Conversion Chart SFM to RPM Cutter Diameter

SFM 1/8" 1/4" 3/8" 1/2" 5/8" 3/4" 7/8" 1"
50 1,527 763 509 382 305 244 218 191
60 1,832 916 611 458 366 305 262 229
70 2,137 1,069 712 534 427 356 305 267
80 2,443 1,221 814 611 489 407 349 305
90 2,748 1,374 916 687 550 458 393 344
100 3,053 1,527 1,018 763 611 509 436 382
150 4,580 2,290 1,527 1,145 916 763 654 573
200 6,107 3,053 2,036 1,527 1,221 1,018 872 763
250 7,634 3,817 2,545 1,908 1,527 1,272 1,091 954
300 9,160 4,580 3,053 2,290 1,832 1,527 1,309 1145
350 10,687 5,344 3,562 2,672 2,137 1,781 1,527 1336
400 12,214 6,107 4,071 3,053 2,443 2,036 1,745 1527
450 13,740 6,870 4,580 3,435 2,748 2,290 1,963 1718
500 15,267 7,634 5,089 3,817 3,053 2,545 2,181 1908
600 18,321 9,160 6,107 4,580 3,664 3,053 2,617 2290
700 21,374 10,687 7,125 5,344 4,275 3,562 3,053 2672
800 24,427 12,214 8,142 6,107 4,885 4,071 3,490 3053
900 27,481 13,740 9,160 6,870 5,496 4,580 3,926 3453
1000 30,534 15,267 10,178 7,634 6,107 5,089 4,362 3817
1100 33,588 16,794 11,196 8,397 6,718 5,598 4,798 4198
1200 36,641 18,321 12,214 9,160 7,328 6,107 5,234 4580
  1. Finishing is defined as a radial depth of cut 10% of the tool diameter or less.
  2. Roughing/Finishing is defined as a radial depth of cut of less than 25% of tool diameter.
  3. Roughing is defined as a radial depth of cut of 50% or more of the diameter.
  4. Feeds are based on axial depth not greater than 1-1/2 times tool diameter, if axial depth is more than 1-1/2 diameter, reduce feed by 30%.
  5. When slotting, 100% of cutting diameter engaged, reduce feed by 30%.
  6. Stub lengths, flute length equal to cutting diameter, increase feed by 20%.
  7. To convert SFM to RPM, multiply the surface footage times 3.82 and divide by the diameter. RPM=(3.82*SFM)/Diameter
  8. The above are general guidelines, actual final speeds and feeds could be higher or lower depending upon specific machining conditions.