CS-1 Feeds and Speeds Production on drills, mills, lathes, grinders, and other machine tools depends on the rate of relative motion between the cutter or grinding wheel and the workpiece. Gears roll together, there is no relative rotation speed difference where teeth mesh. There must be a difference for cutting to take place. The amount of this difference is called SFM or SFPM (Surface Feet Per Minute). When the workpiece or tool, or both, rotate, the difference in speeds at the contacting surface can be calculated from the RPM (Revolutions Per Minute). Because of the many variables in equipment and tool condition, actual speeds may vary. Speeds and Feeds should be as high as practical in order to provide an adequate rate of Production. Practical limits are set by finish requirements, power available, rigidity of the workpiece, the machine tool, and by expected tool life. When the finish is satisfactory, power is sufficient, no present threat of distortion, no burning or breaking, and the tool life is satisfactory, then the speed and feed are not too high. Whenever chatter indicates an incorrect speed or feed, higher as well as lower speeds or feeds should be tried. In feed is the name given to feed that is in the plane of rotation of the cutter or workpiece on mills, lathes, and grinders, into the work. The greater the In Feed, the greater the depth of cut. On drills and surface grinders In Feed is called Down-feed because of it's direction. Cross - Feed is feed perpendicular to the plane of rotation of the workpiece, cutter, or grinding wheel. On a lathe it is set in a number of thousands of an inch per revolution of the workpiece. On surface grinders and mills, it is made by movement of the saddle, perpendicular to the table movement, but in the same X, Y, plane. Cross feed on all machines is mainly limited by tool life and surface finish. Cross feed should be as high as finish requirements and reasonable tool life will allow. The forces at work in machining are by far highest in those interactions due to relative rotation. In feed and cross feed are also factors, but secondary ones. Once appropriate SFPM has been established for the machine tool, and workpiece, correct in feed and cross feed can quickly be made. Turning SFPM The diameter of a round piece of work is the largest measurement perpendicular to the axis across the work. In order to find the distance that passes the tool point in one revolution, the diameter is multiplied by 3.14. This distance is called the circumference. The diameter is given in inches, therefore the circumference is in inches.
(Recommended Surface Feet Per Minute) CS-2 High Speed Steel Carbide -- Tipped Material Rough Finish Rough Finish Coolant Cast Iron 50-60 80-110 180-200 350-400 Dry Semi-Steel 40-50 65-90 140-160 250-300 Dry Malleable Iron 80-100 110-130 250-300 400-500 Soluble, Sulphurized Mineral Oil Cast Steel 45-60 70-90 150-180 200-250 Soluble, Sulphurized, Mineral or Mineral Lard Oil Copper 100-150 150-200 600 1000 Soluble, Sulphurized, or Mineral Lard Oil Brass 200-300 200-300 600-1000 600-1000 Dry Bronze 100-150 150-180 600 1000 Soluble, Sulphurized, or Mineral Lard Oil Aluminum 400 700 800 1000 Soluble or Sulphurized Oil Mineral Oil and Kerosene Magnesium 600-800 1000-1500 1000-1500 1000-1500 Dry, Kerosene, or Mineral Lard Oil SAE Steels 1020 60-80 60-80 300 300 Soluble, Sulphurized Course Feed Mineral, or Mineral Lard Oil 1020 100-120 100-120 450 450 " " Fine Feed 1035 75-90 90-120 250 250 " " 1050 60-80 100 200 200 " " 3150 50-60 70-90 200 200 " " 4340 40-50 60-70 200 200 Sulphurized and Mineral Oils Stainless Steel 60-80 100-120 240-300 240-300 " "
CS-3
