ENGINEERING RESEARCH INSTITUTE THE UNIVERSITY OF MICHIGAN ANN ARBOR Final Report MACHINABILITY OF RAILROAD-CAR AXLES.L V.o'C lwell Ko H. o"Moltrecht J. Koivula Jo. Co Mazur ERI Project 1197 BETHLEHEM STEEL COMPANY BETHLEHEM, PENNSYLVANIA March 1958

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The University of Michigan ~ Engineering Research Institute ABSTRACT The results, as shown in Table I, indicate that the average tool lives of four of the heats are close to the median at approximately four cuts. There are two heats which show greater variation from the mean. The average tool life, six cuts, for Heat Number A is well above the mean, whereas Heat Number B, at two cuts, had a tool life well below the meano In the preliminary work on the axle bodies, the Apex tools showed an average tool life somewhat above that of the Pullman Standard tools. The axle bodies appeared to show the same machining qualities encountered on the journals, as shown in Tables I and IIIo INTRODUCTION The machining behavior of two representative axles from each of six heats has been determined. Tests were carried out on standard AAR 6-ino x 11-in. plain bearing axles. Machinability was measured by tool life under journal finishing conditions TEST CONDITIONS The axles were first cut into three pieces of approximately equal length, marked as shown in Fig. 1, and the required center holes were drilledo To assure a better grip on the headstock end of the journal, the rough forged surface at this end was removed by turning. Before taking the first roughing cut, all eccentricity and scale were removed from the journal by taking a skin cut, The machinability tests were conducted on a 22-ino x 48-ino Model CM Monarch Engine Lathe equipped with a Reliance VR Variable Speed Drive. The work was held in a four-jaw independent chuck on the headstock end and on a dead. center at the tailstock end. Cutting tools used for the roughing cuts were of sintered carbide, Kennametal K-6 grade, which were ground with radii to conform to the radii of the journalo The finishing tools were of high-speed steelo Two styles of finishing tools were suppliedo One set, used only during the preliminary work, were standard Apex tools used for finishturning journals at the Johnstown Plant of the Bethlehem Steel Companyo The second set, furnished by the Pullman Standard ^~ I ~~~~~~~~~~~

The University of Michigan ~ Engineering Research Institute Company, consisted of two forged shanks on which were brazed high-speed steel tips. Identified as PH and P5, these latter tools were used for all the finish turning tests on the journals. The Pullman Standard finishing tools were reground on the face and flank after each test, maintaining correct tool shape and angles as specified by the template, sketched in Fig. 2. The tools were then hand-stoned to obtain a good surface finish and to correct minor imperfections in their contour. In the production set-up on the axle turning lathe, the tool is positioned with a back rake of approximately 5~ by means of wedges or shims. This arrangement could not be used in these tests and accordingly the 5~ rake angle was ground on the tool as shown in Fig. 3. Prior to the first roughing cut on each journal, the carbide roughing tools were reground using a diamond wheel and by grinding on the face only. The tools were set with the cutting edge 1/4 in. to 5/16 in. above the TABLE I No. of Average Heat Axle Journals Surface Finish Tool Lif Heat Journals Tool Life No_. e Tool Life Start Finish for Heat A1 5 100/120 130/150 6 2 7 100/120 110/120 3 1.5 130/150 150/170 2 _ _. 4 2.5 130/170 130/170 C 5 4.5 95/115 115/140 06 4 10o/115 150/165 5. D 7 4 120/130 130/140 8 3~e5 105/115 150/165 375 E 9 3. E ~ 9 ~ 3 e 5 ~ 120/140 160/185 ~ 2 10 3 110/125 1.0/160 35l F 11 4 90/120 150/170 4.25 12 4.5 e 120/140 150/160 l IA lB END A AXLE NO. I END 8 AXLE MARKINGS FIG. /

The University of Michigan * Engineering Research Institute IR. TEMPLATE FOR GRINDING TOOLS P5 a PH F/IG. 2 ~ 3 ~^

The University of Michigan * Engineering Research Institute 4. 5~ 2 l 100 A - TOOL SHAPE-CARBIDE ROUGHING TOOL 2o A -— _ —_ - _ 2 8i I00 20 2o 20~ 31B- TOOL SHAPE - H.S.S. FIN/SHING TOOL FIG. 3 \~ h ~^~~F/6

