THE UNIVERS I T Y OF MI C HI GAN COLLEGE OF ENGINEERING Department of Mechanical Engineering Final Report COMPARATIVE MACHINABILITY OF MBMC-1 AND AISI 4130 STEEL L. V. Colwell K. N. Soderlund UMRI Project 03690 under contract with: INGERSOLL DIVISION BORG-WARNER CORPORATION KALAMAZOO, MICHIGAN administered by: THE UNIVERSITY OF MICHIGAN RESEARCH INSTITUTE ANN ARBOR October 1960

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TABLE OF CONTENTS Page LIST OF TABLES v LIST OF FIGURES vii ABSTRACT ix I. STATEMENT OF THE PROBLEM I II. GENERAL CONCLUSIONS 3 III. DEFINITION OF MACHINABILITY IV. THE MATERIALS INVESTIGATED 7 V. TEST PROCEDURES AND RESULTS 9 A. Tool Life with High-Speed Steel Tools 9 B. Tool Life with Carbide Tools 14 C. Cutting Forces-Turning 25 D. Drilling Torque and Thrust 26 E. Energy Requirements 3 VI. SPECIFIC CONCLUSIONS 37 iii

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LIST OF TABLES Table Page Id Hardness and Size of Test Specimens 7 IIo Tool Life with HSS Tools and As-Forged Work Materials 13 III. Tool Life with HSS Tools and Heat-Treated Work Materials 13 IV. Summary of Cutting Force Equations 26 V. Drilling Torque as a Function of Feed Rate and Drill Diameter 32 VI. Drilling Thrust as a Function of Feed Rate and Drill Diameter 32 VII. Cutting Energy for Milling 36 v

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LIST OF FIGURES Figure Page 1 Tool-life: Rough turning with high-speed steel (as-forged). 10 2 Tool-life: Finish turning with high-speed steel (as-forged). 1I 3 Tool-life: Finish turning with high-speed steel (heat-treated). 12 4 Tool-life carbides. 15 5 Tool-life carbides. 16 6 Tool-life carbides. 17 7 Tool-life carbides. 18 8 Tool-life carbides. 19 9 Tool-life carbides. 20 10 Tool-life carbides. 21 11 Tool-life carbides. 22 12 Tool-life carbides. 23 13 Tool-life carbides. 24 14 Cutting force "Fc" vs. size of cut. 27 15 Feeding force "'IF vs. size of cut. 28 Drilling torque vs. feed and drill diameter. 30 16 Drilling thrust vs. feed and drill diameter. 31 17 Drilling tlrust vs. feed and drill diameter. 51 18 Cutting energy for AISI 4130 steel. 34 19 Cutting energy for MBMC-1 steel. 35 vii

ABSTRACT Both tool life and cutting force studies were made on the two work materials in both the as-forged and heat-treated or hardened condition. In general, the MBMC-1 steel was more difficult to cut. However, it was feasible to cut it satisfactorily at all test conditions except for turning the hardened material with high-speed steel tools. Quantitative data provide a general guide for shop practice. ix

I. STATEMENT OF THE PROBLEM The principal objective was to determine whether the newly developed, highstrength steel MBMC-1 exhibited any unique characteristics which would make it particularly difficult to machine. For this purpose it is necessary to explore tool wear behavior as well as force and energy requirements at a number of different conditions such as turning, drilling, and milling. Since many of the quantitative data cannot be interpreted on an absolute basis, it was decided to obtain comparable information for AISI 4130 steel which is functionally similar to MBMC-1. 1

II. GENERAL CONCLUSIONS It was determined that, although the MBMC-1 steel does exhibit some unique machining properties, it can be machined with no great difficulty, particularly in the as-forged condition. When it is hardened it cannot be cut readily with high-speed steel tools but it can be cut quite satisfactorily with both sintered carbide and ceramic tools. 3

III. DEFINITION OF MACHINABILITY To avoid misconception, machinability should be defined in specific terms. Two criteria, used to compare the relative machinability of the test materials, have been selected for this investigation. One is the magnitude of cutting force required to machine the materials, using several types of operations and at varying sizes of cut. Low cutting forces are more desirable than high cutting forces and demonstrate better relative machinability from this viewpoint. Relative machinability may also be based on tool life. A material that exhibits a longer tool life than another is considered to have better machinability from this viewpoint. Unfortunately, a high machinability rating based upon one criterion does not always indicate corresponding advantages with respect to other relevant machining criteria. Materials that cut with lower forces do not necessarily exhibit better tool life. Force measurements obtained with sharp cutting tools are not indicative of the nature of tool wear that will result if the cut is continued. A material may show a low force at the start of cut but exhibit a poorer tool life than a material which shows a higher starting force; this could be accounted for by different wear rates not reflected in the forces. The term "better machinability," if properly applied, should be considered only in terms of the criteria of interest. References such as surface finish and dimensional stability have not been studied per se in this work and specific comments pertaining to these items should not be considered conclusive. A fundamental study of the type conducted is intended to bring out any pronounced differences that might exist, but the conclusions from any investigation are limited to the actual testing conditions. If, for example, sintered carbide tools are used in a study of tool life, the findings of relative machinability could be of a different order from those obtained with highspeed steel tools. 5

