting the cutter, as shown in Fig. 203, so that the dis-tance A is one-twelfth the diameter, the face cut by the 12-degree side of the angular cut-ter will be nearly radial for the usual propor-tions. The setting for cutting the teeth of a spiral cutter must be made before turning the spiral bed to the angle of the spiral. Nicked Teeth. Spiral cutters with nicked teeth, Fig. 204, are especially adapted for heavy milling. As the chip is broken up, a 


Fig. 204. Spiral Cutter with Nicked Teeth Courtesy of Becker Milling Machine Company, Hyde Park, Massachusetts 

/images-American-School-Tool-Making-book/Tool-Making-p-138-139-grinding-an-angular-cutter.jpeg

137-137 TOOL-MAKING 
If many formed mills are to be made, it is advisable to procure or make a machine specially designed for relieving—backing off—the teeth. As such machines are heavy and rigid, large cutters may be relieved and a smooth cut obtained, which is not possible with a light machine. Backing-Off Lathe Attachments. Although this style of cutter can be made to better advantage in a shop equipped with machinery designed especially for this class of work, an ordinary engine lathe 

Fig. 220. Balzar Backing-Off Attachment 
can be converted into a backing-off lathe for relieving or backing off the cutters. There are several commercial devices for the work : one comparatively inexpensive fixture is known as the "Balzar" backing-off attachment, Fig. 220; another arrangement consists simply of an eccentric arbor operated by a hand lever; or, a stud may be screwed into the faceplate of a lathe and the cutter placed on this stud 136
  
 

 

stop div id="e53-Pic- 

stop do it again

p

          pg 136-137

/images-American-School-Tool-Making-book/Tool-Making-p-138-139-grinding-an-angular-cutter.jpeg

 

page 148 TOOL-MAKING  Locating Cutter Tooth for backing off tools on faceplate./images-American-School-Tool-Making-book/Tool-Making-p-138-139-grinding-an-angular-cutter.jpeg           136 TOOL-MAKING 
much heavier cut can be taken than would be possible with an ordi-nary cutter. The nicking may be done as follows: An engine lathe is geared to cut a thread of the required pitch—two threads to the inch will be found satisfactory—and   with a round-nosed tools inch wide,   a thread is cut of a depth that will   not grind out before the teeth become too shallow to allow further grinding. This thread should be cut before mill-ing the spaces to form the teeth. Milling Cutters with Interlocking Teeth. When two milling cutters of an equal diam-eter are to be used 'on the same arbor in such a manner that the end of one cutter is against the end of the other, the corners of the cutting teeth are likely to break away, leaving a pro-jection—or fin—on the work, as shown in Fig. 205. In order to overcome this, part of the teeth are cut away on the sides of the cutters; that is, a tooth is cut away on one cutter, and the corresponding tooth on the other cutter is left full length to set into the recess formed by the cutting away of the tooth. In some shops it is customary to cut away every other tooth; while in others, two, three, or four teeth will be cut away and an equal number left. Fig. 206 represents a pair of mills hav-ing every other tooth cut away, while Fig. 207 represents a pair having four teeth cut away. In order to cut away the teeth to make a cutter with interlocking teeth, the cutter should be placed on a plug or an expanding arbor, as described for milling teeth on the sides of side milling cutters. By means of a milling 
Fig. 205. Badly Made Mill 

Fig. 206. Pair of Mills with Alternate Teeth Cut Away Courtesy of Brown and Sharpe Manufacturing Company, Providence, Rhode Island 