CS-4 Definition of Cutting Speed Cutting speed is the rate at which a point on the circumference of a cylindrical workpiece passes a cutting tool. Cutting speeds are given in Feet Per Minute, while spindle speed is given in Revolutions Per Minute, thus the peripheral speed of the workpiece (speed at circumference) must be converted to Revolutions Per Minute (RPM) in order to determine the required spindle speed. The following formula is used; RPM = C.S. x 4 D Legend C.S. = Cutting Speed D = Workpiece or Cutter Dia. Example: Machine a workpiece 3/4" in diameter from Stainless Steel. 1. RPM = C.S. x 4 D 2. R.P.M. = 40 x 4.75 3. R.P.M. 160.75 4. R.P.M. = 213
For Various Diameters CS-5 The following chart revolutions are based on the formula; RPM= CS x 12 -------------------- x D Meters Per Minute 15.2 18.3 21.3 24.4 27.4 30.5 33.5 36.6 39.6 42.7 45.7 61 94.1 Feet Per Minute 50' 60' 70' 80' 90' 100' 110' 120' 130' 140' 150' 200' 300' Diameter mm Inches Revolutions Per Minute 1.6 1/16 3056 3667 4278 4889 5500 6111 6722 7334 7945 8556 9167 12229 18344 3.2 1/8 1528 1833 2139 2445 2750 3056 3361 3667 3973 4278 4584 6115 9172 4.8 3/16 1019 1222 1426 1630 1833 2037 2241 2445 2648 2852 3056 4076 6115 6.4 1/4 764 917 1070 1222 1375 1528 1681 1833 1986 2139 2292 3057 4586 7.9 5/16 611 733 856 978 1100 1222 1345 1467 1589 1711 1833 2446 3669 9.5 3/8 509 611 713 815 917 1019 1120 1222 1324 1426 1528 2038 3057 11.1 7/16 437 524 611 698 786 873 960 1048 1135 1222 1310 1747 2621 12.7 1/2 382 458 535 611 688 764 840 917 993 1070 1146 1529 2293 15.9 5/8 306 367 428 489 550 611 672 733 794 856 917 1223 1834 19.1 3/4 255 306 357 407 458 509 560 611 662 713 764 1019 1529 22.2 7/8 218 262 306 349 393 436 480 524 568 611 655 874 1310 25.4 1.0 191 229 267 306 344 382 420 458 497 535 573 764 1146 28.6 1 1/8 170 204 238 272 306 340 373 407 441 475 509 679 1019 31.8 1 1/4 153 183 214 244 275 306 336 367 397 428 458 612 918 34.9 1 3/8 139 167 194 222 250 278 306 333 361 389 417 556 834 38.1 1 1/2 127 153 178 204 229 255 280 306 331 357 382 510 765 41.3 1 5/8 117 141 165 188 212 235 259 282 306 329 353 470 705 44.5 1 3/4 109 131 153 175 196 218 240 262 284 306 327 436 654 47.6 1 7/8 102 122 143 163 183 204 224 244 265 285 306 408 612 50.8 2.0 95 115 134 153 172 191 210 229 248 267 287 382 573 57.2 2 1/4 85 102 119 136 153 170 187 204 221 238 255 340 510 63.5 2 1/2 76 92 107 122 137 153 168 183 199 214 229 306 459 69.9 2 3/4 69 83 97 111 125 139 153 167 181 194 208 278 417 76.2 3.0 64 76 89 102 115 127 140 153 166 178 191 254 381
CS-6 Cutting, Rim, and Surface Speed Formula's C.S. = Cutting Speed R.S. = Rim Speed S.S. = Surface Speed = 3.1416 R.P.M. = Revolutions Per Minute D = Diameter of Workpiece or Milling Cutter C.S. = D x RPM RPM = CS x 12 12 D R.S. = D x RPM RPM = RS x 12 12 D S.S = D x RPM RPM = SS x 12 12 D D = C.S. x 12 RPM x
(Calculating -- RPM's) CS-7 Calculate the revolutions per minute for the following machining jobs and select an available machine tool RPM from the list. (Please calculate both Rough and Finish Cuts) Machine tool revolutions per minute available; 48 68 88 116 140 180 225 260 300 385 492 560 665 790 928 1087 1492 2400 3100 4300 6000 Tool Work Work Recommended RPM Material Material Dia. SFPM From above list Carbide Cast Iron 2.00 HSS StainlessSteel 1.500 HSS Malleable 1/2" Iron Carbide Copper 5/8" Carbide Brass 1.300 HSS Bronze 7/8" Carbide Aluminum 2.25 HSS Magnesium 2.250 HSS 1050 c.s. 1.250 Rough Finish Rough Finish
CS-7 Q1 Cutting Speed Quiz 1. How many RPM's are required to turn a gear blank 4.5" in diameter at a cutting speed of 42 FPM? 2. A piece of Tool Steel, 3/4" in diameter is turned in a lathe. How many RPM's are necessary if the cutting speed is 30 FPM? 3. If turning a Cast Iron Pulley, 14" in diameter. what RPM's are necessary using a cutting speed of 46 FPM? 4. It is desired to turn a 3/8" diameter screw at 70 FPM. Then a thread is to be chased at 20 FPM. Find the turning RPM and the threading RPM. 6. Find the Revolutions Per Minute for the following; (A) Drill a 3/16" diameter hole in brass. (B) Bore a 2 1/4" hole in aluminum. (C) Mill the surface of low carbon steel with a 3/4" end mill. (D) Turn a 2" diameter workpiece made from cast iron material. (E) Chase a 1/2-13 thread on stainless steel using a single point threading tool.