ENGINEERING RESEARCH INSTITUTE UNIVERSITY OF MICHIGAN u M'3 CiM }56ANN ARBOR REPORT NO. 5 CUTTING SPEED VERSUS TOOL LIFE WHEN SHAPING TITANIUM WITH HIGH-SPEED-STEEL TOOLS By L. V. COLWELL R. Eo McKEE Project M993 U. S. ARMY, ORDNANCE CORPS CONTRACT NO. DA=20-018-ORD-11918 January, 1953

SUMMARY SHEET I. Engineering Research Institute, University of Michigan, Ann Arbor, Michigan. II. U. S. Army Ordnance Corps. III. Project No. TB4-15. Contract DA-20-018 ORD-11918, RAD No. ORDTB-1-12045. IV. Report No. WAL 401/109-5. V. Priority No. - None VI. Investigation of machinability of titanium-base alloys. VII. Object: The object is to investigate the machinability of commercially pure titanium and three alloys of titanium. VIII. Summary: Tool life tests were run on a shaper with 18-4-1 high speed steel tools at a constant depth of cut of 0.050 inch and a feed of 0.010 inches per stroke. All cuts were made dry. The work materials studied were SAE 1045 hot-rolled steel, and titanium grades Ti 75A, RC 130B, and Ti 150A. IX. Conclusions: 1. The machining of Ti 75A, RC 130B, and Ti 150A has been successfully performed with single-point tools in a shaper. The dependence of tool life on cutting speed is orderly and predictable. 2. The results obtained in these tests indicate a reasonable degree of similarity in performance as compared to the single-point tool turning of these materials. 3. The speeds used for a given tool life favor the Ti 75A over the Ti 150A and the RC 130B. 4. The slopes of the tool life lines obtained in these tests favor the alloy materials as compared to the commercially pure Ti 75A titanium. 5. Results of the cutting speed, tool life tests with HSS tools, under the conditions of cut used for this report, indicate the following speed ranges for a tool life (actual cutting time) of 1-40 minutes or total elapsed time of 2.6 to 195 minutes depending on length of stroke: Ti 75A, 76 to 160 fpm; Ti 150A, 60 to 79 fpm; RC 130B, 34 to 45 fpm. 6. Maximum rigidity in the machine, cutting tool, and work-holding device is a necessity in the successful machining of the titanium materials covered in this report. ii

TECHNICAL REPORT DISTRIBUTION LIST Copy No. Contractor 1 Department of the Army Office, Chief of Ordnance The Pentagon Washington 25, D. C. Attn: ORDTB - Res. and Matls. 2-3 Same. Attn: ORDTA - Ammunition Div. 4 Same. Attn: ORDTR - Artillery Div. 5 Same. Attn: ORDTS - Small Arms Div. 6 Same. Attn: ORDTT - Tank Automotive 7 Same. Attn: ORDTU - Rocket Div. ~8 Same. Attn: ORDTX-AR - Executive Library 9-10 Same. Attn: ORDIX 11-12 Commanding General Aberdeen Proving Ground Aberdeen, Maryland Attn: ORDTE R. D. and E. Library 13 Commanding General Detroit Arsenal Center Line, Michigan 14-15 Commanding Officer Frankford Arsenal Bridesburg Station Philadelphia 37, Pa. 16 Commanding Officer Picatinny Arsenal Dover, New Jersey 17-18 Commanding Officer Redstone Arsenal Huntsville, Alabama 19 Commanding Officer Rock Island Arsenal Rock Island, Illinois iii

Copy No. Contractor 20 Commanding Officer Springfield Armory Springfield, Mass. 21 Commanding Officer Watervliet Arsenal Watervliet, New York 22-23 Central Air Documents Office U. B. Building Dayton 2, Ohio Attn: CADO-D 24-25 Commanding Officer Box CM, Duke Station Durham, North Carolina 26 Chief Bureau of Aeronautics Navy Department Washington 25, D. C. 27 Chief Bureau of Ordnance Navy Department Washington 25, D. C. 28 Chief Bureau of Ships Navy Department Washington 25, D. C. 29 Chief Naval Experimental Station Navy Department Annapolis, Maryland 30 Commanding Officer Naval Proving Ground Dahlgren, Virginia Attn: A. and P. Lab. 31 Director Naval Research Laboratory Anacostia Station Washington, D. C. iv