Fig. 207. Interlocking Cutters with Four Teeth Cut Away Courtesy of Union Twist Drill Company, Ahtol, Massachusetts 
TOOL-MAKING 137 
cutter having the proper width, the teeth may be milled away, although, in the case of a cutter having several teeth cut away, Fig. 207, it is well to use a narrow cutter, and after taking one cut, to turn the index head so that the next tooth is in position. This should be continued until the desired number of teeth have been cut away, after which the index head should be turned to pass over the required number of teeth, and the operation repeated. It is necessary, when making cutters with interlocking teeth (sometimes called dodged teeth) that the milling be deep enough to prevent the corresponding tooth on the other part of the cutter from 
ing the bottom of ecess. The parts of cutter should bear ist each other on shoulders, or hubs. Cutters for Milling >. An excellent form utter to be used for work as milling can be made as rn in Fig. 208. This is less expensive L one having interlocking teeth and answers the purpose as well. necesssary to make an eccentric mandrel of the design shown in 209, having the eccentric centers on opposite sides of the regular ers. The two pieces which make the cutter should be cut from bar long enough to finish the thickness of the heaviest part 
strik the r1 the agair the 
Slots of cu such slots ohm form than It is Fig. cent the 
AA the 
Ing. fore of t 

Fig. 208. Milling Cutter for Slots 
49 
Fig. 209. Eccentric Mandrel for Slot Cutters 
, Fig. 208. The hole is made 2-6 inch smaller than finish size, outside surface turned off, and the pieces annealed. After annealing, the hole is made the size desired for grind-One of the pieces is then placed on the eccentric mandrel, ed on until the side that is to be beveled is exactly in the center he mandrel. The side B may be machined with the mandrel 

/images-American-School-Tool-Making-book/Tool-Making-p-138-139-grinding-an-angular-cutter.jpeg

ppage 144 TOOL-MAKING 
     If many formed mills are to be made, it is advisable to procure or make a machine specially designed for relieving—backing off—the teeth. As such machines are heavy and rigid, large cutters may be relieved and a smooth cut obtained, which is not possible with a light machine. Backing-Off Lathe Attachments. Although this style of cutter can be made to better advantage in a shop equipped with machinery designed especially for this class of work, an ordinary engine lathe 

Fig. 220. Balzar Backing-Off Attachment 
can be converted into a backing-off lathe for relieving or backing off the cutters. There are several commercial devices for the work : one comparatively inexpensive fixture is known as the "Balzar" backing-off attachment, Fig. 220; another arrangement consists simply of an eccentric arbor operated by a hand lever; or, a stud may be screwed into the faceplate of a lathe and the cutter placed on this stud in a position that allows the teeth to be given the necessary amount of clearance. 


TOOL-MAKING 145 
When backing off the teeth of cutters whose faces do not exceed one inch in width, the Balzari backing-off fixture can be used to advantage. This device is held between the centers of a lathe in, 

Fig. 221. Special Arbor for Backing Off 
the ordinary manner, the backing off being such that the cutter can be ground without alteration of shape. The tool is so constructed that it is only necessary to place the cutter upon the arbor in the ordinary way. Place the arbor on the lathe centers as shown, start the lathe, and feed the forming tool in by the cross-feed screw in order to take the desired cut, in the same manner as in plain turning. The ratchet connected with the arbor and actuated by the pawl, contains ordinarily 36 teeth, and the stroke can be set to back off a cutter with 9, 12, 18, or 36 teeth.

Backing Of by an Eccentric Arbor. An arbor may be made having a pair of centers located to give the cutter tooth the required amount of clearance; such an arbor is shown in Fig. 221. The eccentric centers are shown at the sectional portions at the ends. The amount of eccentricity depends somewhat on the size of the cutter to be backed off, but for cutters not exceeding 4 inches in diameter, from to / inch will give excellent results. The screw at the end of the arbor should be of a fine pitch, about 12 threads per inch for arbors one inch in diameter. The object in 
ifiril 1.m  

".4 
Fig. 222. Eccentric Arbor fcr Backing-Off Cutter cutting a fine-pitch thread is that the cutter, being backed off, can be hold more securely with the same amount of force exerted in tightening the nut; again, the depth of the thread is not so great as 

 

/images-American-School-Tool-Making-book/Tool-Making-p-138-139-grinding-an-angular-cutter.jpeg