IV. THE MATERIALS INVESTIGATED TABLE I HARDNESS AND SIZE OF TEST SPECIMENS Size of Hardness Work Piece WorkIdentin Work Brinell** Brinell Average Piece. in. Reading (mm) Reading (mm,)* Hardness Number 4130-1-H (heat-treated) 5 OD x 24 2.8 2.85 461 4130-2-H 5 OD x 24 2.6 2.85 461 4130-3-AF (as-forged) 5 OD x 24 4.6 4.7 163 4130-4-AF 5 OD x 24 4.55 4.45 183 4!0-^5 1 x 2 x 36 4.5 4.65 167 B.W.-1-H (heat-treated) MBMC-l 5 OD x 24 2.95 3.05 401 B.W.-2-H 5 OD x 24 2.7 2.85 461 B.W.-3-AF (as-forged) 5 OD x 24 4.3 4.4 187 B.W.-4-AF 5 OD x 24 4.3 4.o 229 B.W.-5 1 x 2 x 36 4.3 4.4 187 *Obtained at University of Michigan with a 10-mm steel ball and 3000-kg load. **Provided by sponsor. 7

V. TEST PROCEDURES AND RESULTS A. TOOL LIFE WITH HIGH-SPEED STEEL TOOLS Work specimens used were in the form of cylinders, with an approximate OD of 5-1/4 in. and 24 in. long. Each test consisted of a lathe turning cut at a constant size of cut and cutting velocity until complete tool breakdown occurred. The total elapsed cutting time, from starting point to failure, constitutes the tool life for those operating conditions. The cutting speed was changed for each tool-life test, thus providing a relationship between velocity and tool life. Each material was subjected to such tests until enough individual points were obtained to define both level and slope of the velocity, tool-life line on logarithmic coordinates. Upon the conclusion of each individual test and prior to the subsequent test, a cleanup cut was taken to avoid any possible effects of work-hardening from the previous tool failure. Test Conditions and Equipment. -Two Monarch engine lathes equipped with variable-speed drives were used for all tests in this series. All machining was done dry, that is, without a cutting fluid. Standard 3/8-in.-square "MoMax," high-speed steel tool bits were ground to the signature, 0, 8, 6,6,6, 15, 1/32. The roughing cuts on the as-forged materials were made at a feed rate of 0.015 ipr and a depth of 0.100 in. For the finishing cuts on the same materials the feed was 0.0052 ipr and the depth was 0.020 in. In cutting the 4130 heat-treated material, the feed rate was 0.0075 ipr and the depth was 0.050 in. Attempts at cutting the heat-treated MBMC-1, resulted in an extremely poor cutting action and no consistent data could be obtained at any size of cut. Test Results. -Figures 1 through 3 contain test results plotted on loglog coordinates. The trends are shown as straight lines which may be described by equations of the general form, VTn = C, where: V = cutting velocity (at OD) in fpm, T = tool life in minutes, C = a proportionality constant, and n = slope of the tool-life line. In all cases, the lines represent average performance but dispersion of points around the individual lines is not pronounced. 9

~600 TOOL LIFE-TURNING 400 400 -~-~ ~ -~~- — ~~- - - ~ ~ ~-~- ~- - -~~- -- ~ -~ -~~- 300 -now 4130 200 80~ 100 - - -- - - ------- 60 40 MAT'L 4130 (AS FORGED)-~ —- -- ~ MB~MC.T1 (AS FORGED) TOOL MAT'L H.S. 20 TOOL SIG.0.8.66.66.15.1/32 ___ DEPTH 0.100 IN FEED 0.015 IPR ii^ FIG. I TIME (MINUTES) ~ 10 ~3 p - 01 0.2 0.4 1.0 2.0 4.0 10.0 20.0 400 Fig. 1. Tool-life: Rough turning with high-speed steel (as-forged).

