THE UN I VERSITY OF MICHIGAN COLLEGE OF ENGINEERING Department of Mechanical Engineering Final Report GENERAL MACHINABILITY STUDIES ON THREE GRADES OF STAINLESS STEEL Part II AUTOMATIC SCREW MACHINE L. V. Cplwell K0 N. Soderlund ORA Project 03654 under contract with: UNIVERSAL-CYCLOPS STEEL CORPORATION BRIDGEVILLE, PENNSYLVANIA administered through: OFFICE OF RESEARCH ADMINISTRATION ANN ARBOR February 1961

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TABLE OF CONTENTS Page LIST OF TABLES v LIST OF FIGURES vii ABSTRACT ix OBJECTIVE xi INTRODUCTION AND GENERAL CONCLUSIONS 1 THE MATERIALS INVESTIGATED 3 TEST SETUP 5 OPERATING CONDITIONS 7 TEST PROCEDURE 9 TEST RESULTS 13 Light Forming 13 Heavy Forming 13 Turning 20 Drilling 20 Chasing 20 SPECIFIC CONCLUSIONS 23 iii

LIST OF TABLES Table Page I, All Conditions of Test 7 II. Forces, Surface Roughness, Dimensional Change 10 III. Tool Wear - All Materials 11 V

LIST OF FIGURES Fig. Page 1. Test piece and operational sequence. 6 2. Units-force vs. piece number. 14 3. Trends of slopes. 15 4. Trends of slopes. 16 5. Surface roughness vs. piece number. 17 6. Lines deflection vs. piece number. 18 7. Surface roughness vs. piece number. 19 8. Units-force vs. piece number. 21 vii

ABSTRACT Extensive tests on an automatic screw machine were made in comparing toolwear characteristics, feeding forces, surface quality, power requirements, and dimensional stability of the work materials. In general, the MA grade performed as well as, and in some respects better than, the M material. The 18-8 required the highest forces in cutting and in most cases this difference was substantial. ix

OBJECTIVE The purpose of this investigation was to analyze the machining behavior of the different grades of stainless steel under conditions similar to those occurring under production runs. xi

INTRODUCTION AND GENERAL CONCLUSIONS The short sharp-tool tests, which have been reported in Part I, have revealed some significant facts about the relative performance of each grade of material. Tests of this nature do not always indicate how a material will behave under prolonged cutting. Tool wear may give rise to changes in, for example, cutting forces, dimensional stability, power requirements, and surface quality. An extensive test which permits relative evaluation of these factors is desirable since any one or combination of them may be used as a criterion of tool failure. Tests on a Brown and Sharpe automatic are useful for this purpose. The general conclusions are: 1. From the standpoint of an over-all performance, the MA grade exhibited the best machining behavior. 2, The machining of the 18-8 was generally the most difficult, 1

THE MATERIALS INVESTIGATED Part II of the test program was composed of two phases: 1. The material (annealed) used for Phase 1 was the same as used in Part I. The stock was centerless ground to 63/64-in., and coded as 18-8, 18-8M, and 18-8MA. 2. For Phase 2 the material (cold-worked) was received centerless ground to a 1-in. diameter, and tagged 303MA (yellow) and 303 (red). The designation of 303MA was kept and 303 was coded 303M. 3

TEST SETUP The shape and size of part and the operational sequence used in a Brown and Sharpe, No. 2G, single-spindle automatic screw machine are shown in Fig. 1. The part was designed to reveal information on six basic machining operations - light and heavy forming, turning, drilling, reaming, chasing, and cutoff. Force dynamometers mounted on the front and rear slides recorded the feeding forces on the light- and heavy-form tools. Strain gages mounted on the follower arm of the turret slide measured the turning feeding force and drill thrust, The forces were recorded on Sanborn recorders. Power requirements were recorded on a Esterline-Angus wattmeter for the various machining operations, 5

