The bushings job

"Bushing" is a hollow cylinder, more commonly of brass or "bronze" but often of steel and sometimes of tool-steel. The diameter may vary from, say, 3 1/2 inch inside and h/% inch outside, up to say 2 1/2 inches inside and 2% or more, outside. The length is commonly short, from one to three times the outside diameter, and often one end has a low flange.

The bush form-requirements are a truly cylindrical bore, "round and straight" in shop language, with the exterior surface exactly concentric, or "true" with the bore. The bushing is thus seen to be a simple form of production, very easily made on the engine lathe or on the turret machine when made in small quantities and with no special attention to low cost; but when bushings are required in large numbers and at a low cost they offer an extremely difficult problem, or rather several difficult problems, which the Ford engineers have solved by abandoning ordinary machine-tool practice, abandoning the turret machine and the use of reamers for finishing the bush-bore, and making several new inventions in the way of engine-lathe tools and appliances and applying multi-toothed broaches to the finishing of interior circular surfaces, in the effort to produce large numbers of components at the least possible labor-cost.

The Ford Model-T chassis requires 69 bushings, of which 30 are of gray iron, steel or babbitt metal, leaving 39 brass bushings to be made for each chassis; that is to say, with a production of 1,000 cars per day the bushings department regularly finishes about 35,000 or 40,000 bushings daily, and has turned out 52,000 bushings in one 8-hour day.

Up to about April 1, 1913, the bushings were made according to ordinary machine-shop practice, on turret machines, automatic screw machines, and drill presses and engine lathes; many bushes were made from solid round bars on hand-worked turret machines, or of castings.

If of castings, these were bored and reamed on vertical-spindle machines, the bush being held in a special fixture and first rough-bored and then finish reamed, then pressed on arbors and finished to outside diameter and to length in engine lathes.

The management was well aware that the great number of bushings made every day, somewhere about 35,000, cost much more than they should; but up to about April 1, 1913, other things were of more importance and it was not until that time that the bushings production was all collected, placed under the care of one man, and made a separate department.

The first practice followed shop traditions—bored and reamed the bushings holes on turret machines, then forced the bushings onto arbors and turned them, and squared up the ends on engine lathes, placing one man with an arbor press between each pair of engine lathes to force rough bushes on arbors ready for lathe work and force finished bushings off the arbors; one arbor-press hand can keep two lathe hands going.

The first operation attacked was the reaming of the bushholes , which gave no trouble when only a few bushings were required, and the labor cost was not seriously considered.

All kinds and sorts of reamers were tried, but solid reamers held their size only a short time, while adjustable reamers were found not to answer when production was speeded up. Finally circular broaches were given a trial, and have held their own up to the date of this writing.

Three jaws, spring opened, actuated by beam, shown at right, and ring carrying 3 cams. The cams are hardened and the low ends of the levers take adjusting screws with hardened ends, check-nut retained, which gives an independent adjustment for each of the 3 chuck-jaws, making these chucks easy to keep true, year in and year out, holding pieces of the one constant diameter.

Finishing Round Holes with Circular Broaches

The circular broach was in use for round-hole finishing in some Detroit brass shops, though I never saw this tool before I saw it in the Ford Shops, February, 1914. The circular broach is used in power presses, is extremely rapid in action, is easily kept up to size, and makes holes which are nearly circular and beautifully smooth, but are not straight, and never can be exactly straight because the least variations in hardness of the bush sides or in the sharpness of the broach sides must infallibly deflect the broach from straight-line movement as it is forced through the bushing. The bushings-axis variation from a straight line may be as much as two or three thousandths, or as little as one-half a thousandth, but the axis is never quite straight when the hole is finished by circular broaching.

However, in some forms and dimensions of bushes the arbors used are stiff enough to straighten the bush-axis almost perfectly in course of forcing on the arbor and exterior finishing. The axis error limit is fixed at one-half of one thousandth—not too small a limit, since the bushing is the seat of wear, and bushing errors mean working errors, if the bushing seats are straight holes and are correctly located.

The circular broaches have the one grand qualification of working faster than any other tool employed for round-hole finishing, and it is this rapid-action-characteristic which enables the circular broach to hold its place in the Ford shops.

Having found that the circular broach would finish round holes more rapidly than any other tool, the Ford engineers went at the circular-broach construction tooth and nail, and spared nothing in the way of thought, time, and treasure to make the circular broach do its very best.