IIII, I' I I I1 600... TOOL LIFE-TURNING ~ ~ ~~~~ — ~- MBMC^..... {t ~~~^^ ~ ~ ~~~-430 400 - w "e _......,...', I.... —, _ 300 MBMC #1 200 100 - ~. ~. H80 ~ —~. ~. 60 _.. MAT'L 4130 (AS FORGED) ) T MBMC*1 (AS FORGED) TOOL MAT'L H.S.S. 20 _ TOOL SIG.0,8,6,6,6.15,1/32 -- - — ____ DEPTH 0.020 IN FEED 0.0052 IPR___ II FIG. 2 TIME (MINUTES) 10 1I I I lI l l l l I i I I _.a I I I I I I I I 0.1 0.2 0.4 1.0 2.0 4.0 10.0 20.0 40.0 Fig. 2. Tool-life: Finish turning with high-speed steel (as-forged).

___ II I II I I I I I I II I IIII! I I I! 1111 ___ 600 ^600F~~~~ 1TOOL LIFE-TURNING 400 - - - - -, 300 200 80w I 60 m- mm L II- -~! m - 1 60 _.-. -. -- ~.... -~_~~ - 40 MAT'L 4130 (HEAT TREATED) TOOL MAT'L.H.S.S. 20 TOOL SIG. 0.8.6.,6.15.1/32 DEPTH 0.050 IN FEED 0.0075 1 PR 10 ~~.~~~ I FIG. 3 TIME (MINUTES) L 10~ a I I i1 ~I I I I!I 1 1\~ ~1 0.1 0.2 0.4 1.0 2.0 4.0 10.0 20.0 40.0 Fig. 3. Tool-life: Finish turning with high-speed steel (heat-treated 4130).

Equations for the resulting tool-life lines are summarized in Tables II and III. TABLE II TOOL LIFE WITH HSS TOOLS AND AS-FORGED WORK MATERIALS MaterialEquations ___ _ aRoughing Cuts* Finishing Cuts** 4130 vTO.08 = 192 VT0.0s55 = 440 MBMC-1 VT0.12 = 125 T.12 = 15 *Depth = 0.100 in.; Feed = 0.015 ipr. **Depth = 0.020 in.; Feed = 0.0052 ipr. TABLE III TOOL LIFE WITH HSS TOOLS AND HEAT-TREATED WORK MATERIALS Equations Material MatiRoughing Cuts* Finishing Cuts 4130 VT0.0682 = 71.3 ** MBMC-1 **_-___ **-.___ *Depth = 0.050 in.; Feed = 0.0075 ipr. **Cutting behavior at these conditions proved to be impractical and the erratic quantitative results are irrelevant. Conclusions (1) Both AISI 4130 and MBMC-1 demonstrate orderly behavior in the as-forged condition when cut at both roughing and finishing conditions. (2) It is impractical to try to remove substantial amounts of MBMC-1 by cutting it in the heat-treated condition with high-speed steel tools. 13

(3) The steeper slopes of the tool-life lines for the MBMC-1 indicate that tool wear is more abrasive in nature than when cutting AISI 4130 steel. (4) Cutting speeds for MBMC-1 should be approximately 40* lower than those found to be appropriate for AISI 4130 steel, B. TOOL LIFE WITH CARBIDE TOOLS Procedure.-~The same specimens used for the HSS tool study in (A) were used for this series of tests. Test procedure consisted of operating a cutting tool at a given velocity, feed rate, and depth of cut. The carbide insert was removed from the toolholder at predetermined time intervals and the flank and rake face were examined under a toolmaker's microscope The wear on the flank of the cutting tool was measured and recorded. This procedure was continued until a typical carbide wear pattern was established. Test Conditions.-The machines were the same as those reported in (A). The tools were 1/2-in.-square, mechanically held blanks. The Kennametal toolholders provided a tool signature of -5, -5, 5, 5 15, 15, 1/32. The sizes of cut for both roughing and finishing of both the as-forged and the heattreated materials were the same as used for machining the as-forged material with high-speed steel tools. Unlike high-speed steel tools, carbides do not fail abruptly. Instead, the wear is gradual and point of failure is arbitrarily defined by a limiting amount of wear. Consequently, the tools were examined at regular intervals and the wear measured. Test Results. —The results of tool wear measurements are shown plotted against elapsed cutting time in Figs. 4 to 13 inclusive. These represent a significant range of cutting conditions and carbide grades with both work materials. Figures 4, 5, and 6 show the behavior for the as-forged materials. Three different grades of carbide were tried with a roughing cut on the MBMC-1. The results in Fig. 4 show that Carboloy-350 was best when compared to grades 370 and 883. This indicates that MBMC-l is not particularly abrasive in the cutting behavior despite its silicon content. Figure 5 gives a comparison of MBMC-l with AISI 4130 for roughing cuts and Fig. 6 gives a similar comparison for finishing cuts. The results indicate that both materials can be cut at substantially the same speeds and sizes of cut while in the as-forged condition. Test results for the heat-treated condition are summarized in Figso 7 to 13 inclusive, Figs. 7 to 10 for roughing cuts and Figs. 11 to 13 for finishing cuts. Once more Carboloy-350 was the best grade of carbide as indicated in FIgso 8 and 9. Combining this experience with the variable speed tests of Fig. 7 led to the comparison plotted in Fig. 10 which shows that cutting speed for 14