5 3~ REAM 9/16 x 3/8" DEEP.93l5.875 DIA. 35 DRILL 64 3/4-16 N.F. REAR FORM a CUT-OFF (Heavy) CHASE Ia I' REAM K~ U TURN FRONT FORM (LIGHT) Spindle Speed: 290 rpm - Time/ Piece: 225 sec 1.a 9. Cut Off 6. Ream 2. Turn- 3/4 OD 7. Chose 3. Chamfer 8. Stock Feed 4. Heavy Form - 7/8 OD 9.8 1. Cut-Off 5. Drill- 35/64 Hole & Light Form- 15/16 OD Fig. 1. Test piece and operational sequence. 6

OPERATING CONDITIONS All test conditions are summarized in Table I, They remained constant for all the materials tested. TABLE I ALL CONDITIONS OF TEST Machine: Brown and Sharpe, No. 2G, single-spindle automatic Cutting Fluid: 10% Stuart's Thred Cut and Circo XXX straight oil Materials Tested: 18-8, 18-8M, 18-8MA, 303MA, 303 Cutting Conditions Spindle Veloci- Feed, Cutting Tools Operation -... Speed, ty, fpm in./rev. Material Signature rpm Cutoff 290 75.00125 *HS.S.(Clarite) 10,0,6,2,10,-2,0 Knee Turn 290 75.004 *H.SS.(Mo-Max) 0,8,6 6,6,8,1/32 Chamfer 290 75.0025 H.S. S (Mo-Max) 0, 0, 6, 0, 30, 0 Heavy Form 290 75.00125 H.S.S.(Clarite) 10,0,6,0,0,0,0 Drill 290 41.0033 HoS.S. Nat'l 118~ Point Angle Twist Drill.Stdo 15~ Relief Angle Screw Machine Oxide-Treated Front Form 290 75.0005 H.S.S.(Clarite) 10,0,6,0,0,0,0 Ream 290 43 o009 H. S, S Nat' 6 Blade Spiral (.0015/ Twist Drill.Std. Flute blade) Machine Reamer 45~ Chamfer Chase 290 57.0625 Geometric H.S.So 3/4-in,-16 N.Fo Style 3/4 15" Hook Angle Milled for Stainless Steel * 18%W - 4%Cr - l%Va. 7

TEST PROCEDURE Each material was tested under identical tool setup and cutting conditions, and the length of a test was defined as 300 pieces for the 18-8MA, 18-8M, 303MA, and 303M, On the 18-8, the test was ended by complete failure of the turn tool, The standard test procedure consisted of (1) properly setting all tools to produce parts within specifications; (2) machining of parts, with collections of all pieces in the exact sequence as produced by the machine; (3) recording light- and heavy-form feeding forces, turning tool feed force and drill thrust, and power requirements at intervals of 15 pieces; and (4) periodic visual inspection of the cutting tools during the run, with final inspection at the end of the test, All surfaces on each part were inspected visually for significant changes in surface appearance. In addition, surface-roughness measurements were made on the formed surfaces with a Micrometrical Profilometer, and the same diameters were measured with a micrometer to record the dimensional change over the life of the test. The results of the foregoing are plotted and shown under "Test Results," Visual inspection was the only observation made of the threads, cutoff surfaces, and the drilled and reamed holes. 9