The longer the broach, with fixed tooth numbers, and the more widely the teeth are separated, the less the power required, the less bursting stress on the work, and the less the closing of the hold after the broach passes through. Also, the longer the broach the more liable it becomes to accident in tempering, in straightening, in use and handling, the longer the stroke must be and the longer the time required.

Late Ford practice favors short broaches. One man and one press broach 2,500 to 3,000 holes, about 2 1/2 inches long, in 8 hours, bronze castings, When broaching with a power press, the length of hole makes little difference in the number of pieces per hour.

Five working-drawings examples of Ford circular-broach practice are given on pages 290 to 293—one of the largest, one of the smallest diameter, and three of intermediate diameters. The circular broaches are not used for any roughing cuts on the bushings job. Circular broaches as small as 5/i6-inch diameter have been in extended use in these shops, but nothing much below Vs-inch diameter is now employed.

Finishes about 100 holes in one grinding. One man and press broach about 3,000 pieces per 8-hour day Brass tube stock, requires very sharp edges. Circular broaches are very quickly ground, either on centers, or by simply holding the broach in the fingers and turning the broach as grinding proceeds. The broach sharpening emery wheels used are the "Norton Elastic," thin disks, round {ace, and flexible, can be readily bent with the fingers and return to flat form when released. The Ford Company circular-broach practice probably includes more experiment that that of any other establishment, and the fact that the Ford Company, after years of use, has settled on the circular-broach employment, is conclusive proof of the advantages of this rapid working tool for certain classes of round-hole finishing, and fully warrants the placing of the illustrations here given.

Probably all circular broaches should have the teeth cut across at as many as three points, 120 degrees apart, in each circular tooth, these cross-cuts being staggered 30 degrees in each successive tooth. Some of the Ford circular-broach teeth are not so cut, with the consequence of making full-circle chips which are difficult of removal from the broachgrooves.

The circular-broach teeth are smallest in diameter at the entering end, and the last three or four teeth are made the same large diameter, often in excess of the finished-hole diameter, as the outward pressure in circular broaching is severe, and the broached hole closes after the broach passes through the thin-walled bushing.

Used for connecting crank-wrist ends. With "gun-reamers," old practice, about 20 rod-ends were reamed per hour, with one man and one drill press; this method required one tool setter on the job constantly; only building 50 cars per day, at time of this single-tooth reamer practice. At present about 4,500 rodends are broached in 8 hours.

The largest and smallest tooth are joined by a curved line of tooth diameters, not by a straight line, so that the chips are thinnest next the broach-leaving end, and thickest at the broach-entering end, as will be seen by reference to the drawings which give the diameter of each circular tooth.

The "Zenith" high-speed tool steel, made by the Carpenter Steel Company at Reading, Pa., is used for these broaches, and for cutting tools generally in the Ford shops.

For broaching holes having key-ways cut in them to finished diameter , a 45-degree angle tool is seated in a mortice at the entering end of the broach to chamfer the key-way inside corners, to avoid turning line burrs inside the key-ways which would have to be removed by hand with a file.

The circular broaches are sharpened by grinding the leading faces of the circular teeth, which are cylindrical for about 1/16 inch in length.

The first or roughing cuts in the bushings holes are made on Cincinnati drillers, with Ford chucks fixed to the driller tables to hold the rough bushes and boring bars; twist drills, soap and water lubricated, are used for making the smaller roughing cuts, which are usually very nearly straight.

The bushings production will be illustrated and described in finishingoperation sequence. The bushing "Ford bronze" castings are now made in the big Ford foundry, and are brought to the bushings department cleaned and ready for the finishing operations.

This elaborate broach finishes the diameter of a hole previously splined to take two keys, 180 degrees apart. The previous splining necessitates the pilot, lower left hand, to guide the chamfering tool, lower right-hand action. In assembling this 4-component tool, the pilot leads, the chamfering tool follows, and both are retained by the thrust screw. In operation, the broach is first entered in the work, by hand, then the job is placed in the press and the broach is forced through.

    The finishing operations, considered in their regular order, are as follows:
  • Operation 1. Rough Bore, Ford chuck.
  • Operation 2. Broach, broach grinding included.
  • Operation 3. Place on arbor, or otherwise hold for turning, and force off arbor.
  • Operation 4. Turn, square ends, or cut in two.

Finally, The forming of bushes from flat strips of metal in power press, cut off and form one bush at each down stroke of the press slide, will be shown and described.

Rough-Boring Bronze Bushes

The tools used are 21-inch Cincinnati drillers, fitted with Ford universal three-jawed chuck, shown on page 289. See caption for chuck construction. The chucks are fixed to the driller tables, concentric with the driller spindles. See the illustration on page 288.