TOOL LIFE-TURNING 883 AT 500 FPM LO MAT'LMBMC#1 (AS FORGED) II20-T ~ ~~ ~~ ~~ -__TOOL MAT'LVARIED CARBIDE 0 TOOL SIG.-5.-5.5.5.15,15,1/32 - DEPTH 0.100 IN FEED 0.01 53 IPR o t SPEED VARIED FPM 883 AT 400 FPM -LJ / 1 I I T^ ~~-370 AT 500 FPM LL 350 AT 500 FPM, — ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ F IG.A TIME-MINUTES 0 10 20 30 40 Fig. 4. Tool-life carbides.

~I I TOOL LIFE-TURNING..j MAT'LMBMC#1 (AS FORGED) ~ ~ ~ ~ ~~I. 4130 (AS FORGED) / c In TOOL MAT'L 350 CARBIDE L T___ ___ ___ ___ __ TOOL SI G.- 5,5,5.5,15,15,1/32 20'"~ i DEPTH 0.100 IN z I I FEED 0.0153 IPR — _.........._ ___ _ SPEED 500 FPM -MBMC-I1 600 FPM- 4130 /0 Fig. 5...f TIME -MINU TES Fig... Tool-life carbides.

TOOL LIFE-TURNING ~~~ MAT'L MBMC- (AS FORGED) ~ ~ ~~ I4130 (AS FORGED) -. I n I I I TOOL MAT'L 350 CARBIDE LI _ _ TOOL S I G.-55,-'5.5,5.15.15,1/32 ~20 - - IDEPTH 0.020 IN... z I FEED 0.00521PR _ —....... |$l l SPEED 500 FPM -MBMC#1 - _ __ _ __ 600 FPM-4130 0 ~ ~~~~~I~~~Fg6.To-iecrie r- MBMC#I U__ 413-FG - ^^T~ ~ ~ ~ ~ ~ ~~TIME- MINUTES 1L10 Fig. 6. Tool-life carbides. 0 10 20 30 40 Fig. 6. Tool-life carbides.

~i ~ ~~ TOOL LIFE-TURNING 30 {,~ t MAT'L MBMC#1 (HEAT TREATED) _ i _ ___ ___ _ __ TOOL MAT'L 350 CARBIDE -_ | TOOL SIG.-5,-5.5.5.15.15,1/32 ~ ~, ~~- D DEPTH 0.100 IN - FEED 0.0153 I PR I - ~~ - SPEEDVARIEFPM - I ~~; i 20 _ _ _ I _ _50~~~~~~~: - 7.!li i _ _ _ I _ _ _ ___./~-150 125FPM _~ F7~i 7 T-ool arbide00 FPM ~7 70^~~L^^ 7)ME - MINUTES 0 10 20 30 40 50 Fig. 7. Tool-life carbides.

III I1i1I TOOL LIFE-TURNING LO I l l MAT'L MBMC#I (HEAT TREATED) L _ ________________TOOL MAT'L VARIED CARBIDE_______ u TOOL SIG.-5-5.5.5.15.15,/32 z DEPTH 0.100 IN _- o ~ ~~ FEEDO.Q153 IPR 0 SPEED 125 FPM CLi __ __ __ __ __ TIME- TMINUTES _: I < Fig8 8. Tool-life carbides. ~~J__ __ Fig. 8. Tool-life carbides.