Copy No. Contractor 32 Chief Office of Naval Research Navy Department Washington, D. C. 33 Commanding General Air Materiel Command Wright-Patterson Air Force Base Dayton 2, Ohio Attn: Prbduction Resources MCPB and Flight Research Lab. 34 Commanding General Air Materiel Command Wright-Patterson Air Force Base Dayton 2, Ohio Attn: Materials Lab., MCREXM 35 Director U. S. Department of Interior Bureau of Mines Washington, D. C. 36 Chief Bureau of Mines Eastern Research Station College Park, Maryland 37 National Advisory Committee for Aeronautics 1500 New Hampshire Avenue Washington, D. C. 38 Office of the Chief of Engineers Department of the Army Washington 25, D. C. Attn: Eng. Res. and Dev. Div. Military Oper. 39 U. S. Atomic Energy Commission Technical Information Service P. 0. Box 62 Oak Ridge, Tennessee Attn: Chief, Library Branch v

Copy No. Contractor 40 District Chief Detroit Ordnance District 574 E. Woodbridge Detroit 31, Michigan -41 Masaachusetts Institute of Technology Cambridge, Massachusetts Via: Boston Ordnance District 42 Commanding Officer Watertown Arsenal Watertown 72, Massachusetts Attn: Technical Representative 43-44-45- Commanding Officer 46-47-48- Watertown Arsenal 49-50 Watertown 72, Massachusetts Attn: Laboratory 51 Dr. James E. Bryson Office of Naval Research 844 N. Rush Street Chicago 11, Illinois 52 Ford Motor Company 3000 Schaefer Road Dearborn, Michigan Attn: Mr. R. Lesman Supervisor, Development Section Manufacturing Engineering Department Engine and Foundry Division 53-54 Engineering Research Institute Project File University of Michigan Ann Arbor, Michigan Initial distribution has been made of this report in accordance with the distribution list. Additional distribution without recourse to the Ordnance Office may be made to United States military organizations, and to such of their contractors as they certify to be cleared to receive this report and to need it in the furtherance of a military contract. vi

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN CUTTING SPEED VERSUS TOOL LIFE WHEN SHAPING TITANIUM WITH HIGH-SPEED-STEEL TOOLS This report presents the results of the initial phases of the investigation of cutting titanium on a shaper. This part of the program was devoted to the development of test procedure and interpretation of results in the absence of any established precedent for machinability studies of this type. Thus, one of the initial objectives was to determine whether an orderly relationship exists between tool life and shaping speed such as has been established in turning, for example. It was determined that an orderly relationship dOes exist and that it can be used not only to obtain relative machinability ratings but also to evaluate various practices that can be used in shaping. Only one combination of size of cut and tool shape was used with the 18-4-1 high-speed-steel tools in this initial investigation. Details are described elsewhere in this report. The four work materials used in the study were SAE 1045 steel (hot-rolled) and three grades of titanium, Ti 75A, RC 130B, and Ti 150A. SUMMARY OF TEST RESULTS Figure 1 presents the results of the cutting speed, tool life tests made with single-point high-speed-steel tools in a shaping operation. The results indicate that the cutting speed for a given tool life is higher for SAE 1045 steel than for any of the titanium materials included in this series of tests. Ti 75A closely approaches the steel, when considering the high side of the speed range shown by the cross-hatch lines, but from the standpoint of safe prediction the lower line should be used both in the case of this material and RC 130B.