TABLE II FORCES, SURFACE ROUGHNESS, DIMENSIONAL CHANGE Surface Roughness Dimension MatLt __Force - lb |, 4 - rms Change (in. ) Mat' | Light Heavy.Light Heavy Light Heavy - _ Form Form Tn D Form Form Form Form Max.-176.0 Max.-512.6 Max.- Max.-1380.0 18-8 Min.-147.2 Min.-450.0 (1) 1150.0 Min.-1207.5 20 12-22 0.003 0.007 Ave.- Ave. -481.3 (Tool Failure) Ave.-1265.0 *(1) 154.0 (2) — 586.5 (2) 166.0 Min.- 362.3 Ave. - *(1) 391.0 (2) 431.3 H 0 Max.-126.0 Max -297.5 Max.- 316.5 Max.- 868.0 *() 140-180 18-8M Min,- 80.0 Min.-250.0 Min.- 253.0 Min.- 747.5 100-130 0.002 0.002 Ave. -118.0 Ave.- Ave.- 287.5 Ave.- 805.0-120 *(1) 256.3 (2) 283.5 Max.-115.2 Max,-275.0 Max.- 299.0 Max.- 793.5 18-8MA Min.- 88.8 Min.-235.0 Min.- 241.5 Min.- 701.5 130-150 120-160 0.0012 0.0021 Ave.-106.0 Ave. -243.8 Ave.- 270.1 Ave.- 728.3 Max, -134.4 Max. -312.5 Max. - 3235 Max. - 897.0 303MA Min.-108.0 Mino-287.5 Min.- 281.8 Min.- 793.5 60-70 70-100 0.001 0.003 Ave. -116.0 Ave. -297.5 Ave. - 304.8 Ave. - 851.0 Max.-157.6 Max.-307.5 Max.- 345.0 Max.- 828.0 0-80 *(1) 40-80 303M Min.-124.0 Min.-262.5 Min.- 299.0 Min.- 690.0 120-140 0.0017 0.004 Ave.-138.0 Ave. -281.5 Ave.- 330.6 Ave,- 709.3 * Represents 2 distinct levels.

TABLE III TOOL WEAR - ALL MATERIALS Tool 18-8 18-8MA 18-8M 303MA 303M Turn Tool failed at 195.0095 radius wear.007 radius wear.0096 radius wear.0062 radius wear pieces. Failure on and chipped. Flank and chipped..002 and/or smear. Even small chipped area flank at the inter- edge-.024 smear regular wear pat- wear pattern on on flank of.0035. section of OD and region on flank. tern on flank. flank of.002. No other wear on cutting edge. Regular wear of Slight evidence of B.U.E. not mea- flank detectable..0081 reading-wear. smear pattern of built-up edge. surable. No B.U.E. discernVery slight evi-.009 to.013. ible. dence of built-up Built-up edge very edge. noticeable. Heavy.0034 wear in a.0033 wear and/or Regular wear pat- Even wear pattern.0038 wear near Form very even pattern, smear. Chipped tern max. being on flank of.0028. center of tool. Very slight evi- edge of.001..0025 and smear in.007 corner wear Other wear even at cence of built-up Built-up edge pre- evidence..0059 cor-.0055 B.U.E. di-.002. B.U.Eo of edge. dominant at.008. ner wear. Slight rectly above cor-.0032 on corner evidence of built- ner wear. only. up edge. Light Even wear pattern.0035 wear and/or.003 wear and/or Even wear pattern Regular wear patForm of.0034. No evi- smear. Built-up smear. Built-up on flank of.0036. tern of.0037 on dence of built-up edge.0035. edge of.002. Corner wear.016. flank, Corner wear edge. Spotty B.U.E.-max. of.008. B.UoE.0036 at corner, uniform at.0022 across cutting edge. Drill.005 max. wear..0057 max. wear.007 max. wear.008 max. wear.006 max, wear Smear and/or wear and/or smear. Cor- and/or smear. Cor- and/or smear. Large and/or smear. Large on corner of.0168. ner smeared heavi- ner smeared heav- B.U.E. at chisel BoU.Eo at chisel Chisel edge chipped ly. Large built-up ily. Large built- edge. (=o024) of 2 edge of o.021 of 2 badly, edge in area of up edge at chisel segments adjoining segments adjoining chisel edge, Chis- edge. each cutting edge. each cutting edgeo el edge chipped. Heavy smear on corners and margins.