TOOL-MAKING  page  148-149 

page 148 TOOL-MAKING 
     brought down upon the carriage, the tooth of the cutter is brought down upon the sheet metal, and the nut is tightened. The tooth to be backed off is the one below that set to the thickness of the strip above the tool. The object in raising the tooth a given distance above the face is to prevent striking the tool at the end of the stroke. This operation must be repeated for the setting of each tooth before backing off. The forming tool is fed by means of the cross-feed screw; a tooth is backed off nearly the desired amount, leaving a little for a finish cut; the tool is withdrawn, the nut 

emill itill  
III Fig. 227. Method of Locating Cutter Tooth for Backing Off loosened, and the cutter turned on the arbor to bring the next tooth in position to be backed off, this operation being repeated until all the teeth are backed off alike. The amount of backing off must be determined by the cross-feed stop or by a graduated dial on the cross-feed screw. After the roughing cut has been taken on all the teeth, the forming tool should be sharpened by grinding or by oil-stoning, and the finish cut taken on the teeth. Backing Of by Stud in Faceplate. Another method of backing off cutter teeth is shown in Fig. 228. A stud is screwed in the face-plate of a lathe near the outer edge, as shown. The cutter, which must be a fit on the stud, is claniped by means of the nut. The finger 


TOOL-MAKING 149 
     A is movable in the slot in the stationary block B, which is so located on the faceplate as to bring the tooth. to be backed off into its proper location, and to keep it from turning during the operation. The forming tool is fed in gradually until the tooth is formed. The finger is then disengaged from the space in the cutter, which is revolved by means of the set screw until the next tooth is in position. Each tooth is machined separately; that is, the forming tool is fed in the required distance for each tooth when it is in position, the cutter is turned until the next tooth is in position, and the process repeated until each tooth has been backed off. In backing off cutters in this 

Fig. 228. Set-Up for Backing Off Cutter on Faceplate device, it is necessary to cut the notches (the spaces between the teeth) somewhat wider than the teeth. General Directions for Backing Off. When backing off the teeth for clearance by any of the means described, it is first necessary to form the blank, then to gash it or to cut the notches as described; then to back off the teeth. After backing off, it is necessary to mill the face of the tooth back 322 inch or so, to cut away the "jump", as it is termed, caused by the forming tool drawing in a trifle when it first strikes the edge of the tooth. ' Cutters of this description are sharpened by grinding on the face of teeth, as shown in Fig. 229. Milling Cutters with Threaded Holes. It is often necessary to make milling cutters with threaded holes. This happens in the case 

 

TOOL-MAKING  page  150-151   

150 TOOL-MAKING 

of small angular cutters, and in many styles of cutters for use on profiling (edge milling) machines. The general instructions given for making the other forms of cutters apply to those with threaded holes, except that instead of 
TOOL-MAKING pg 151 

trifle, say one thread. This allows the outer end to be squared up without mutilating the threads on the arbor. The reason for using the taper end of the arbor when squaring the first end of the cutter is that the shoulder is true with the thread in the cutter. After squaring this shoulder, the cutter blank may be removed and placed on the opposite end of the arbor with the side that has been squared against the shoulder of the arbor. This method of machining pieces of work having a threaded hole, where it is desirable that the outer surfaces be true with the hole, is applicable to all classes of work. The cutter may be machined to length and shape on the straight end of the arbor. Fly Cutters. The simplest form of milling machine cutter is known as a fly cutter. It has only one cutting edge, but is particu-


Fig. 229. Method of Grinding Formed Cutters reaming the hole to a given size, the thread is cut with a tap of the proper size and pitch, or it is chased in the lathe. After threading, the cutter should be screwed on to a threaded arbor. Fig. 230 shows an arbor of this description. The end A is threaded slightly taper-