The preferred boring tool is a boring bar, with a screw-retained, double-end cutter, the bottom end of the bar being steadied in a hardened and ground bush seated in the chuck-body. For small-diameter holes rough boring is done with twist drills. The lubrication is flooded soap and water, circulated by a two-pinion pump.

For large-diameter bushings the cutter is ground about once for every 100 bushings rough-bored. The broach seen standing on its end at the right side of the driller table, Figure 15, is used for the roughbore gauge. About 900 bushes of the largest diameter, something over 234 inches, are bored per 8-hour day. Small bushes are rough-bored with a twist drill, 1,800 per day, one man and one machine, 8 hours.

A special machine for bushings boring is now under construction, and is expected to reduce the labor cost of bushings boring very much.

The Ford special three-jaw chuck is shown on page 289 and described in the caption. These chucks are simple, hold strongly, are extremely durable, and have an independent screw and check-nut adjustment for positioning each chuck jaw.

Broaching Bore to Finished Diameter

Although the Ford shops had a circular broach in successful use for some years, finishing the connecting-rod wrist-eyes, in babbitt metal (and was having plenty of trouble in finish-boring the bushes) no bush bores were broached before about April 1, 1913. It is difficult to work babbitt without tearing the soft surface, and babbitt-cutting tools must have keen edges to produce smooth work. This keen edge requirement for babbitt broaching discouraged the Ford engineers in the matter of sizing bronze bush holes with circular broaches, possibly. At all events, broaches were not tried on the bushings until after everything else had been tried for the job, with no satisfaction. Broached holes in brass are invariably smooth, but sometimes spring to oval form where the broach drops through and are never exactly straight; sometimes

to within half a thousandth of straight and sometimes as much as two or three thousandths out of straight. Speaking generally, the circular broached holes may be said to be round and smooth, but not straight.

The action of the broach is extremely rapid, and broached surfaces in brass are smooth; the great use of the circular broach in the Ford shops is enough to warrant a trial of broaching by any shop which wants to finish holes up to 2 1/2 inches diameter, in brass, in large numbers and at low cost.

Broaching Bushes

The broaching is done on geared Ferracute presses, "D. G.—54," 8 inches stroke, one man only to each press. Operations are: pick up bushing with left hand; pick broach out of tray under press bolster, with right hand; enter broach in bushing, both hands; hold bushing in place under press slide with right hand; depress clutch treadle with right foot (the broach shank is made long enough to carry broach teeth all the way through the work, so that the broach drops down into the pan); finally, with right hand, place broached piece in tray.

By using two men on a press, one helper to pick up the bush and enter the broach, the press output can be increased, but the one-man work cannot be doubled. The least 8-hour number, large holes, is about 2,500 pieces broached.

Sixteen holes broached per minute is about top speed. Regular production of medium-size work, 4,000 bushes broached in 8 hours, with one man and press.

Broach Grinding

With difficult stock the broach may have to be ground once in half an hour. With the best stock the broach may hold up to size for 8 hours. Regular practice is once in 5 hours.

From 12 to 24 broaches of each size used are kept on hand in the tool crib.

Breaking of small broaches is rare, and is caused by uneven seating of the bush on the press-bolster. The large broaches never break. Broach grinding is rapid. The broach is not placed on centers, but is held in both hands up to an "Elastic" Norton wheel, 7/16 to 7s inch thickness and 6 or 8 inches diameter, and it takes Only tWO or three minutes to snarpen any broach.

Forcing Arbors Into and Out of the Bushings

The hand-worked arbor-press, first used for forcing arbors into and out of bushings, is not so fast as press work for the same operation, shown on pages 297 and 298. The former view shows the press man holding a finish-turned bush on its arbor upright with his left hand, and an un-turned bushing with arbor entered upright in his right hand on the press bolster, under the press-slide. When the press-slide comes down the arbor is forced out of the left-hand bush at the same time that the arbor is forced into the bush held in the workman's right hand. The forced-out arbor drops into the trough, S, page 298, and the press man drops the finish-turned bush into the slide at his left, page 297, at the same time that he drops the bush and arbor held in his right hand on a sttde, not seen, leading to the lathe lines in rear of the press. The press man has a helper standing at his right, shown idle in this posed picture, who picks the arbor out of the trough, S, page 298, and enters it in another bush. The press hand takes the un-turned bush with its entered arbor in his right hand, and with his left hand picks up a finish-turned bush on its arbor and completes the cycle of his movements by standing both assemblies on the press-bolster, as shown on page 297, ready to repeat.

