The Iron Age 1924-03-27: Vol 113 Iss 13

WS New York, March 27, 1924 ESTABLISHED 1855 VOL. 113, No. 13 From Blast Furnace to Malleable Casting Malleable Foundry at Cadillac Adjoins Charcoal Furnace Suspended Molding Machines, Annealing Ovens, and Buggies for Material Handling Are Features BY GILBERT L. LACHER Y bridging the gaps in production from raw ma- terial to finished commodity notable economies have been achieved in American industry. Among outstanding examples, the large integrated steel companies have developed plants in which the metal passes from blast furnace through open-hearth furnace and blooming mill and to finishing mill in un- interrupted progression. Conservation of heat, of course, is one of the important advantages derived from such a unification of the steps in manufacture. Molten iron no sooner passes from the tap hole of the blast furnace into the ladle than it is transferred to a large pig iron mixer, whence it is poured into the open-hearth furnace. After the steel is made, it is cast into ingots, which are stripped of their molds as quickly as the metal solidifies and deposited in soak- ing pits prior to rolling. These evident economies no doubt inspired a leading motor car builder to apply the same principle to gray iron foundry practice, pouring the hot iron tapped from his blast furnaces directly into his cupolas. The prospective adoption of this idea in connection with the air furnace was one of the reasons which led to the construction of a foundry at Cadillac, Mich., by the Cadillac Malleable Iron Co. This plant was built immediately adjacent to the charcoal iron blast furnace of the Mitchell-Diggins Iron Co. and the operation of the two works, although under separate managements, have been closely coordinated. Although the use of molten pig iron in the air fur- nace is not yet practicable, because the foundry’s con- sumption is still insufficient to warrant the taking of daily blast furnace heats of the analysis required in the malleable plant, other advantages of more imme- diate significance have been gained from the location. In the first place, it was desired to use charcoal pig Air-Operated Squeezer Machines Suspended From Monorails Are Used for All Molding Work. There are 31 molding floors, each equipped with a machine. The floors are narrow and long, 10 x 45 ft. each, so that molders can work at one end on cold sand while molds are being shaken out and sand is being cut over and tempered at the other. At top of page, the building with the Pond-type roof houses the foundry, while the annealing building is at the left. At right is the blast furnace plant of the Mitchell-Diggins Iron Co. 921 iron exclusively and this is insured by close proximity to the source of production. Likewise, economies in power, lighting and heating were made _ possible through the utilization of waste energy from the blast ot furnace plant. Finally, Cadillac is admirably situated . for the production of castings for the automotive in- dustry. While proximity to a blast furnace is an unusual feature, it is by no means the only claim of the plant on the attention of the visitor. The layout is unusu- ally well planned to permit future expansion. Molding equipment is admirably adapted for rapid production. THE IRON AGE March 27, 1924 ber of modifications from the design of its prototype Through an adjustable goose-neck supporting column connecting the machine with the overhead tro) ley, the center of gravity is thrown directly under the trolley, so that ease of movement along the rail assured. The core bench is now held rigidly from body of the machine and has no supporting whee! resting on the floor. It was found that the wheel. ; following the irregularities of the floor, would jar bench and damage the cores. Another advantage accruing from the omission of the supporting wheel lies in the fact that it permits The expeditious and direct conveyance of materials is the molder to pile bottom boards in a row alongside ae. aaa SSF,” es” ~~ Pe : 7 LOADING D : ATFo, : - : TORACS ‘ WGA DOCK , [zo PL ’ N a A N - y B® jet game | 2 : LABORATORY OFFICE 7. be biaitiionas "1 Lp ~ | eee ((]GARAGE —_ ~ STOCK ROOM F ae) n ue SHED ) CM SHtD STORE ROOM | te ge aes “| FSAND BINS : 1 FUTURE CORE ROOM : roe PE es ee en ' r 1 i | FUTURE } ; | | ADMINISTRATION ; ! _1 "BUILDING; IPROPOSED PROPOSED | FOUNDRY BUILDINGS} | | { ' j | | \ onan BUILDING : | \ | OE APROPOSED CONNECTIN | \ > PASSAGE PASSAGE mt ; piece ale ema | amare r= | ! ' | \ ' / 1 | 1 ty iss sie catceind hace MBLING Mil vf eee ED| TF 1 PATTERN | 9 50 ISHOP AND y | STORAGE | This Plan of the insured by the layout of the plant and the handling equipment provided. The annealing department is noteworthy for its arrangement and for the late de- velopments in design embraced in the annealing ovens. Pneumatic Molding Machines Air-operated squeezer machines suspended from monorails are used for all molding work in the foun- dry. There are 31 molding floors in all, each equipped with a machine. The floors are narrow and long, measuring 10x45 ft. each, so that the molders can work at one end on cold sand while molds are being shaken out and the sand is being cut over and tem- pered at the other. This arrangement is essential in a malleable shop where two heats are taken daily. The molding machines, suspended from monorails, are 4 of the Teetor type and were developed from the Howe suspended molding machine, which was described for the first time in THE IRON AGE of March 4, 1920, page 665. The Teetor machine, however, embraces a num- ; id : eae e Cadillac Plant Shows Its Proximity to the out of Future PROPOSED ANNEALING BUILDING Charcoal Blast Furnace (at Top) and the Proposed Lay- Extensions his molding sand and directly under the course of the suspended bench. The legs of the present machine, unlike the original, may be folded up, so that molds and heaped sand on the molding floor may be cleared at will, permitting the molder to transfer his working position to any part of the floor that suits his con- venience. A sand riddle has been attached to the side of the machine opposite the core bench, further to eliminate unnecessary motions on the part of the molder. The riddle, pivoted on an arm, may