TABLE III (Concluded) Tool 18-8 18-8MA 18-8M 303MA 303M Cutoff.010 corner wear..0032 smear and/or.0057 smear and/or.0015 wear and vis-.0016 wear and visEven wear pattern wear. Built-up edge wear. Built-up edge ible smear of o0045. ible smear of.004 of.004 of o0085. of.007. Corner wear.005. with even pattern, B.U.E -. 0053. Reamer Wear of.0035 on Wear and/or smear Wear or smear of Approx..020 wear Approx..015 wear corner of blade 4. of.0118 on corner.0126 on corner of and/or smear on and/or smear on All other corners of blade 4. All blade 3. All other blades 4, 5, and 6. corner of blades less. others same condi- corners same condi- Other blades 1, 2, and 6. Slight tion but less in tion but less in.,0054. wear and/or smear magnitude. magnitude. on other blades, Chasers Chaser No. 3 max. Chaser No. 1 max. Chaser No. 1 max. No chasers used. Chaser No. 1 max, H corner wear of smear and/or wear smear and/or wear smear and/or wear thread of o010o of.018. Max. built- of.015. Max, of.011. B.U.E. Heavy smear on up edge of.006 on built-up edge of found on chaser chaser No. 4. first thread on.006 on first No, 3 on threads chaser No, 1. thread on chaser 1 and 2 of approx, Slightly less B.UE. No. 2. B.U.Eo ap-.004. on first thread on prox. same for the 3 other chasers, other chasers.

TEST RESULTS LIGHT FORMING Feeding force values and surface-roughness readings are plotted in Figs, 2 to 5 inclusive for the light-forming operation on each of the materials tested. This operation most generally gave rise to discernible differences between the materials tested. The feeding force for the 18-8 was higher than either the 18-8M or 18-8MA, either in the annealed condition or cold-worked. The 18-8MA (and 303MA) exhibited the lowest forces, whether annealed or coldworked. Referring to Figs. 3 and 4, the 18-8M and 303M exhibited slightly higher force readings and the trends of the slopes were consistently of a higher level. Referring to Table III, tool wear for the form tool was very nearly the same for all the materials, as reflected in the relatively small differences in the forces produced by each material, This indicates the sensitivity of each material relative to tool wear; the 18-8MA and 303MA appeared least sensitive. The surface quality obtained in this operation can be considered to be the predominant factor in evaluating the performance of the materials, especially between the MA and M grades. The 18-8 produced the best consistent surface finish, both by profilometer measurements and by visual comparison, The MA and M grades produced approximately the same level of quality with one exception described later. Referring to Figs, 2 and 5 and Table II, the general concept of higher force producing a better finish is substantiated with the 18-8M and 18-8MA materials. But contrasting the 303MA versus 303M, the quality of the 303M deteriorated considerably, The cause for this reversal is not fully understood, but it is interesting to note (with reference to Figs, 3 and 4) the trends of the force and surface finish readings, Apparently the built-up edge entered quite significantly in producing a poorer finish. It is significant to note in Table III the extent and pattern of B. UEo on the tools, The character of the BoUEo was affected by cold-working the material (303MA and 303M), which substantially improves the surface finish of these grades, HEAVY FORMING Figures 6 and 7 represent the results of feeding force and surface-roughness for the heavy-forming operation on each of the materials, The results are quite similar to those obtained for the light-forming operation, The most 13

Mot'/- 18-8 Rese 42- Die Head 40 38-1 1 \ Light Form 4 O//L Me 20 40 60 80 100 120 140 160 180 200 27 2 Light Form 21 2 lJ 4 I I I i I I I 0 40 80 120 160 200 240 280 320 32_ Mot l - 18-8 M 30 0 24- 22D 20 / Light form, I I I I I I.I I I J I I I 0 40 80 120 160 200 240 280 34 - Mot'/- -303 MA 32 30 28 0 40 80 120 160 200 240 280 40 Mat'/- 303 M 384 #/IL n ~0 40 80 120 160 200 240 280 PIECE NUMBER Fig. 2. Units-force vs. piece number. lk