I'i I I t'. __.._.._ L TOOL LIFE-TURNING MAT'L 4130 (HEAT TREATED) ____.____ __ TOOL MAT'L VARIED CARBIDE TOOL SIG. 5-5.-5.5.15.15,1/32 __) I. ____ DEPTH 0.100 IN 20 - ~ -. FEED 0.0153 IPR U SPEED2.00 FPM rJ - ~ ~~Tt370=~~ z _._._ _ _ _._._ i _ _ 0 I LL 350 ~o ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ __~ - FIG. 9 /0~~~~ ~~TIME- MINUTES 0 10 20 30 40 Fig. 9. Tool-life carbides.

i i i _________ i ~ TOOL LIFE-TURNING _ _OLTOI O L -— _I _ 30 _ _ _ _ MAT'L MBMC#1 (HEAT TREATED) t I I I~ 4130 (HEAT TREATED)-,~ l | TOOL MAT'L 350 CARBIDE 1~~ ~ ~ ~ ~ ~ ~~ TOOL SIG. -5-5,5, 5,15,15,1/32 - T"' _ DEPTH 0.100 IN -= ~ ~ ~ ~ ~ ~ ~~|| -FEED 0.015 IPR 20b~ ~ 200 FPM -4130 x \ ~ i F 20 ^ -Q~~~~~''4 0 71__ __ ___ __ ___ __ __ __ _ _TIME-MINJTES_3 0 10 20 30 40 50 Fig. 10. Tool-life carbides.

_~ ^~'.I TOOL LIFE-TURNING ~~ 30 MAT'L MBMCl (HEAT TREATED) TOOL MAT'L VARIED CARBIDE. TOOL SIG.5.,-5.5.5.15,15,1/32 DEPTH 0.020 IN __ FEED 0.0052 IPR 5-~ ~ ~ ~ ~ ~ ~- SPEED 200 FPM - 2 - 1 I i 0 - _1 _ __ __NUTES1 0 10 20 30 050 Fig. 11. Tool-life carbides.

TOOL LIFE-TURNING _ _i I I _ _ _ _ _ _ _ MAT'L 4130(HEAT TREATED) I___ I___ _ _ TOOL MAT'L 350 CARBIDE ____ __ TOOL SIG.-5 -5.55.515.15.1/32 Ld^~~~ ~DEPTH 0.020 IN 20 -t I FEEDQ.QO52IPR ___ O SPEED VARIED FPM 10 I ru, I L I 300 FPM ~-,- 1 - __ __ __ __ _ I'I II__TIME M INUTES i 0 10 20 30 40 Fig. 12. Tool-life carbides.

I! TOOL LI FE - TURN ING 30 L~ I MAT'LMBMC#1 (HEAT TREATED)I.________ __ 4130 (HEAT TREATED).. __ TOOL MAT'L 350 CARBIDE ~~~ ~ ~ - TOOL S I G.- 5,-5,5,5,15,15,1132 2 L__ i DEPTH 0.020 IN _ 5-~~~~~ FEED 0.0052 IPR -~ ~ _- _ SPEED 200 FPM 20 0 -EEO O2P i i 413010~~~~ H I _ _ 0 -_________________________ TIME- MINUTES______ 0 10 20 30 4050 Fig. 13. Tool-life carbides.

the heat-treated MBMC-1 must be reduced 40-50% below that for hardened AISI 4130 for roughing cuts. On the other hand, Figs. 11 to 13 show that MBMC-1 can be cut at approximately the same speed as AISI 4130 for finishing cuts. Conclusions (1) Carboloy Grade-350 carbide or equivalent is best for both MBMC-1 and AISI 4130 steels in both the as-forged and the hardened conditions. (2) MBMC-1 can be cut at the same conditions as AISI 4130 except for roughing cuts on hardened material. (3) Cutting speeds for hardened MBMC-l must be reduced 40-50% below those used for rough-turning of hardened AISI 4130 steel. C. CUTTING FORCES-TURNING The hardened materials only were subjected to a series of turning tests to determine the magnitude of cutting forces with carbide tools since the toollife tests indicated that this type of tool material must be used for the heattreated MBMC-1. Similar information for high-speed steel tools and as-forged work materials was obtained by drilling and milling as reported in (D) and (E). Test Conditions and Procedure. -The feed rate and the depth of cut were varied in several combinations while the tool shape, tool material, and cutting speed were held constant. All work materials were subjected to the same test procedure wherein readings of cutting force (perpendicular to the plane of tool motion) and feeding force (parallel to axis of work rotation) were obtained for lathe turning cuts. A 14-in. swing Monarch engine lathe was operated at spindle speeds which produced surface velocities of 200 fpm for the heat-treated 4130 and 100 fpm for the heat-treated MBMC-1 steels, respectively. Feed rates for the 4130 were 0.0038, 0.0076, and 0.0153 ipr, while the depth of cut was maintained constant at 0.100 in. Similarly, the effect of depth of cut was evaluated at depths of 0.020, 0.040, 0.060 and 0.100 in. with the feed held constant at 0.0076 ipr. Feed rates for the MBMC-1 were 0.0028, 0.0038, 0.0056, 0.0076, 0.0112 and 0.0153 ipr, while the depth of cut was constant at 0.100 in. Corresponding depths of cut for a constant feed rate of 0.0076 ipr were 0.020, 0.030, 0.040, 0.060, 0.080 and 0.100 in. The tool signature for all tests was -5, -5, 5, 5, 60, 30, 1/32. Readings of feeding and tangential forces were obtained simultaneously on a dynamometer equipped with electric-resistance strain gages. No cutting fluid was used. 25