be swung out of the way when not in use. The air-operated squeezer and the air-adjustable legs with broad supporting feet are substantially the same in design as in the first machine. The adjust- able feature of the goose-neck support is particularly noteworthy, because it permits the machine to be turned completely around, if: it is desired to reverse the direction of molding work, and also makes possible correction of the center of gravity. This is — ally necessary when the bench is piled with heavy March 27, 1924 As the Legs of the Molding Machine May Be Folded Up, Molds and Heap Sand May Be Cleared at Will, Permitting the Molder to Transfer His Work ing Position to Any Part of the Floor that Suits His Convenience Through the goose neck supporting column the center of gravity of the machine is thrown directly under the trolley, in- suring ease of move- ment along the rail cores which throw the center of gravity out of position under the trolley. Adjustment of the goose-neck is pos- sible through collars and set screws at top and bottom. Now the question arises as to what results are achieved with suspended machines employed in pro- duction work. Castings made from the machine-made molds range from the smallest up to 30 lb. each. In February, 1924, the average daily output of good castings per molder was 766 lb. This record is even more impressive when it is borne in mind that the foundry had to train its own molders. Cadillac is primarily a lumber and furniture center and in metal working, outside of the malleable plant, contains only a small gray iron foundry. The progress which has been made in the face of this condition commands at- tention. In December, 1922, the first month of opera- tion, the plant produced 50 tons of castings. In February, 1924, the output was 256 tons. All of the columns in the molding room have elec- For Charging and Handling the Bungs, the Air Furnace Is Commanded by a Floor-Operated Blectric Traveling Overhead THE IRON AGE tric plugs, so that connection may be made by the American Foundry Equipment Co. sand cutter when it is operating over any molding floor. Compressed air lines carry the air required by the molding machines. Air is supplied at 85 lb. per sq. in. pressure by an Ingersoll-Rand 600-cu. ft. two-stage compressor. 15-Ton Air Furnace Located in the middle of the molding room, the air furnace was built by Holcroft & Co., Detroit. At pres- ent it is hand-fired with coal, but the management contemplates the installation of powdered fuel equip- ment. With a rated capacity of 15 tons, it has pro- duced 16 tons, although no particular effort has been made to press it for output. A feature of its con- struction is its large bungs, which are 3 ft. in width, permitting charging with the removal of only three bungs. For charging and for handling the bungs, the Crane a eee oo x 924 THE IRON AGE TTT) bd ae aa ia ch LL < . oe | esc Sohal ce Co < March 27, 1924 These Annealing Ovens Are Believed to Have the Largest Doors in Use, Measuring 20 Ft. Wide by 9 Ft. High at the Center. Through counterweighting, lifting can be handled easily by one workman furnace is commanded by a floor-operated 5-ton Whiting electric traveling overhead crane. Charges of pig iron, sprues and trimmings are accumulated in three-sided rectangular trays suspended by chains. The hook from the chain on the open side is knocked out when the tray is over the furnace and ready to be discharged. Close control of the analysis of the charge is as- sured through a system used for keeping track of the sprues and trimmings, which are returned to the fur- nace. A chemist employed jointly by the blast furnace and the foundry makes an analysis of each heat from the furnace. Ordinarily silicon is the only element which varies to an extent worthy of attention, but if irregularities are observed in the action of the furnace, that is an indication that the carbon will likewise show variance, in which case sprues and scrap from that heat are not returned to the furnace until the carbon analysis, which takes longer than the silicon analysis, is taken. Sprues are accumulated on the molding floors after shaking out, and deposited in buggies to which cards are attached indicating the heat from which they were poured. When this scrap is returned to the furnace, therefore, it is known definitely what the analysis is. Trimmings from the tumbling barrels and sorting tables returned to the furnace are generally mixed, containing metal from both morning and afternoon heats. .-In this case an average is struck between the two analyses. For various reasons it is impracticable to keep the two heats separate in the tumbling depart- ment. For instance, light and heavy castings cannot be tumbled together without danger of breakage. Hence castings of both heats must be suitably sorted, group- ing castings of similar size together. As the tare weight of each buggy is marked on it, the weight of pig iron and scrap is easily ascertainable by placing the buggies on a 6-ton Howe scale located near the air furnace. In one corner of the molding room, at the raw material receiving end of the building, is located the core department. Prominent features of its equipment are a core blowing machine, made by the E. J. Woodi- son Co., Detroit, used for making large body cores; a Simpson No. 1 motor-driven sand mixer, built by the National Engineering Co., Chicago. and a coke-fired Coleman core oven. Besides a main drying chamber, this oven has an emergency chamber entirely separate, with shallow drawers which may be used for the fast drying of small cores. Core sand is dug from shallow pits in the company’s own property, being used direct from pit in summer and from store in the bins in winter. The floor of the foundry is of an entirely new type, consisting of paving brick set on sand and separated by 4-in. joints filled with cement grouting. This makes a smooth, hard floor, but does not have the dangerous fault of a solid concrete floor—of exploding hot metal. The brick is porous and allows the moisture to seep through it, in contrast with the concrete. The gang- ways are of wood block on concrete foundations. The central gangway of the foundry connects with the annealing building, running