8 r - 18-8 M _ ^7 _~- 18-8MA 6 - FORCE 5 3:- / - -~ 2 I,, 0 20 40 6 80 100 120 140 160 180 200 220 240 260 280 300 ILJ ^I DIMENSION 0o 0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 z 6 SURFACE ROUGHNESS 4 - 3 2 - 0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 PIECE NUMBER Fig. 3. Trends of slopes. 15

5 A 8 -- 303 M - ~ 303 MA / \ 6 / /.. FORCE 4o I I I I I! I!! I, I I I I 1 0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 (D z 2 K D/MENSION (/)0 \- 0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 z 6 \ SURFACE ROUGHNESS 4 - 5- \ 3 2 0 20 40 60 80 100 120 140 160 180 200 220 240 260 280300 PIECE NUMBER Fig. 4. Trends of slopes. i6

4 MOt'/-/8-8 20.. Light Form I I I I l I l I l I l I l I I I I I 0 20-22 40-42 60-62 80-82 100-102 120-122 140-142 160-162 180-182 22 MA,o I:~ I..:....::: I::..'.":"I: I:I: I — OSO 160 L-ght F 120_ h S:::..:.:,......... Z _ko. ~,.,.~: -~::~:i..:.\/.. =..::,:...................................V:::.:.."'.!!'':".::.....:': ":' ol 0 40 80 120 160 200 240 280 0 160 Fig. 5. Surfcro Ier (981 ~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~(~~~~~~~~~~~~~~~( l~~f~~~~~~~~l(';: ~~~~~~~~~~~~~~~~~~~I, 1~~~( 80~~ ~:)2~~~~~~~~~~~ ~~~~~~ ~ 40.. 80: 120 160 200 240 280~rr~~r~~r~~~~~~~~~~~ P2~~~l..r~~:"""" ~ IIIIECE NUMBER~~~~~~~~ 17~~~~~~~ (~~~~~~ ~~~~~~~ ~ 5

38De36- 34 Heavy Form 1 25 /L/ne,. I, I.. I, I I I 20 440 60 80 00 1 120 140 160 180 200 23, \Maotl-18-8MA 21 19 Heavy Form 1/2.5 #L/ L ine I I I I I I I I I I LJ 0 40 80 120 160 200 240 280 z z23 Mot -i8-8M * I,19,I Heavy Form 12. 5,/L ine 0 40 80 120 160 200 240 280 26 i Motl- 303MA 24 22 Heavy Form 12.5 /L ine 0 40 80 120 160 200 240 280 24_ Mat'1-303 A A 22 Heavy Form 12.50/L ine 20 " i I l I i I 0 40 80 120 160 200 240 280 PIECE NUMBER Fig. 6. Lines deflection vs. piece number. 18

6T' aqum-u assld sn ssullBL I1 ase;rnS 1 *21, 38'J!nN 3031d 08Z O0Z 00 091 OZI 08 Ob 0 I' I....' I' I' I' I f I' Ot' r ~~ ~........... 08 IV ~O11- /,/DI -091 083 0t'z 00; 091 OZI 08 Oti 0:' I'. ".' I'' I',': I'~::~~::: _ I I I I wo_, (I I I1 08a C3 00~ 091_ 03l 08 Ot' 0 ) 08 I 1 111 III.... 0? 0 0:.::::: O::::O,'1 08 O Vsvv 0 s00 x,,,;,,\,,,..,,.._........ yo_4' A./,,..... 7Z E:~::y.,.,,.,.,..,,,,,,,.. _ 08Z 00; OOZ 091 O I 08 Ob 0 C) uaJO_4 A'Ao H _H O,k 080........i 0 tt tii ~~~~~~ ~~~~~~~~~I ~~~~~~~~~~~~~~~~.~~..~~..~::~~~ ~~~... ~~., ~ ~~~~.....,..,...00,..