Test Results.- The effects of feed rate and depth of cut on the cutting or tangential force are shown in Fig. 14. The 4130 steel exhibits a true exponential trend. The equation for this line takes the general form F = KfXdy, where: Fc = cutting force in lbs., K = a proportionality constant, f = feed rate in ipr, d = depth of cut in in. and x and y = exponents. Table IV contains the equations derived for this material. The MBMC-1 exhibits nonlinearity and discontinuity. Consequently the equations represent only the maximum forces. This phenomenon appears to be sensitive to the rate of energy release and probably to temperature as wello Spot sampling indicates that abrupt increases in forces occurred at lighter cuts when the cutting speed was higher. The effects of feed and depth on the feeding force are shown in Figo 150 An exponential trend is clearly shown for the 41309 but again the MBMC-1 exhibits unstable cutting at certain combinations of conditions. TABLE IV SUMMARY OF CUTTING FORCE EQUATIONS Material Equations Force Component 4130 Fc = 88 350f~70 do3 Tangential Inch Ff = 11,550f4 d84 Feeding MBMC-1 Fc = 63,500f~ d~ Tangential Inch Ff = 8100f'20 d293 Feeding D. DRILLING TORQUE AND THRUST The two work materials (as-forged) were drilled at several different cutting conditions to determine the effects of feed rate and drill diameter on 26

700 I I - CUTTING FORCE vs. FEED & DEPTH ~ 500 ~ ~~~4l~00 _~M~ ~MB MC #1: -x i - 400 MBMCI1 I I I I I 40___ M F^ -__ ___ T.l,__*'Tl_____|_ DEPTH 0.100 IN.___ ______ 4130 200 ~TOL S. -,-5 6 I -I \ l SPE ED 1 = f —MM BM #1 i 1200 MBMC# 1 80 C 60 FEED 0.0076 IPR DEPTH 0.(10 IN. 40 30 -ri MATL MBMC# (H-EAT TR.EATED) _~~ 4130 (HEAT TREATED) TOOL MAT'L 883 CARBIDE 20 -TOOL SIG. -5Fi55,5,560.30.1/32 SPEED 100 - MBMCI 1 200 FPM- 4130 FIG. 14 DEPTH (1x10-3 INCHES) FEED (lx10-3 IPT) 10. 10 20 40 60 100 2 3 4 6 8 10 20 Fig. 14. Cutting force "F" vs. size of cut.

I__ -- ~ IIII= 111 1 ~ I II1I III ___ ~ | ~- FEEDING FORCE vs. FEED & DEPTH I 200- -- - - 80l' I I 1I 41___.30 - 100 > - - - -I- -? - 1 80 r - - - - r' -1~~ - - - -1 - - -z:: I I~ I MB IMC I1 I I 60 40 - FEED 0.0076 IPR DEPTH 0.100 IN. 30 - -- - MAT'L MBMC#1 (HEAT TREATED) - MBMC#1 _ 4130 (HEAT TREATED) TOOL MAT'L 883 CARBIDE 20 __ TOOL SIG. -5,-5.5.5.60.30.1/32 SPEED 100 FPM -MBMC# 200 FPM - 4130 FIG. I II I I I 1111 111i i I DEPTH (1x10-3 INCHES ) FEED (1x10-3 IPT) 10. 10 20 40 60 100 2 3 4 6 8 10 20 Fig. 15. Feeding force "F " vs. size of cut. vsnie fct