Two men and one press handle about 16,000 bushings and arbors in 8 hours, place 8,000 bushings on arbors and push the arbors out of 8,000 bushings.

One man collects the turned bushings on arbors from the lathe lines and places them in the tray at the extreme left in the view on page 297.

Page 298 shows a detail view of the press-bolster and slide. At left front, on the bolster, is a turned bushing on the arbor, arbor flattened end for lathe-driving in front. At middle left, in a raised boss on the bolster, stands a bushing ready to have its arbor forced out; immediately above, down-hanging from the press-slide fixture, is the round driver, marked "A," of smaller diameter than the arbor, which forces the arbor down all the way out of the bushing. To the right of "A" is the short plug "B," which drives the arbor into the bush, standing on the bolster at right middle. At right front, a bush, with an arbor entered ready for driving in, lies in the bolster.

Turning the Bushings

See page 299, double line of bushing-turning lathes, by Reed-Prentice Co. Extreme left, man at rack and pinion arbor press, old style, who can handle from 900 to 2,000 bushes on and off the arbor, both operations , in 8 hours, according to the length of the bushings. With the power press the length of the bushings does not count, long bushings being handled on and off the arbor as rapidly as short ones.

Driving and Turning Bushes

The arbor presses are seen at right middle distance. It shows the lathe ready to take an arbor with bushing on it ready for rough- or finish-turning. Bushings ends are not faced in this operation.

Lathe Centers

The live center is fitted to slide to a shoulder in the headstock spindle, and is pressed outward by a light spring. The tail-center has a taper socket fit, usual style, in the tail spindle, which has no tail-screw, the tail-spindle being forced forward by a spring heavy enough to close the live-spindle-center coiled spring; tail spindle has usual clamping screw.

The live spindle is fitted with a floating driver to take and drive the flattened arbor end, and a stud fixed to the lathe carriage impinges the tail spindle front end, below the center, so that the tail spindle can be forced back against the spring pressure by turning the lathe-saddle hand-wheel. This CUt shows 20-tOOth circular turning tools used for bush-turning, and these peculiar tools are also shown on page 302. These multi-tool cutters are believed to have originated with the Ford engineers. The first one used was taken from a Fellows gearshaper ; afterward these tools were tried in cylindrical form with both straight and spiral teeth, but have now become standard, on the Ford bushings job, in the form shown on page 300, a truncated cone, 2 inches outside diameter, holes J^, thickness J;g, 20 teeth, taper about 10 degrees on a side, 20 degrees included angle, with 30-tooth V-form retaining ratchet on bottom end. The teeth are round-nose for roughing and flat-nose for finishing. The finish tools are set to clear on the following side. As there are 20 cutting teeth and the holder retaining ratchet has 30 teeth, the cutter holder is fitted with a retention screw adjustment which must be varied when a change is made from one cutting edge to the next one. These cutters are ground on top at the big end, and one grinding gives 20 sharp tools in one piece. The cutters have milled elevating hand nuts on screws under them.

Turning Bushes Operation

The live spindle runs continuously. With the lathe as shown in cut on page 302, the live center is forced outward by its light spring.

The lathe man takes hold of the lathe-carriage wheel with his left hand, pushes the tail spindle back with stud on lathe tool-post fixture, takes arbor with bush on it in his right hand, applies the flat driving end of arbor to live center, guides the arbor tail end and lets the tail spindle spring force the live center to shoulder, the arbor flat entering the floating live-spindle driver, tightens the tail-spindle clamping screw, and proceeds at once to run the cut over the bush with hand-wheel carriage feed. As soon as the cut is over, the workman picks up another arbor with bush on it in his right hand, then releases tail-spindle clamping screw with right hand, then moves right hand to bushing and arbor on centers and pulls the top of hand wheel towards him, pushes the tailspindle back, drops the unturned bushing and arbor down on his fingers, and grasps the turned bushing with thumb and forefinger of right hand, lifts right hand enough to put fresh job on centers, moves hand wheel enough to let tail center go forward and push the arbor flat end into the driver, tightens the tail-spindle clamping screw with right hand, and then drops the finished bush and arbor into the trough; as soon as the tail spindle is clamped the workman starts the cut with the hand wheel and picks up the next job with his right hand about the time the short cut is made, and so on. The workman's left hand does not leave the hand wheel and the live spindle is not stopped. Each workman turns about 2,000 bushes per 8-hour day. One lathe makes the rough cuts and another lathe makes the finishing cuts. Two helpers place the arbors and bushes conveniently for the lathe men, and from the finish lathe the arbors and bushes go to the "put-on" and "take-off" power press, as shown on pages 297 and 298. The operations are performed so rapidly that it is difficult to follow the varied performances of the man's right hand.