straight through the entire plant from end to end. A ramp in this gang- way leads to an elevated platform in the anneal- ing department, where castings are discharged by gravity into tumbling barrels. The space underneath the ramp is utilized for storing fire clay, while mis- cellaneous foundry stores are kept under the tumbling mill platform. Tumbling and Grinding There are three motor-driven 36 x 48-in. tumbling barrels, built by the Whiting Corporation, Harvey, Ill. A dust collecting system removes from the mills all except the heavy dust, which drops to concrete bins on the floor underneath. Above and in front of the dust bins are sorting benches to which the castings are discharged after tumbling. Workmen stationec here trim and test the castings with hammers, and then sort them for subsequent grinding. : The grinding equipment, entirely motor-driven, cludes one 24-in. double-end grinder, built by the in- March 27, 1924 Bridgeport Safety Emery Wheel Co., and two double- end 18-in. and two double-end 14-in. grinders, con- structed by the Dillon Electric Co., Canton, Ohio. The 24-in. machine is used for wheels down to 18-in. when transfer is made to the 18-in. machine in order to maintain the high peripheral speed necessary for suc- cessful grinding. The same holds true of successive diameters between 18 and 14-in. Annealing Ovens with Large Doors The annealing ovens are believed to have the largest doors in use, 20 ft. wide and 9 ft. high at the center. In ordinary practice the door is put in place in sec- tions, but here the door is one solid mass, made up of steel framing and “nonpareil” brick, made by the Armstrong Cork Co., Beaver Falls, Pa. In fact, the high heat-resistant qualities of the brick made the construction of a single door possible. The door is coated on the back with a high temperature resistant cement, No. 26, made by the Johns-Manville Co., New York. Arrangements for lifting the door are note- worthy. It is suspended on two chains which are counterweighted, while a third chain from the center of the top of the door. is connected with a hand- operated hoist by which a workman can lower and raise the door with ease. To permit the expansion of the floor of the anneal- ing oven and to insure the return of the floor to its normal position when it contracts, power springs have been placed between the oven floor and the concrete wall of a trench built in front of it. The springs are adjustable by hand screw, so that the proper pressure can be obtained. Similarly, springs have been placed in a trench in back of the oven and springs have been provided on the rear end of the roof, these being at- tached to tie rods extending the length of the oven. The foundations of the ovens, which are separate from those of the building, are unusually heavy. At the base of each oven structure is a concrete slab, 12 in. THE IRON AGE 925 thick, superimposed upon which is a massive founda- tion of fire brick. Inside dimensions of the oven chamber are 20 x 25 ft. and the height from floor level to spring of arch is 9 ft. Each oven has an individual stack, an arrange- ment which is conducive to better heat control. The stack is located in the middle of the back end of the oven, and on each side are fire boxes in which coal is burned. Heat generated in the fire boxes passes up over a bridge into the oven chamber, whence it is drawn down through flues at the base of the two side walls. The wall flues connect with a series of parallel flues running lengthwise underneath the oven floor. The eourse of the circulation, therefore, is from the side walls back and forth lengthwise of the oven toward the middle, whence the gases from both sides are conveyed to the stack. Each oven has two thermocouples, one about two- thirds of the way back on the top, and the other at the bottom of the door, the coolest point in the cham- ber. Temperatures from both points are recorded by a temperature recording Leeds & Northrup potentio- meter—one for each oven. The aim is to keep the temperature at the coolest point at 1500 deg. Fahr. Each of the four ovens has a capacity of approxi- mately 40 tons of castings, or about two days’ output from the foundry. Hence the four ovens, which are operated on a 10-day cycle—somewhat longer than is usual in malleable practice—handle the output of eight working days. The omission of work on Sundays and Saturday half-holidays makes the ovens amply large to handle the production of the plant. The ovens were designed and built by the Cadillac Malleable Iron Co.; the doors were designed by Frank D. Chase, Inc., Chicago. No packing is used in the annealing boxes, the separate containers being insulated from each other through the use of flanged separator plates together with the customary mudding up of all of the joints. Jack-Tongue Buggies Have Been Provided for Handling Material. For hand hauling a jack-tongue wheel is at- tached to the buggy. The jack-tongue is used also for dumping the contents of the buggy. For movement of buggies in train, smaller con- necting tongues join the front bearing of one buggy with a draw-bar in the back of the buggy ahead. Here a train is being driven up a ramp leading to the tumbling mill platform sath wsegnah em j 7 F : be gS EEE — ny Cerne ~ 6. L. = ee 926 THE IRON AGE March 27, 192. After shaking out the annealing boxes, the castings are sorted, some of them being sent to the sand blast and others to the tumbling barrels. The sand blast equipment is located on a platform connected with the annealing room floor by means of a ramp. This per- mits the castings to be discharged into the sand blast machines by gravity and also deposits the finished castings on the floor level, ready for packing and ship- ment. There are two revolving barrel gravity-type positive feed sand blast machines, built by the Ameri- can Foundry Equipment Co., New York. Beyond the sand blast department is the shipping room. A large door allows motor trucks to drive in for loading. Bins have been provided for sorting castings, small castings being bagged, while large ones are shipped loose. The shipping room has a straighten- ing hammer, made by the Canton Foundry & Machine Co., Canton, Ohio. Material handling facilities in