The University of Michigan * Engineering Research Institute centerline of the journal and with an overhang of 2 in. Final adjustments to the angular position of the tool, relative to the work, were made on the basis of observations of the surface finish and the chip formation, In all cases the roughing tools were set to cut on the centerline of the journal. The cutting conditions, summarized in Table II, also corresponded to shop practice. TABLE II..T......... Cutting Conditions Method of Feeding fpe |Cutting Cutting Depth Infeed at_/ Turning Turning Of Tool Speed, Fed of Cut, Cutn Start of 5/4-in. Bearing Cut f pm Fluid Cu Material_ __fpm_- ipr in. Fluid Cut Radius Surface Kennametal Soluble Oil Kennametal Roughing K-6 315.043.015 (Purosol 10) Manual Manual Power ~~~~Carbide ~10 water Carbide i oil Soluble Oil Finishing H.S.S. 55 6.015 (r )Manual Manual Power 10 water _____ L_______________1 oil TEST PROCEDURE The geometry of the finish-cutting tools (Fig. 3) produced a chip that was "thinned out" toward the last portion of the cut, resulting in a good surface finish until tool wear had an effect. The "thinning out" of the chip was a very important part of the problem of securing reproducible surface finishes and tool life, The proper "thinning out" of the chip was a function of the tool-setting angle and the contour of the end cutting edge. The tool setting was adjusted during the first cut of each test to obtain the optimum surface finish and chip formation. This setting was maintained for all succeeding finish cuts for any given test. After each finishing cut the surface was wiped clean and a profilometer reading was obtained using a manual tracer. To maintain uniformity, this operation was always conducted by the same person, and the speed to move the tracer head was checked with a master plate several times daily. As a permanent record, a Fax-Film replica was made at a representative location after each cut to show the general characteristics of the surface finish, including burnishing and tearing~ Estimates of the amount of burnishing, the general appearance of the surface, and the condition of the tool we r recorded at this time. Tool life was judged on the basis of tool flank weary surface roughness, the general appearance of the surface, and the Fax-Film replicas. In general 5

The University of Michigan ~ Engineering Research Institute this tool life was quite reproducible The Fax-Film replicas were extremely valuable in reviewing the individual tests and in selecting the point of tool failure o Individual heats were represented by successive pairs of axles, i.e., 1-2, 3-4, 5-6, etco To avoid as much as possible any tendency to carry over experience from one axle to its companion, the axles were tested in the following sequence: 1, 2, 3, 5, 7, 9, 11, 4, 6, 8, 10, and 12. DISCUSSION To become acquainted with the complexities of the problem, preliminary tests were made on the body portion of several axles. Sufficient length was available to give the equivalent of two journal cuts. During this stage of the work, the variables of tool shape, elevation of the cutting edge above centerline, tool-setting angles, and tool material were studied. Table III gives a comparison of the tool life between the Pullman Standard tools and the Apex tools on two different axle bodies. These results indicate that the Apex tools on the same work material have a somewhat better tool life than do the Pullman Standard tools, In all the tests there was a pronounced sensitivity of the surface finish to the tool shape and setting-angle factors. The optimum tool shape was determined during the preliminary testing and recorded on the template, shown in Fig. 2. The finishing tools were subsequently ground and honed to fit this template. The optimum tool-setting angle was determined experimentally at the beginning of each test by making slight adjustments of the cutting tool. In most cases it was possible to arrive at a relatively smooth surface finish during the first cut, as shown in the general summary in Table IV. Once the proper tool-setting angle and tool elevation were established, the lathe was set up in such a way that this tool setting could be reproduced easily during the several cuts which might be necessary to produce tool failure, In arriving at the correct tool-setting angle, it was important to attain the proper "thinning out" of the chip. When this was obtained, a good surface finish resulted until the tool was worn out. The nose of the cutting tool, which removed the largest portion of the metal during the finish cut, invariably developed a small built-up edge which resulted in excessive surface roughness. This roughness appeared on the work unless it was subsequently removed by the end cutting edge of the tool in a fine shaving action, described previously as the "thinning out" of the chip. The profilometer readings were very useful in determining that the cutting conditions were correct at the start of each test. The surface roughness, as indicated by profilometer readings, increased as the test progressed; however, 6

TABLE III I TYPICAL TEST RESULTS FOR MACHINING AXLE BODIES Cutting Useful. Cuts Surface Finish (rms) Estimated % Burnish Cutting No, Cuts ~~ ~^ Axle Tool End of n Cmet Tool to End Start of End of End of End of Comments No No, Life of Test Test Useful Test Useful Test s No, Cuts Tool Life Tool Life 6 Apex 6 10 140/160 140/160 170/180 5 20% 10% burnished at cut No, 7. ~ ^ 6 P5 5 9 120/140 120/130 150/170 5 15% Deep test marks appeared at cutNO. 6. OQ 11 Apex 6 10 130/140 120/140 150/170 10% 10% Surface finish was 110/ ^ 120 for second cut and 140/150 for cut No. 7, Deep tear marks appeared? at cut No. 7. w -3 11 PH 4 10 110/120 120/140 130/140 (Traces) 25% Cut No. 5 had 15 bur- C nish and 130/150 rms.'A C