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN The velocity in fpm is used as ordinate and the tool life in minutes is used as abscissa. The velocity (Vmax) is the maximum velocity computed at the center of a shaper stroke, considering that each mechanical shaper cutting stroke has a continuous change in speed from 0 to maximum to 0. The maximum velocity used in this research is higher than the average velocity which is normally established in setting a job on a shaper in a plant. The maximum velocity is emphasized in these tests because of the great sensitivity of tool life to speed. The tool life in minutes represents actual cutting time (contact time of tool with work piece). This actual time is 20.5 to 38.4 per cent of the total elapsed time in minutes, depending on the length of stroke for a given setup. Table I shows the values of C (velocity for a 1-minute tool life), n (slope of the tool life curve, V60 ( velocityfor a 60-minute tool life), and per cent V60 (based on SAE 1045 steel). TABLE I CUTTING SPEED VERSUS TOOL LIFE EQUATION VTn = C Material C n V60 Per Cent V60 SAE 1045 175.061 136 100 Ti 75A 164.097 110 81 *136.1615 70 51.5 Ti 150A 79.077 57.7 42.5 45.6.044 38.2 28.2 39.4.044 32.9 24.2 Best values based on safe prediction when cut must be made through oxidized surface. The results show that SAE 1045 can be cut at the highest speeds, with Ti 75A, Ti 150A, and RC 130B following in descending order. The value of n (slope of the curve, established by the tangent of the angle formed with the horizontal axis) favors the RC 130B, with SAE 1045, Ti 150A, and Ti 75A in descending order. The lower value of slope is normally accepted as a favorable performance characteristic. 2

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN The last column (per cent of V60 for steel) shows SAE 1045 steel at 100 per cent, Ti 75A at 51.5 per cent, Ti 150A at 42.5 per cent, and RC 130B at 24.2 per cent. This provides an index to the cutting speed relationships of the various titanium materials based on SAE 1045 steel. ORIGINAL DATA AND COMPUTATIONS Figure 2 shows the results of shaping a hot-rolled SAE 1045 steel with Firth Sterling (Blue Chip) 18-4-1 type HSS tools of the following signature: 0~ back rake, 28~ side rake, 6~ end relief, 6~ side relief, 6~ end cutting edge angle, 15~ side cutting edge angle, and 0.010-inch nose radius. The data fit a straight line with a negative slope on logarithmic coordinates. The empirical equation VTn = C represents the straight line, where V = maximum velocity, T = tool life in minutes (actual cutting time), n = slope of the curve, and C = velocity for a 1-minute tool life. This equation might be used in the following manner: V1 T1 = C T = V2 TT = V3 T Using data from the curve, 170 x 1,7n = 150 x 13n 170 = 13 = 1 150 1.7n 1-.7 1.132 = 7.65n. n =.061 Since VTn = C, 150 x 1361 = = = 150 x 1.169 = 175'. C = 175 fpm for a 1-minute tool life 35

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN and V10 10 061 = 175 V1O 175 = 152 fpm for a 10-minute tool life. 1.151 With an equation of this type, a velocity for any desired tool life or the tool life at any velocity may be determined. These data were obtained under the following constant conditions: Tool Shape - 0~,28~,6~0,60, 60,150.010 Tool Holder - Armstrong, 0~, straight Machine - Gould and Eberhardt, 32 inch, Industrial Shaper Work feed - 0.010 inch per stroke Depth of Cut - 0.050 inch Cutting fluid - None (dry cut) Size of work piece - 2 inches thick by 4 inches wide by 8 inches long. original 8 inch length remained constant. Figure 3 shows data obtained under the same conditions of cut listed for Fig. 2 except that the work material was Ti 75A. The lower curve represents data obtained near the outside surface of the bar and the top curve represents the data secured near the center of the bar. Using the equation VTn = C, the following data are derived: C n V_ n near center of work 164.097 131 near outside of work 136.1615 93.8 Since a range of results is shown for this material, the area is cross-hatched to indicate a range of performance. Figure 4 shows the results obtained for Ti 150A, which yielded the most consistent data of all the titanium materials used in this investigation. In cutting the Ti 150A there was a manifestation of tool failure on the shoulder of the work piece that was more pronounced than a similar indication onTi 75A. It was very evident in this material that the failure of a tool would produce either a work-hardening or an impregnation of tool material on the shoulder of the work piece, With the result that a subsequent cut using a newly ground tool would experience an immediate failure if the affected material was not removed with a clean-up cut. 4t