the plant are ex- cellent. There are 200 MHowe-Teetor jack-tongue dump buggies, designed and patented by R. J. Teetor, secretary and general manager Cadillac Malleable Iron Co., and the late Eugene L. Howe, formerly president Standard Malleable Iron Co., Muskegon, Mich. This buggy has a body similar to that of a wheelbarrow, being adapted for end dumping, and can be moved by hand or by motor truck in train. It has two permanent wheels in back, and in front has a bearing in which a jack tongue equipped with a single wheel may be inserted for hand hauling. As all wheels run on Hyatt roller bearings, ease of movement is assured. For movement of the buggies in train, smaller con- necting tongues join the front bearing of one buggy with a draw bar in the back of the buggy ahead. Trains are moved either by electric storage battery truck or by gasoline tractor. The former, built by the Elwell-Parker Co., Cleveland, is equipped for charging annealing boxes into the ovens. It is not required for the latter purpose continually, however, and therefore is available for other uses. The gasoline tractor, made by the Clark Equipment Co., Buchanan, Mich., is used also for general service, being equipped with a 24-cu. ft. dump body so that it may be employed to haul sand, fire clay and coal. Electric light and power are obtained from a power plant at the Mitchell-Diggins works, the steam being produced in boilers which burn surplus waste gas from the blast furnace. Similarly, exhaust steam from the power plant is used to heat the foundry. The dynamo produces 440-volt, 60-cycle, 3-phase current, which is used untransformed to operate the traveling crane serving the air furnace. Current is transformed to 220 volts, 60 cycles, single-phase for the operation of the sand cutter and other mechanical equipment. For lighting it is stepped down to 110 volts, 60 cycles, single-phase. Radiators have been placed along the walls of all the buildings comprising the malleable plant. In addi- tion, the foundry has an overhead hot-blast system in which the air is heated by radiators, both the hot- blast system and the radiators supplied by the Ameri- can Radiator Co. Buildings and Extension Plans The foundry building is 120 ft. x 198 ft. and has a Pond-type roof, the peaks of which are 40 ft. above grade. Continuous sash has been provided in the monitors and side walls. Prepared roofing over roof boards covers the structure except over the air furnace, where cement tile, supplied by the Continental Cement Tile Co., Chicago, was used instead of wood. Brick trim has been used on the ends, while the sides are of false construction to permit later expansion. The false walls are made of asbestos wood siding, bolted onto the steel work. Plans provide for the construction of three moldine rooms on one side and four on the other side, ea identical with the present foundry, so that, if co, templated expansion finally eventuates, there wil! eight air furnaces with a total recorded capacity 120 tons. Expansion of the annealing building will take plac. in both directions also. A new battery of ovens w be built opposite the present battery to serve the next foundry addition, and, then subsequent batteries wi! be constructed back to back with those two. In othe words, only four annealing buildings of the present size will be required to take care of eight molding rooms. The annealing building is 90 x 228 ft. and is 35 ft. high from floor to roof, barring the portion which houses the ovens, which is really a leanto adjoining the main structure. The latter has a flat arch roof covered with roof boards and composition roofing. Th« floor is paved with wood block; the side walls. hav: continuous sash. Next to the gangway connecting the annealing building with the foundry is a service and office build- ing, 40 x 67 ft. In the expansion plans, this structure will eventually be used entirely for toilet and locke facilities, and a separate administration building will be built elsewhere. The plant is served by a railroad siding owned jointly by the Ann Arbor and Pennsylvania railroads. Next to the siding are a sand storage building, 24 x 126 ft., and a coal storage yard. A motor-driven con- tinuous conveyor built by the Chicago Automatic Con- veyor Co. and suspended from a trolley rail is used for handling coal and sand in the material yard. The sand storage building is of frame on concrete founda- tions and contains three bins, each having a capacity of four carloads. The bins have high windows for unloading from open cars and doors on the level of box car doors for unloading from closed cars. The sand bins are steam heated in winter. Frank D. Chase, Inc., Chicago, was engineer in charge of the design and supervised the construction of the plant. Fabrication and erection of the steel work was by the Indiana Bridge Co., Muncie, Ind. The Cadillac Malleable Iron Co. was organized June 1, 1922, and the officers include: J. C. Ford, president; C. T. Mitchell, vice-president; R. J. Teetor, secretary and general manager. and G. G. Brown, treasurer. Secretary Hoover’s Reply to Mr. Untermyer WASHINGTON, March 25.—Secretary of Commerce Hoover has made a vigorous reply to charges by Attor- ney Samuel Untermyer, who, in a recent letter to Sen- ator Capper, of Kansas, bitterly assailed Mr. Hoover in connection with recommendations made by the latter to Senator Capper for an amendment to the Webb- Pomerene export act. The proposal of Mr. Hoover which has been acted upon by Mr. Capper, calls for the setting up of common purchasing agencies of America! importers of essential raw materials which are con trolled by foreign monopolies. Mr. Untermyer chargec that Mr. Hoover, while trying to control foreign monop- olies, had protected domestic monopolies. Mr. Hoover, replying to Mr. Untermyer in a lette: to Senator Capper, charged that Mr. Untermyer “'s either engaged in slander or he is losing his memory, or knows nothing of the functions of the Department of Commerce, or he is endeavoring to oppose efforts * restrain foreign price combinations.” Mr. Hoover made the point that the Department 0! Commerce has nothing to do with the law against com- bination in restraint of trade and that if Mr. Unter- myer had any