pronounced differences appear in the magnitude of the forces recorded. Referring to Table II, the force for the 18-8 is approximately two times greater than that for the 18-8MA or the 18-8M, and slightly less than two times greater than the force produced on the 303MA and 303M. Tool wear for the heavy-form tool was very similar in magnitude for all the materials, indicating the sensitivity of the materials relative to tool wear in affecting the feeding forceo The surface quality obtained on the materials with this forming condition is in line with the quality produced by the light-forming condition~ On the 303MA and 303M grades, cold-working the material improves the surface quality significantly. TURNING Figure 8 shows the feeding-force results for the turning operation for each material. The forces recorded for the materials closely follow the pattern established for the light-forming operation. The 18-8MA and 303MA have lower force values than the M grade materials, whether annealed or cold-worked, with no tendency to increase as the test progresses. Referring to Table III, the built-up edge is very prominent for the 18-8MA and 18-8M materials, but not present on the 18-8, 303MA, and 303M gradeso This corroborates that the presence, amount, and stability of the BoUoEo exerts a predominant role in the resulting surface qualityo DRILLING The thrust force of the drill is the largest of all the forces measured in the test runs. The values are in agreement with the trends as produced by the other operations. The surface quality of the drilled hole was much better for the 18-8 than the other materials, compared visually. The finish for the cold-worked MA and M was somewhat better than the annealed grades. Whether the MA and M were annealed or cold-worked, no definite distinction could be made between the quality of the drilled holes. CHASING Thread surface quality was good on the 18-8, and the finish for the other grades was much lower in quality. No distinction could be made among the MA or M materialso 20

Mot'/-18-8 Preliminary.10 Too Failure Die Head Tool Turn Tool - Setting 575 /Line,I I I i i I l lIl I l I, ] I I I 0 20 40 60 80 100 120 140 160 180 200' 0 40 80 120 160 200 240 280 LJ (r Mat'-I18-8M IL 4 Turn Tool- Turret -c 5 575/Line 0 40 80 120 160 200 240 280 J Mat'/1-303 MA 4 Turn Too/ Turret - 575 #/Line,I I I I I I I I I I I I I I 0 40 80 i20 160 200 240 280 MaMot - 303 M Turn Too/-Turret 5 575 /Li ine 0 40 80 120 160 200 240 280 PIECE NUMBER Fig. 8. Units-force vs. piece number. 21

Size was difficult to maintain for a class 3A thread in the 18-8 material, but t he other materials presented much less of a problem in attempting to hold the thread tolerance over the entire run. 22

SPECIFIC CONCLUSIONS 1. 18-8MA, 303MA versus 18-8M, 303M. (a) The MA and M grades produced forces of approximately the same magnitude (b) The 303MA produced a significantly better surface quality on the light-form operation, while, on the heavy form, finishes of similar quality were produced for both materials, (c) The MA material on the average produced lower dimensional variationo (d) Built-up edge was generally less for the 303MA, (e) From the standpoint of general machining characteristics (chip handling, vibration, etc.), the MA and M materials were good. (f) There was no large amount of wear present on the turn tools of the above materials after approximately 18-1/2 hr of actual cutting time. 2. 18-8 versus all other grades. A superior surface quality was consistently produced on the 18-8 material for all operations. (a) Forces were always substantially higher for the 18-8. (b) The dimensional change for the 18-8 was fairly pronounced. Accuracy was difficult to maintain in the chasing operationo (c) Tool failure occurred on the 18-8 turn tool at approximately 12 hr of actual cutting time. (d) The general machining characteristics of the 18-8 was only fair compared to the other materials. Chip handling was difficult, and vibrations(chatter) were always present, though not to a large degree. 23

UNIVERSITY OF MICHIGAN 3 III015 02841 246111111 3 9015 02841 2461