torque and thrust requirements. Procedure.-Test specimens were in the form of rectangular pieces, 1 x 11/4 x 4 in. long. The workpieces were held in a vise on a dynamometer and drilled at a particular feed rate and cutting velocity. When the readings of torque and thrust stabilized, the cut was discontinued. The same procedure was followed for both work materials. A sharp drill was used for each test. Several tests were duplicated to check the repeatability of the results. Test Conditions.-All tests were conducted on a Fosdick 25-in., box column, upright drill press at a cutting velocity of 35 fpm. All drilling was done dry. Drills were standard high-speed steel, two-fluted twist drills. They were ground to a point angle of 118~ and a relief angle of 6~. The helix angle was 30~. Web thicknesses are listed below. Drill Diam., in. Web Thickness, in. 0.250 0.043 0.375 o.066 0.500 0.082 0.625 o0.86 At constant drill diameter of 0.375 in., the feed rates were 0.005, 0.007, 0.009, and 0.011 ipr. At constant feed rate of 0.005 ipr, the drill diameters were 0.250, 0.375, 0.500 and 0.625 in. A dynamometer containing wire-resistance strain gages was used to obtain readings of torque and thrust. Test Results.-Figures 16 and 17 show the results plotted on logarithmic coordinates. The effects of drill diameter and feed rate on cutting torque (lb-in.) and thrust (lb) show a uniform behavior or exponential trend. Such straight lines may be represented by equations of the general forms T = KfaDb and B = CfXDy where: T = cutting torque in lb-in. (sharp tools), K = a proportionality constant, 29

DRILLING TORQUE vs. FEED & DRILL DIAMETER CUTTING VELOCITY 35FPM _ CUTTING VELOCITY 35FPM DRILL DIAM. 0.375 IN FEED RATE 0.005 IPR 200 -------- 1 - MBMC#1 4130 100 z —— / _ - - ___ 80 ~ --- ---- ~- ~ __~ 0 2-^MBMC#1or ~ ~ — -___ 60 w ------ I -- - - - - -- 4130430::==1 -= =-: —= 30 H- _~~~~~~~~~~~~~~~ 20 FIG. 16 FEED (1x10-3 IPR) DRILL DIAMETER (1x101 INCHES) 10'". 1 ~~ 2 3 4 5 6 810 20 1 2 3 4 5 6 810 Fig. 16. Drilling torque vs. feed and drill diameter.

l~~~I1II~ I,! I I!1 I III I I I!I"! 11'l DRILLING THRUST vs. FEED & DRILL DIAMETER CUTTING VELOCITY 35 FPM. CUTTING VELOCITY 35 FRM DRILL DIAM. 0.375 IN _ FEED RATE 0.005 IPR 1000 - -- -- - _ - - I 800 - - I I~I I I ~ I I~~ ~ ~~~ - M B M C # 1 600 ~ MBMC 1 ~- __, 400~ ~ ~^ 4130 ___ 300 200 —-- FIG. 17 FEED (1x10-3 IPR) DRILL DIAMETER (1x10- INCHES) 100'L 1 I I I I l i I I I I 2 3 4 5 6 8 10 20 1 2 3 4 5 6 810 Fig. 17. Drilling thrust vs. feed and drill diameter.

f = feed rate, ipr, D = diameter of dr-ill, inches, a and b = slopes of lines showing the effects of feed and drill diameter on torque, B = thrust force in lb (sharp tools), C = proportionality constant, x and y = slopes of lines showing the effects of feed and drill diameter on thrust. Tables V and VI contain the equations derived ffrom the straight lines. These can be used to calculate the torque and thrust when drilling the two materials (as-forged) and are most applicable within the range of variables actually used in this study. TABLE V DRILLING TORQUE AS A FUNCTION OF FEED RATE A~NID DRILL DIAMETER Material Equations 4130 T = 47,650f0" 6D2.03 MBMC-1 T = 7;230fo 57Dl 88 TABLE VI DRILLING THRUST AS A FTNCTION OF FEED RATE AND DRILL DIAMETER Material Equations 4130 B = 76,450f~' 77D.54 M3MC-1 B = 30,85Of0~5 8D 38 32

Conclusions (1) The effect of feed rate on torque is more pronounced for the 4130 material as can be concluded from the slope of the lines. (2) At the higher feed rate the torque for both the MBMC-l and 4130 are the same for the given drill diameter. (3) The MBMC-l exhibited higher torque readings consistently relative to the effect of drill diameter. (4) The effect of feed rate on thrust is also more pronounced for the 4130 material (5) Effect of drill diameter on drill thrust resulted in consistently higher forces for the MBMC-l material. (6) The most important difference between the two work materials is that the MBMC-l does not cut as well nor as efficiently at small feed rates. E. ENERGY REQUIREMENTS Energy requirements were measured directly with a pendulum type dynamometer in a milling cut. High-speed steel tools with a rake angle of 8~ simulated average shop conditions. Test Conditions and Procedure. -The HSS cutting tool had a width of 0.245 in., 8~ radial rake angle, 6~ side clearance angles, and 12~ end clearance angle. Ten cuts were made at a depth of cut of 0.100 in. and a feed setting of 0.003 ipt; the work advanced 0.003 in. for each successive cut. After the above cuts were made, tests were run at a feed setting of 0.006 ipt for ten cuts, then changed to 0.010 ipt for another ten cuts. The above sequence of feed settings was repeated at depths of cut of 0.060 in., and 0.020 in., ten cuts being taken for each combination. The same procedure was used for both work materials. Test Results. —Figures 18 and 19 show the results plotted on logarithmic coordinates. The effects of feed (ipt) and depth of cut upon the energy requirements can be expressed by the equation: E = Kfxd 33