complaint to make it should be ad- dressed to the Federal Trade Commission or to the De- partment of Justice. Close Manufacturing Limits Discussed Practical and Impractical Requirements Cited—Good Practice in Establishing Tolerances—Reasons for Difficulty in Producing Smooth Running Gears ances judiciously was emphatically brought out by B. H. Blood, general manager Pratt & Whitney Co., Hartford, in a paper on “Some Limitations on Manufacturing to Close Limits,” read at the machine tool conference held March 25 under the auspices of the Engineers’ Club of Philadelphia and the Philadelphia section of the American Society of Mechanical Engi- neers with the cooperation of the machine shop division of the American Society of Mechanical Engineers. The ['sxe necessity of specifying manufacturing toler- 4-4 Fig. 1—Dimension Sketch of Steel Cylinder conference was held at the Engineers’ Club, Philadel- phia. The facts brought out by Mr. Blood are summarized in the following: In order to manufacture to close limits, it must be possible to measure to still closer limits. The measuring means should be as direct as possible. Even where direct and accurate means of measur- ing are available, close work is expensive and should be called for only where the expense is justified by the requirements. Tolerances should be set only after a careful study of their necessity and their cost. If right, they should be adhered to. If not, they should be changed. Cumulative tolerances should be avoided. In plac- ing a tolerance figure on a drawing, the draftsman should consider how it can be checked, the obser- vational error of the measuring instrument, and the influences of tolerances on other related dimensions. Dimensions should read from fixed and accessible points. Greater clearances usually permit greater toler- ances. If both can be increased with safety, economy is bound to result, and in many cases the product may be actually improved thereby. Coming as the author does from a shop whose business and reputation have been built on precision manufacturing, this doctrine may sound strange. Dirt has been defined as any matter out of place. How shall we describe precision out of place? In manufacturing to limits the first essential is to be able to measure, not merely to those limits but much more closely. The great majority of manufacturing operations in metal consist in removing surplus stock. To hold to any specified limits it is only necessary to stop at the right point. Our means of measuring must show us how closely we are approaching that point, and warn us before we pass it. Thirty years ago very few machinists had ever seen a micrometer. Close dimensions were expressed on drawings in sixty-fourths of an inch. A drawing with sizes and tolerances expressed in thousandths would not have been intelligible. Yet the skilled mechanic worked in thousandths without knowing it. He would produce a drive fit, a sucking fit, or a running fit that was en- tirely serviceable, if he had the nicety of touch and the patience to do it. It took skill and time. He did not even aim at interchangeability. However, the general adoption of the micrometer, 927 perhaps our most useful measuring instrument, has changed all this. The skilled mechanic has become the toolmaker and devotes his time and skill to providing the means whereby the unskilled operator produces by hundreds the parts of mechanisms which assemble with- out fitting. Better means for making close measure- ments have called for better means for manufacturing to close limits, and these in turn have called for still greater refinements in measuring instruments. Specifying Tolerances Which Cannot Be Checked It is unfortunate that many people have come to speak familiarly of thousandths and ten-thousandths without any conception of what those quantities mean in metal. Take, for example, a ring gage, nominally one inch. By holding it in the hand a few moments it ean readily be warmed 16 deg. Fahr., which would ex- pand it a ten-thousandth. Take also a plug which fits the gage very freely, so that it can be felt to shake, and place a strip of cigarette paper one-quarter inch wide and one-thousandth thick, between the plug and the ring; the result will be a tight fit. Take another plug which will just drop through the ring by its own weight, and a third plug, which is just half a ten-thousandth larger, will fit so snugly that it will not shake off. A fourth plug, whose diameter is greater by another half ten-thousandth, will not enter the ring dry. By coating the surfaces with light oil the plug will enter the ring and slide freely as long as it is kept moving, but when it is allowed to come to rest for a moment the two are apparently frozen together, and cannot be broken apart. There are no satisfactory means for measuring the diameter of this ring except by measuring the diameter of a plug on which the ring fits. But which one of these plugs does the ring fit? It must be that the oil Fig. 2—Steel Blade Used for Punching Armature Disks film has some thickness, and yet the plug would not enter the ring without oil. It appears that the ring is actually stretched by the oil film. This illustrates the difficulty of manufacturing to close limits when we have no direct means for measur- ing. We frequently send out plug and ring gages which have a “freeze fit,” and the customer returns them, claiming that the ring is smaller than the plug because he cannot get them together. The plug is capable of direct measurement, and measurements by different operators and in different laboratories, using different instruments, will agree more closely than some would believe. But who can say what is the inside diameter of this ring? We can expect no agreement on this point. Yet draftsmen will calmly place on their IE tn en TD 928 THE IRON AGE drawings tolerances which cannot possibly be checked, and leave the gage maker and the inspector to fight it out. Too often this is done conscientiously, in the belief that high-class work is thereby assured. Good Practice in Establishing Tolerances Precision in manufacturing is not a thing to be set on a pedestal and worshipped. It costs money and time. Where it is necessary to the proper functioning of a mechanism it is worth whatever it may cost. In most mechanisms which require close fitting there are but few critical dimensions which need be held to close limits. For any manufacturing operation the tol- erances given should be the widest which will assure satisfactory operation, but no wider. Anything closer than that is economically unsound. It is particularly SIDES OF CUTTER 7O BSE GROUND ANG LAYPED TELY PARALLEL PARALLEL WITHIN OOOSF SIDES OF CUTTER TO SE GROIUNO ANDO LAPPED 2. — ———————— ry 4 —— \ / 65) | 850 | | \ [849 | ec tas ceed Gal L ‘ L i y 9 |. .