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN The equation VTn = C for the Ti 150A gives the following results: V1 T = V2 2 V2 \1 v2 80 4> 70 \83 1.143 = 566n n = 0.77 70 fpm x 4.7077 = C 70 x 1.127 = C C = 79 fpm for 1 minute tool life V10 10.077 = 79 V10 79. 79 o = lo.077 1.194 V10 = 66.1 fpm for 10 minute tool life Figure 5 indicates a narrow range of cutting speeds for a given tool life and a spread of data between the curves that have been drawn to represent boundary conditions of the RC 130B cutting speed vs tool life curves. The data covers a range represented by parallel boundaries. The equation VTn = C for RC 130B indicates the following results: C n Vlo high boundary 45.6.044 41.3 low boundary 39.4.044 35 The variation that occurs in V10 is of the order of a 16 per cent increase, whereas the variation in V10 for the Ti 75A is a 39 per cent increase.'~ ^ ~'~~~~~~~~~

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN TEST CONDITIONS Machine Tool The machine used in these tests is a 32 inch Gould and Eberhardt Industrial Shaper, shown in Fig 6. It is considered a heavy-duty type of machine. In the preliminary work done with the titanium work materials, it was found necessary to check the tightness of all gibs, ways, and clamps. Rigidity in the machine setup is of utmost importance in the successful machining of these materials. In the early stages of this investigation, considerable difficulty was encountered in machining the 130B and 150A, as compared to the cutting of most other materials, i.e., steel, cast iron, etc. A conditioning of the machine to a level of reasonable tightness and reduction of tool overhang aided in eliminating the difficulties encountered in the preliminary tests. Cutting Tools The tools used in these tests were Firth Sterling (Blue Chip) 18-4-1 high-speed-steel 1/2 inch square, tool bits. The grinding of the tools was performed on a Cincinnati No. 2 tool and cutter grinder with 38A 46J 5VBE wheels for roughing cuts and subsequently finished on a Pratt and Whitney Keller-cutter grinder equipped with a special tool-holding fixture. The signature of 0~ back rake, 28~ side rake, 6~ end relief, 60 side relief, 6~ end cutting edge angle, 150 side cutting edge angle, and 0.010-inch nose radius was selected on the basis of results obtained from the single-point tool tests in turning. Derivation of Maximum Velocity Figure 7 shows a diagram of the crank-arm and bull gear mechanism in the shaper and the critical dimensions affecting the velocity at the middle of the stroke. The maximum velocity was derived as follows: For stroke lengths of 9 to 16 inches used in tests: H = 18.75 inches (measured value)..........

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN L = 34.8 inches (measured value). D = diameter of contact circle of crank arm and bull gear. 0 = angle defined by centerline and position of crank arm for a given length of stroke. sin = S/ = S L 2L also S D S D.. --- = - or = - 2L 2H L 2H V- i= r Dn, where n = rpm of bull gear (measured value), 12 and Vmax = V1 + D/ fpm at center of stroke. The stroke of the ramcarrying the tool head. was positioned in each setup, so the cut was exactly centered on the work. Determination of Cutting Time A Sanborn 2-channel recording oscillograph with a time recording attachment was used to determine the precise amount of time of tool contact in ratio to the total time per stroke. An electrical circuit was made to react to tool contact by insulating the work piece from the vise and connecting lead-in wires to the tool and the work piece. A recording of time in cycles per second was indicated for the total stroke and the cutting phase of the stroke. It was found that a range of 20.5 per cent to 38.4 per cent, representing the ratio of contact time to total time per stroke, could be used in determining the actual cutting time in strokes varying in length from 9 to 16 inches on a piece of metal 8 inches long. Test Procedure All work pieces were squared to the following dimensions prior to testing: 2 inches thick by 4 inches wide by 8 inches long. All machine setup conditions remained constant during the tests except the cutting speed. Tool failure was determined by recording tool wear, as measured on a Binocular microscope equipped with a Filar lens. The measurements of tool wear were made at given intervals of time until the wear land was approximately 0.030 inch wide. Under this condition of 0.030-inch flank wear, the useful tool life expired. A flank wear of 0.030 inch is generally accepted as a practical 7