An arbor with bush on it, ready to turn, lies on top of the tail stock in front of clamping screw. One toolholder , with 20-tooth circular cutter, is shown in working position, and another tool post is set on the lathe carriage, middle front of picture, to show the tool-post construction and the 20-tooth circular cutter.

It will be noted that the latheman has a bush and arbor in his right hand both when releasing and when tightening the tail-stock clamping screw with that hand, and also that he has a bushing and arbor in his right hand when he takes a bushing and arbor off the lathe centers, and that he drops the fresh bushing and arbor down on his right hand second and third fingers so that he can grasp the turned bushing and its arbor with his right hand thumb and fore-finger while he lifts and places the fresh job on the lathe centers, all of which seems very awkward, but is really a great saving of time and hand-travel distance over ordinary practice which would handle both the two arbors and bushes with the right hand.

These turning lathes do not square up the bush ends. Some of the bushes are made two in one piece and are cut apart and have ends squared to length by subsequent operations on expanding arbors.

The bushings department has a line of eight new special Reed-Prentice lathes, which are expected to change the entire routine of bush finishing; expanding arbors are now being made, and practice is not fully determined. No illustrations are given of this new line of lathes.

Bush-Forming Dies

On pages 303, 304 and 305 appear views of a bush-forming die, which cuts off lengths from flat strip stock, steel or brass, and forms up a complete bush at each down stroke of the slide of a single-acting power press. Formerly many bushes were made by cutting lengths from steel or brass tubes.

The flat strip is fed by hand, between side gauges, to a stop. The punch descends, first cutting the blank to length, and then continuing to move downward forms the blank U-shape, at the end of the punch down-stroke. The punch then rises, and the ejector, spring-forced outward, is released by rising of the wedge fixed to the punch and pushes the U-blank outward so that it hangs on the "coaxing" arbor; see section of punch and die, open and closed, on page 303.

An inverted U-form bushings blank is seen in front of stock-strip, hanging on the "coaxing arbor," see page 303. Note three stages of bushings lying and standing on the press bolster.

Next the strip is fed as before, and the descent of the punch cuts off a second blank and forms it in a second U-blank, at the same time forcing the first U-blank hanging on the coaxing arbor downward, the inverted U-ends striking the die semicircle, and forming the first U-blank into a cylinder, which is ejected when the punch next rises.

The coaxing arbor and the U-block are integral, and are set on a lifting spring retained by a down-hanging shoulder screw, so that the coaxing arbor and U-block can go down together and be returned together as the punch rises, until stopped by the underneath shoulder screw.

When the punch rises the second time the ejector pushes the second XJ-blank outward, which forces the completely formed bush off from the coaxing arbor, thus making room on the coaxing arbor for the second U-blank.

Springs and Spring Plungers

The shearing blade is fixed to the punch body, and is cut in the middle of its under side to a half circle, to form the top of the inverted U-bend. A spring plunger is fitted in the middle of the half circle, which acts as an ejector when the punch begins to rise, to force the inverted U-blank to lie down close on the U-block.

Operation

See "PunchUp," in the illustration on page 303. In descending , the punch wedge moves the ejector to the right, so that the ejector-fork ends at the left barely clear the blank as the punch forces the blank downward after shearing the blank from the flat strip stock, and forms the blank to inverted U-shape at the same time (save in starting stroke) forming the inverted U-shape to a perfect cylinder around the coaxing arbor.

When the punch begins to rise the small spring plunger marked "S," in "punch down," holds the inverted U-blank on the "U-block" up to the time when the "ejector" begins to move the inverted U-blank to the left, pushing the completely formed bush off the coaxing arbor to give the U-blank place on the coaxing arbor.

This bush-forming die is given space because it is new, and can make 62 bushes per minute, completely formed, and hence may be of use to the trade at large.

The stroke of the press slide is 3 1/2 inches; similar dies make bushings from diameters 9/16 and 11/16 by 1 1/2 inches long to diameters 3/4 and 1 inch by l 1/4 inches long.

In April, 1913, 984 hours were required to equal present production of bushes. Now (October, 1914) the bushings department performs this work in 480 labor hours, at about one-half the cost.

What the cost will be when the press-formed bushings are placed wherever they will answer, and when the eight new lathes are working up to expectation, is a subject for conjecture only, but may, possibly, split the present cost in half.