|-3205 1.-|: 32015 32025 ENDS TO GE GROUND LVYOS TOBE GROUNO ABSOLUTELY PARALLEL WCALLEL NWYTH/IN.OO Tit EACH OTHER AVO AVO WITAN OO, i SQUAK VW/TH SIDES SQUARE WTA S/OES VOTE LIM/T ONALL DEC/MIAL LQMENS/ONES (5 Z. 0009 Figs. 3 and 4—Original and Revised Drawings of Cutter, Showing Changes in Tolerances unwise to place close tolerances on a drawing and then permit deviations by special dispensation. If work outside of established tolerance is usable, it proves that that tolerance is too close and should be widened in the interest of economy. Adherence to the estab- lished tolerances can usually be assured by correctly designed limit gages. The gages should be made inside the limits but as close to them as practicable, first cost and maintenance both being considered. They shoulé then be used as fixed limits. The “Go” gage should go and the “No Go” gage should not go, and no gage should be forced, otherwise its life will be short. Two Examples of C'ose Measurements Let us cons:d me actual examples of close meas- urements which have been made, and some which could not be made, at least at any reasonable cost. The Pratt & Whitney company recently made some thread gages for an automobile manufacturer, for which a definite gage-maker’s tolerance of 0.0002 in. in pitch diameter was given. The customer rejected them as undersize. On checking them it was found that they were within tolerance, and they were accordingly sent back. The customer again rejected them, giving his readings on each individual gage. The author took them to the Bureau of Standards for checking. Using 5 lb. pressure on the anvils of their measuring ma- chine, over wires laid in the angle of the thread, their readings checked those of the author’s concern with a variation of 0.00001 in., or one hundredth part of the thickness of a cigarette paper. Their readings were within the specified tolerance. But when using only 2 |b. pressure their readings were 0.00014 in. larger, a difference of two-thirds of the specified tolerance. The customer specified no conditions of temperature or pressure under which the gages should be measured, yet a reasonable variation in either one would have made all the difference between acceptance and rejec- tion of the work. The author’s company has made up a set of 24 steel cylinders as shown in Fig. 1. They are of steel, highly finished, and according to our readings the greatest variation from 1 in. diameter at 68 deg. Fahr. was March 27, 1924 -+-0.000002, —0.000000. They made a similar set «¢ 25-mm, cylinders. The measurements in both eas were made by the interferometer, based on Professoy Michelson’s determination, some 30 years ago, of : number of cadmium-red light waves in the internationa| meter, and the ratio between the inch and meter esta} lished by Congress in 1866. Six of each lot of cylinders were sent to the Nationa Physical Laboratory at Teddington, England, for check. ing. They were measured on the millionth comparator, against their own standard inch which was derived from the British imperial yard stick. They worked at their standard temperature of 62 deg. Fahr., making the necessary correction for expansion at 68 deg. Fahr. It was found that the cylinders would yield 0.000004 in, under the anvil pressure of 2 lb. which they used. The British inch is 3.3 millionths shorter than the inch used by our Bureau of Standards. Making corrections for these factors, their average reading for the six cylinders varied from that of the author’s company by 0.8 of one millionth of an inch. The agreement on the metric cylinders was even closer, coming within 0.4 of one millionth of an inch. Close Tolerances in Commercial Work Consider now some practical examples taken from everyday commercial business. Fig. 2 is a steel blade used by the thousand in a large shop for punching armature disks. The tolerances are close, but not par- ticularly troublesome, with the exception of the radius 1.4117 with a tolerance of +0.0001, —0.0000. The author’s company knew of no means by which this dimension could be measured or checked, and therefore refused several times to bid on the work. The pur- chaser resented this, saying that the parts had been made for several years from the same drawing, both in their own tool room and in four outside shops, with- out ever having a rejection on this point. Asked how the radius was checked, no answer was forthcoming. But the purchaser finally agreed to remove the tol- erance figures from this dimension, and to accept any +0 904 preren == " | | Fig. 5—Tolerances on an Automobile Transmission Gear product which they could not prove wrong. One may wonder why the figures were ever placed on the draw- ing. Fig. 3 shows another piece, used in some quantity, on which a quotation was asked. Tolerances where given were close but possible. In quoting the author's company interpreted +0.0000 to mean that these dimen- sions were to be held within 0.00005 in., which could be done. “Absolutely parallel” was somewhat compre- hensive, but the company offered to hold this to 0.000005 in., for we could measure that. “ Absolutely square” corners could not be measured, but they under- took to hold this to 0.0001 in. on the short dimension, as an error of this magnitude would show daylight when an accurate square was applied. The customer came back with the statement that March 27, 1924 the company’s price was high, “probably because their tolerances were too close.” He inclosed a_ revised drawing (Fig. 4) on which the tolerances were about ten times those the company had asked. A price was then made which was about one-third that originally quoted, and the order was obtained. In