Fig. 230. Typical Threaded Arbor ing, for short cutters about .002 inch in one inch of length. On the taper end of the arbor, a thread should be cut of a size that will not allow the cutter to screw on the arbor quite the entire length; that is, the cutter should overhang the threaded portion' of the arbor a 

larly valuable when mak-ing but one or two pieces of a kind for experimental work, and when making and duplicating screw-machine and similar tools of irregular shape. As these cutters have but one cutting edge, they produce work very accurate as to shape, but they cut very slowly and do not last so long as those having more teeth. However, they are used on special work, on account of the small cost of making. It is necessary to hold the cutters in a fly-cutter arbor, Fig. 231. The cutter to be used in a fly cutter arbor may be filed to a templet, giving the necessary amount of clearance in order that the back edge, or "heel", may not drag. If it is desirable to make the impression in the fly cutter with a milling cutter of the regular form, the piece of square steel from which the cutter is to be made may be held in the mill ing machine vise, and the shape cut with the milling cutter. The desired amount of clearance may be given by holding the piece in the vise at an angle of a few degrees. To make a fly cutter from the forming tool, the piece of steel may be held in the fly cutter arbor in such a position that the face is somewhat back of a radial line, as shown in Fig. 232. After hardening, the cutter should be set so that the cutting edge will be radial, and the clearance will be as shown in Fig. 233. 


Fig. 231. Fly-Cutter Arbor 

>

   pg-152 TOOL-MAKING 
Another method of getting the clearance for the cutter is to place, the top of the cutter blank as near the arbor as possible, and then to', cut the desired shape. If the cutter is set in the arbor so that it 


Fig. 232, First Step Fig. 233. Fly Cutter in Making Fly Set Radial with Cutter Clearance Provided 

Fig. 231. Simple Method of Getting Clearance on Fly Cutter 
projects from the surface, it will have the necessary clearance, as shown in Fig. 234. A represents the position of the blank while being cut, and B the cutter in position for cutting; as the dotted line shows the circle through which the cutting edge travels, the amount of clearance is apparent. End Mills. This form of milling machine cutter, Fig. 235, is familiarly known as a shank mill, on account of the shank, which in small milling cutters fits into a collet. This collet in turn fits the hole in the spindle of the milling machine; the collet is used to save stock in making the cutters, as otherwise it would be necessary to use steel large enough to make a shank the size of the hole in the spindle of the milling machine. The cutter shown in the figure is what is termed a left-hand mill; if the teeth run in the opposite direction, it is called a right-hand mill. In making a shank, or end mill, of the form shown, stock should be selected enough larger than the cutting end to allow of turning 

Fig. 235. Straight Flute Left-Hand End Mill Courtesy of Becker Milling Machine Company, Hyde Park, Massachusetts off the decarbonized surface of the steel. After the ends have been faced to length, and the roughing chip turned, the cutting end can be run in the steady rest of the lathe, and the center cut away, or 


  pg-153 TOOL-MAKING 
recessed, as shown at the end of the mill. The blank should be re-centered and countersunk, to furnish a center to use in turning the mill to size and shape. The object in cutting the center out as shown is to furnish a cavity for the angular cutter used in cutting the teeth on the end of the mill. Without the recess, it would be impossible to grind satisfactorily. After re-centering the recessed end, the opposite end should be turned to size and milled to thickness, which should be a trifle-11,2 inch—less than the width of the center key slot in the collet. The taper shank should be turned enough larger than finish size to allow for grinding after the milling cutter is hardened ; the cutter end should be turned .010 inch larger than the required diameter ; the portion just back of the cutters should be turned 1-2- inch smaller than 