i i I ~~~~~~~~~~ 1 1 7 I I I NET ENERGY PER CHIP vs. FEED & DEPTH ____-_- -- __ MAT'L 4130 - -- 30 — TOOL MATL H.H.S. 30 ~ ~ ~ - - - ~ ~ - -'~ RADIAL RA KE _ 20Li_ d f 0.0.10 IN 10 ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~~~fOO0P U _____ 0.10 0 IN \_ _ ^'^ ~ ~ - -^ ^ - ~-r^ ^~~~~~~~~ ^ ^ ^ f = 0.0 0 6 1 P R 41 _Z.1~ — -~ ~ I I __oe, IyT~ 4 I 00el-~ -1_ - — ~ - - ~ -~ — --- i_~L^ ~^ ~~~~~~^~~~~~7z FEED(1x10I3 PT) \ DEPTH (1x03 INCHES) 2Z 3 4 6 810 20 20 40 60 100 Fig. 18. Cutting energy for AISI 41i0 steel.

I I I I I 11! /'! I'' i I I I 1! I I 1!1111 NET ENERGY PER CHIP vs. FEED & DEPTH __ iz ll Izzlzzjzz::zzzuzI I - - 30I - - - ___ - TOOL MAT'L HH.S. r30 l l^~ RADIAL RAKE 8I 20 -- ------- - -- -- H.m'f= 0.010 I PR u., ^^ ^ = 0.006 / PR d- = 0.100 IN - 06P TE.&] ~ II I V I dz00601 - 6 — d d-0 0 0.00 4 PR H- - - ________. _. >w 3 I Ii _ _ _ _ _ _ _ _ __ __ 1 —— 1f- 4 _ I FEED (1x10 IPT) DEPTH (1x10-3 INCHES ) 2 3 4 6 810 20 20 40 60 100 Fig. 19. Cutting energy for MBMC-1 steel.

where: E = energy in ft-lb per chip, K = a proportionality constant for calculating energy, f = feed in inches per tooth, d = depth of cut in inches, x and y = slopes of lines showing the effects cf feed and depth on. the energy required to cut. Table VII contains the equations derived, from the straight lines shown. in Figs. 18 and 19. TABLE VII CUTTING ENERGY FOR MILLJ!NG Material Energy Equations Unit HP0* 4130 E = 2,200fn7ed0 84 1.16 MBMC-1 E = 873f 00od0.70 1.48 *Feed. 0.010 ipt; depth, 0.l00 ino Conclusions (1) The energy required to cut the MBMC-I is consistently higher for all combinations of cutting conditions. (2) Both materials exhibit a common characteristic relative to the effect of feed versus the effect of depth The above equations show that the energy per chip increases with an increase in feed and depth of cut cnly as the 0.60 power of the feed and the 0~70 power of the depth of cut for the MBM31C-l. For the 4150 the same is true, the power of the feed being 0.76 and 0.8^4 for the depth of cut. This indicates the desirability of taking heavy feeds from a power standpoint This property is common to most metals. 36

VI. SPECIFIC CONCLUSIONS (1) Tool Life with High-Speed Steel Tools (a) Cutting speeds for the as-forged MBMC-1 must be about 40% lower than for as-forged 4130. (b) It is impractical to cut heat-treated MBMC-1 with high-speed steel tools. (2) Tool Life with Carbide Tools (a) Carboloy Grade 350 or equivalent is satisfactory for both steels in both the as-forged and hardened conditions. (b) As-forged MBMC-l can be cut at speeds about 80* as high as for asforged 4130. (c) Hardened MBMC-l must be cut at about 50*-70% of the speed for hardened 4130. (3) Tool Life with Ceramic Tools (a) It is feasible to turn both as-forged and hardened MBMC-1 at speeds from 600 to 1000 fpm. (4) Cutting Forces MBMC-l produces substantially higher cutting forces than 4130 in both the as-forged and hardened conditions. Consequently, it is necessary to provide substantial rigidity to obtain satisfactory tool life, surface finish, and size control. 37

UNIVERSITY OF MICHIGAN III 015 0284i 1 2768111 11 3 9015 02841 2768