the first in- stance the pieces would have had to have been lapped and measured in a constant-temperature room. The change made it a fairly simple job of grinding. The customer saw what his unnecessarily close tolerances would cost him. Example of Impractical Requirement The following is an inquiry for gages, apparently for ordinary shop use in a plant building motor trucks: We request standard list prices and best discounts on double end reversible plug gages of your standard design made up to the following tolerances: Gage Tolerances (One Way or Total Tolerance) Class Go No Go A .00002 00002 KB 00004 00004 Cc 00006 90006 bD 0001 0001 > 0001 00015 No statement is made as to how or at what tem- perature the gages would be measured, nor as to the Fig. 6—Two Spur Gears Meshed With Each Other diameters required. The tolerance of 9.00002 on a l-in. Class A gage represents the change in size which would be caused by a temperature change of 3 deg. Fahr., or on a 2-in. gage by 1% deg. Fahr. Such gages, though expensive, can be supplied, but of what use would they be in the shop? An hour’s use would wear them out of tolerance. Notice also that in one case the gage tolerance on the “No Go” is greater than on the “Go.” It should obviously be less, because the “Go” gage wears, and it wears toward the limit if its tolerance has been properly placed, while the “No Go” gage, if made within limits, wears away from the limit. It can wear but little unless forced, and there is no inducement to force it because to do so rejects work which might pass. It is logical to make the gage-maker’s tolerance on the “No Go” half as great as on the “Go”? member. Why Production of Smooth Running Gears Is Difficult The shop drawings of a certain automobile trans- mission gear: gave the dimensions and tolerances as shown at the bottom of Fig. 5. The only important dimension is from the shoulder to the bottom of the hole, shown at the top. This did not appear on the drawing until a lot of gears had been spoiled. The end of the gear fitted nothing and might have varied a thirty-second of an inch. The tolerances as originally placed made it necessary to hold two dimensions, one of them quite unimportant, to a tolerance of 0.002 in. each, while the revised figures above gave a single dimension with a tolerance of 0.004 in. Smooth-running gears are about as difficult to pro- duce as anything which passes through the machine shop, chiefly because of the lack of means for meas- uring the one essential dimension. Outside diameter, tooth thickness, backlash, eccentricity, ete., can be directly measured, but they are of secondary im- portance. Various involute testers have been devised, but they do not give directly the controlling dimension. In fact, the truth of the involute is not important so long as the two mating tooth forms are conjugate; THE IRON AGE 929 that is, for perfect action each-must generate the other. Fig. 6 shows two spur gears meshed with each other, The heavy line represents the straight-sided basic rack from which the involute teeth are generated and with which they will run. The perpendicular distance Pn between the parallel faces of two adjacent rack teeth is the normal pitch, which is the perpendicular distance between two parallel planes making simultaneous con- tact with two adjacent tooth profiles. It is equal to the developed length of the are on the base circle sub- tended by one tooth. It determines the angular move- ment of the gear while that tooth is in action. If the tooth spacing is not uniform this angular movement varies. If the mating gears are not conjugate in form and of the same normal pitch, the driven gear will either be bumped ahead or allowed to drop back as each tooth of the driving gear comes into action. An error of 0.0001 in. in normal pitch is of the same order of importance as an error of 0.001 in. in any other dimension of the gear. This is only beginning te be appreciated. The author has a beautiful booklet, issued about a year ago by the makers of one of the best- known fine cars in America, featuring their ground transmission gears, which it is claimed are held to an accuracy of 0.0005 in. A gear having an error of 0.0005 in. in normal pitch would be rejected by most makers of second-rate cars. Device for Direct Measurement of Normal Pitch Fig. 7 shows an instrument devised to give, for the first time, a direct measurement of normal pitch. It consists essentially of two plane parallel faces, A and B, corresponding to two rack teeth the distance be- tween which is variable and readable in ten-thousandths by means of a multiplying lever and dial indicator. By means of this it is possible to tell before removing a gear from the grinding machine whether it will run smoothly with any other gear whose normal pitch is known, and make corrections if needed; also to match up any gear of which there is a record. This is offered as an illustration of the value of direct means for measuring any dimension which must be held to close limits. Until this instrument was developed it was Fig. 7—Instrument for Direct Measurement of the Normal Pitch of Involute Spur Gears not possible to tell whether a gear would be satisfac- tory until it had been run with its mate. If it was not there was no way of telling what correction was needed, The one critical dimension could not be measured. Two new types of induction motor are now being marketed by the General Electric Co. The SCR single- phase motors are designed for constant speed at 60, 50 or 40 cycles, in sizes from % to 10 hp., and are in- terchangeable for 110 or 220 volt circuits. The KT-900 type is a riveted frame, polyphase induction motor, of three- and two-phase squirrel cage, 60 cycle design, and is being sold in sizes ranging from % to 15 hp. Morris Shapiro, Baltimore, subject to his tender being accepted by the court, has purchased the Groton Iron Works, New London, Conn., at auction, for $203,- 000. The property purchased heretofore was used for the construction of vessels. nie 930 THE IRON AGE New All-Geared Drill and Tapper The all-geared sliding-head drilling and tapping ma chine illustrated, designated as the No. 263, has been added to the line of the Barnes Drill Co., Rockford, IIl., taking