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN limit for tool wear where total breakdown failure does not occur at a smaller value of tool wear. The position and overhang of the tool in the tool holder was carefully gaged after each inspection in the microscope. Time of the tests was measured by a stop watch to an accuracy of 1/100 minute. CONCLUSIONS 1. The machining of Ti 75A, RC 130B, and Ti 150A has been successfully performed with single-point tools in a shaper. The dependence of tool life on cutting speed is orderly and predictable. 2. The results obtained in these tests indicate a reasonable degree of similarity in performance as compared to the single-point tool turning of these materials. 3. The speeds used for a given tool life favor the Ti 75A over the Ti 150A and the RC 130B. 4. The slopes of the tool life lines obtained in these tests favor the alloy materials as compared to the commercially pure Ti 75A titanium. 5. Results of the cutting speed, tool life tests with HSS tools, under the conditions of cut used for this report, indicate the following speed ranges for a tool life (actual cutting time) of 1-40 minutes or total elapsed time of 2.6 to 195 minutes depending on length of stroke: Ti 75A, 76 to 160 fpm Ti 150A, 60 to 79 fpm RC 130B, 34 to 45 fpm. 6. Maximum rigidity in the machine, cutting tool, and work-holding device is a necessity in the successful machining of the titanium materials covered in this report. 8

32" G E SHAPER RAM \''/~-__ -Vo I I L ARM ONcHES- VISE \ X \ z.___ V, \, l l WORK PIECE: OOL L- ARM LENGTH \ A \' (34.8 INCHES) \ \ D- DIAMETER OFCIRCLE- \ / PATH CONTACT OF / ARM BULLGEAR \ / VI- VELOCITY ONCIRCLE \ H </ OF-D- DIAMETER U L \BULL TABLE Vob ZERO VELOCITY (END \ ^ I GEAR OF STROKE) VMHA= MAXIMUM VELOC \ (tENER OF STROKE) FiG. 7

~~~~~~~~~~~~~~~~~~~':!r 0:I:' Fi /TV~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~'''I _J /C? k'~.:f _,, ~~~~B~.

SHAPING CUTTING SPEED -TOOL LIFE 4 300 00 15a: Il W 10 6 Lo 2.0 3.0 l..0 120 0~20.0 40.0 60.0 TOOL LIFE-MINUTES ACTUAL CUTTING TIME IG. 5

SHAPING CUTTING SPEED —TOOL LIFE 400 -. --- 30 01 100 1111-_ 0: 0 IL I 50__ __ _ 150, 30.__________________.6 1. 2.0 3.0 5.0 1o0. 0 20. 40.0 0.0 TOOL LIFE-MINUTES ACTUAL CUTTING TIME FI-. 4

SHAPING CUTTING SPEED-TOOL LIFE 400m K 300. 206 30n__________p~__________________,~~, 0: 0 0.6 1.0 2.0 3.0 5.0 10.0 20.0 40.0 60.0 TOOL LIFE-MINUTES ACTUAL CUTTING TIME FIG.

SHAPING CUTTING SPEED-TOOL LIFE 400 300' _ __p______ 200-__-________ S90AE. 1045 0 I 50 _ 30 ___ __ ________________________ _____________^____.6 1.0 2.0 3.0 5.0 10.0 20.0 40.0 60. TOOL LIFE -MINUTES ACTUAL CUTTING TIME FIG. 2

SHAPING CUTTING SPEED-TOOL LIFE 40 a300. ___ 200,1.~2.0 3.0 5.0 ~~510.0 20.0 40.0 60.0 TOOL LIFE-MINUTES ACTUAL CUTTING TIME I I I I -TI. 150 A RC. 130 B ~ 1.0 2.0 3.0 5.0 I0.0 20.0 40.0 60.0 TOOL LIFE —MINUTES ACTUAL CUTTING TIME Fla. I