The University of Michigan ~ Engineering Research Institute these readings were not as helpful in determining the end of the useful tool life. The general appearance of the surface, which included visual observations of tear marks and burnishing, was a more reliable indication of the end of the useful tool life. Under this circumstance, the Fax-Film replicas were of considerable help in judging the tool failure because they provided a record of the burnishing and tearing which could be used as a later reference. Some typical examples, pertaining to axles 6 and 8, of the finishes recorded in this manner are shown in Figs. 4 and 5. The areas shown have been enlarged about five times from the original. In these figures, the (a) enlargement illustrates surface conditions during the first cut; the (b) enlargements represent the conditions during the last cut which might be acceptable, and the (c) enlargements are typical of the surface generated after tool failure. In most cases tool life was selected as that point at which sharp changes in surface finish occurred, as illustrated in the (b) and (c) enlargements. All the data pertaining to the journal have been summarized by individual axles in Table IV. These results were averaged to obtain the summary given in Table I. Heats C, D, E, and F vary in tool life from 3.25 cuts per grind to 4.25 cuts with only small variations between corresponding axles of the same heato Heats A and B, on the other hand, are very different in their behavior. Heat A had an excellent finish at the beginning and the highest tool life. Heat B had the poorest finish at the beginning of the test and the shortest tool life. 8

The University of Michigan * Engineering Research Institute ao Journal No. 6B. Cut No i o b. Journal No 6B. Cut No 4o Tool No. PH. 120/130 rms. Tool No. PH. 14o0/160 rms, 5* burnished. Figo...'9 9 ~~.; ~~~brnihd.;.::~~~~

The University of Michigan * Engineering Research Institute _A t co Journal No 8Bo Cut NOo 5.Tool No. P5o 150/160 rmso 10% burnishedo Figo 5 10

TABLE IV Useful Surface Finish Estimated % Burnish | Axle Cutting Journal Diameter Tool No. Cuts End of iEnd oft xNoe Tool oLif at End Start of seful End of eful End of Comnments 3 No. Life Useful Useful O *__No. Start End No us of Test Test Tl Test ol L Test No. Cuts Tool Life Tool Life |1A to 1B P5 A-5.88 5 8 100/120 130/150 130/180 10 20 v 1A to lB P5 B-5.81 2A to 2B PH A-6.18 A-5.84 7 10 100/120 110/120 110/140 < 5 25 B-6.10 B-5.91 3A PH 6.17 5.97 1-2 3 130/150 130/150 150/180 < 5,10 < 5 Cut No. 2 has 150/170 10% burnish 3B P5 6.10 5.94 1 3 130/170 130/170 180/210 - 10 4A PH 6.18 5.78 2 7 130/140 150/160 180/210 < 5 10 5 4B P5 6.19 5.78 3 7 130/140 150/160 160/180.5 20.. 5A PH 6.15 5.81 4 6 110/140 140/180 130/155 5 10 Cut No.4 = rms = 140/180 5B P5 6.13 5.59 5(4-6) 9 80/90 90/100 110/130 < 10 30 Cut No. 7 4-100/120 4-5 rms 120/140;~^~~~~~~~~ _________________61/__-,__ 06-120/130 6-10 6A P5 6.17 5.81 4 6 80/100 160/170 140/170 10 15 Cut No. 5 r rms = 160/180 3 6B PH 6.14 5.81 4 6 120/130 140/160 160/180 5 10 15% burnish at cut No. 5 ~ A-5.84 A-5.75 4 5 120/130 130/140 130/150 10 15 7A to 7B B-6.20 B-5.89 -' 8A PH 6.14 5.91 3 4 120/130 150/170 160/180 10 10' 8A to 8B P5 A-5.90 A-5.75 3-4 6 90/100 3-140/150 150/170 3-10 20 B-6.20 B-6.06 4-10/160 4-10 9A PH 6.18 5.84 3 6 110/130 150/170 180/200 5 10 9B P5 6.15 5.84 4 5 130/160 170/200 180/210 15 20 10A P5 6.18 5.91 3 5 100/120 140/150 160/170 5 15 Cut No. 4 rms = 160/180' lOB PH 6.02 5.75 3 5 120/130 150/160 140/150 10 15 11A to l1B P5 A-5.98 A-5.81 4-150/170 150/180 4-10 20 B-6.16 B-5.94 4-5 7 90/120 5-150/170 5-10 20 12A PH 6.15 5.81 5 6 120/130 140/150 130/140 5 10 Cut No. 4, rms = 150/160 12B P5 6.17 5.78 4 7 130/150 150/170 140/160 < 10 10 Cut No. 5. -._......_______________________________ _r______________________:____ _ __. __..__o/__o__mm 3/8

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