Fig. 236. Cutter with Weak Teeth 

Fig. 237. Cutter with Well-Formed Teeth 

Fig. 238. Cutter with Especially Strong Teeth 

Fig. 239. Method of Cutting Strong Teeth 
the large end of the shank, or to dimensions, if any are given on the drawings. In order to insure teeth strong enough to resist the strain of cutting, an angular mill should be selected that will give the required shape. In Fig. 236 is shown a form of cutter tooth too weak for actual service, the result of using an angular cutter with a cutting face forming an angle that is too acute with the side. Fig. 237 illus-trates a cutter whose teeth are strong, yet deep enough to be practical; these teeth were cut with an angular mill of smaller angle. Fig. 238 represents a cutter whose teeth were cut with the same cutter used for Fig. 236. The teeth were cut to the required depth first, but this of course left them too thick at the cutting edges A, Fig. 239, and the index head was turned sufficiently to cut the teeth as shown at A, Fig. 238. After the teeth around the circumference of the mill have been cut, the mill should be placed in the collet, and the collet put in the spindle hole in the spiral head to cut the teeth on the end. When 


Fig. 231. Fly-Cutter Arbor 

here 3-19-24

/images-American-School-Tool-Making-book/Tool-Making-p-138-139-grinding-an-angular-cutter.jpeg

alt="https://antiquema

  

))))))))))))))))))))))))) 1 new jade green))))))))))))))))))))))))))))
alt="https://antiquemachinery.com/images-American-Machinist-
pg 156 TOOL-MAKING test
grinders are provided with shank while grinding these a fixture for holding the mill by the teeth, Fig. 246. Face Milling Cutters. This form of cutter is used in milling surfaces too large to be cut with the ordinary form of milling cut-ter held on an arbor passing over the work. As the full diameter of the face of the cutter can be used, it can have less than one-half the size that would be necessary for a side milling cutter. A side milling cutter must be double the diameter of the sur-face to be cut, plus the diameter of the collar on the arbor. For instance, if a surface as A, Fig. 247, were to be milled, it would be necessary to use a cutter somewhat larger in diameter than twice the height of the surface plus the diameter of collar B; whereas, if a face milling cutter of the form shown in Fig. 248 were used, the diameter need not be much greater than the height of the face of the piece of work being milled. Generally speaking, cut-ters of this description are necessarily of a diameter that makes it advisable to use inserted teeth. The body may be made of cast iron, having a taper hole and key- Fig. 245. Section of T-Slot Cutter Fig. 246. Grinding Attachment for Shank Cutters Courtesy of Norton Grinding Company, Worcester, Massachusetts Work C Fig. 247. Side Milling Cutter on End Work TOOL-MAKING TABLE VIII Dimensions of Face Milling Cutters DIAMETER OF WIDTH OF TAPER OF HOLE CUTTER FACE (Brown & Sharpe Taper) (in.) (in.) (No.) c,* mloo C,INC9C,IN 10 12 4.1c 12 12 12 way, and held in place on the arbor by a screw. The teeth should be made of tool steel and hardened, or of high-speed steel, if the cutter is to be subjected to rough usage. In either case, they can be fitted to the slots by grinding on a surface grinder, and held in place by taper bushings and screws, as explained under "Milling Cutters with Inserted Teeth". The construction of the body from the sectional view given in Fig. 249. represent diameter of cutter, width of face, and number of taper of the hole, respec-tively, while D represents the keyway. Table VIII gives the dimensions of face milling cutters of different diameters. After the taper hole has been bored and reamed, the body of the cutter should be placed on a taper mandrel fitting the hole, and the ends and cir-cumference finished to size. It is then put in the vise on the shaper or planer at the proper angle, and the spline slot cut to an equal depth at each end of the taper hole. The burrs having been removed, the cutter should be placed be milling machine, and the slots cut for the pg 157
Fig. 248. Face Milling Cutter can be readily understood The letters A, B, and C 14-13-61 Fig. 249. Body of Face Mill inbetween teeth. The centers on the
test 28 pitch
TOOL-MAKING   Fig. 246. Grinding Attachment for Shank Cutters.
Courtesy of Norton Grinding Company, Worcester, Massachusetts.
 
TOOL-MAKING   Fig. 246. Grinding Attachment for Shank Cutters.
Courtesy of Norton Grinding Company, Worcester, Massachusetts
 
gaplllkkghtmi