the place of the former 26-in. unit having the same swing. A self-oiling system has been added and radial bearings provided for all shafts in the speed- change transmission, including crown gears and drive shaft bearings. Eight geared speeds and eight geared feeds are available. The machine may be equipped either with the square column and rectangular table shown, or with a round column and table. Other features include a spur geared feed, which is emphasized as eliminating the usual worm and worm gear and saving considerable replacement expense. The reduction in the spur geared feed gives finest feed of 0.005 in. per revolution of the spindle. The speed changing gears are cut from bar stock chrome-nickel steel, heat treated and tempered. The method of attaching the rack to the spindle sleeve is also regarded as an improvement, screws and dowels having been eliminated and the rack dovetailed into the sleeve and keyed in position. This is intended Radial Journal Bearings for Speed Change Trans- mission, Including Crown Gears and Drive Shaft Bearings, Are a Feature. Spur geared feed is used, and the rack is dovetailed into the sleeve to eliminate the trouble caused by screws and dowels working loose. The machine is rated to drive a 2-in. high-speed twist drill at 0.041 in. feed per revolution of the spindle or at the rate of 6% in. per min. in cast iron, without the back gears. It is claimed to drive a 1-in. high-speed twist drill at the rate of 13% in. per min. in cast iron. Suitable feeds are available for boring bar work, the machine being rated to bore out an 8-in. or larger hole. The spindle is 14% in. in diameter and is double splined. For tapping, a reversing friction clutch gear giving a reverse speed of 1% to 1 is employed and these gears are on the driving shaft of the machine rather than cn the spindle. A trip may be set so that when the top reaches the depth required the spindle will reverse auto- matically, backing out at increased speed. The shifting lever may be set so that when tripped it will return to neutral position, stopping the spindle instead of revers- ing it. Direct motor drive may be applied, a 5-hp., 1200- r.p.m. motor being recommended. The floor space re- quired for the machine is 24 x 49 in., and the height is 94 in. The weight of the No. 263 drill is 2000 Ib. net. March 27, 1924 Five Societies to Participate in Internatio),,| Management Congress Arrangements for American participation in th ternational management congress, to be held at Pracy Czechoslovakia, July 21 to 24, are in the hands of repy. sentatives of the Taylor Society, management divi: of the American Society of Mechanical Engineers, Ame, ican Management Association, Society of Industria] F; gineers, and National Association of Cost Accountan| Engineers interested in management, but unaffiliated with these societies, are also invited to attend. Th secretary of the committee in charge of arrangement: is Dr. H. S. Person, managing director Taylor Societ, 29 West Thirty-ninth Street, New York. The five general subjects to be considered at th, congress are: Management in general, industria] map. agement, management in quasi-public basic industries. management in public administration, and education of management. Pittsburgh Safety Meeting Preventing accidents and conserving health will be the two main topics discussed at a safety conference of the engineering section, National Safety Council, to be held in Pittsburgh, April 1, under the auspices of the western Pennsylvania division of the National Safety Council. The general topic of the morning session will be “Safety Committees—their Organization and Main- tenance.” John A. Oartel, Carnegie Steel Co., will be chairman and J. M. Woltz, Youngstown Steel & Tube Co., will speak on “Safety Committees Will Die, Unless Fed. What Shall We Feed Them?” Other speakers include C. B. Auel, Westinghouse Electric & Mfg. Co., whose address will be on “Accident Records—What to Keep and How to Keep Them.” “What Is Industry Doing to Cut Down Time Loss on Account of Illness,” is the topic to be discussed at the afternoon session, at which C. J. Stein, M. D., medical director, Philadelphia will be chairman. Among the speakers at the session will be A. W. Colcord, M.D., chief surgeon, Clairton Works, Carnegie Steel Co., who will address the conference on the subject of “Infections.” Lists of Dealers and Importers in Foreign Countries Are Compiled WASHINGTON, March 25.—The Commercial Intelli- gence Division, Department of Commerce, has compiled trade lists of dealers and importers in foreign countries, copies of which may be obtained from the Bureau in Washington, or any of its district or cooperative offices. Among the list are the following: Iron and steel, im- porters and dealers, Egypt, NE-14034-A; automobile body builders, British South Africa, BE-6052; automo- bile tops and bodies, builders, Canada, BE-1042; body builders, top builders, New Zealand, FE-24034; automo- tive products, importers and dealers, Germany, EUR 4006; automotive products, importers and dealers, Austria, EUR-15007. Lt. Col. Walter C. Sweeney, general staff, U. S. A., will be the guest of the Boston branch National Metal! Trades Association at Young’s Hotel, Boston, Tuesday evening, April 1. During the first year of the war, Colonel Sweeney was at General Pershing’s headquar- ters and subsequently chief of staff 28th Division during the Meuse-Argonne drive. He is now intelligence officer first corps area, comprising the New England States. He will deliver an address at the meeting on the radical and revolutionary elements as they exist today in the United States. The production of gears by special grinding machin- ery is to be discussed before a meeting at Toledo of the American Society of Mechanical Engineers 0” March 20 by R. S. Drummond, vice-president Gear Grinding Machine Co. * March 27, 1924 New Radial Drilling Machine Convenience of operation, inclosed gearing, ‘“‘fool- proof” elevating mechanism and simplified lubrication are among the features of the new 6-ft. radial drilling machine recently placed on the market by the Dreses Machine Tool Co., Cincinnati. The head is entirely inclosed, as shown in the illus- trations, and is