Calculating R.P.M.’s
| Part Diameter | Cast Iron, Brass, Stainless |
| Steel |
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| Aluminum |
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| S.F.P.M. |
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| 40 | 50 | 60 | 70 | 80 | 90 | 100 | 110 | 120 |
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0.016 ' |
| 9779 | 12224 | 14669 | 17114 | 19558 | 22003 | 24448 | 26893 | 29338 | ||
0.031 ' |
| 4890 | 6112 | 7334 | 8557 | 9779 | 11002 | 12224 | 13446 | 14669 | ||
0.062 ' |
| 2445 | 3056 | 3667 | 4278 | 4889 | 5500 | 6112 | 6723 | 7333 | ||
0.125 ' |
| 1222 | 1528 | 1833 | 2139 | 2445 | 2750 | 3056 | 3361 | 3667 | ||
0.187 ' |
| 815 | 1019 | 1222 | 1426 | 1630 | 1833 | 2037 | 2241 | 2445 | ||
0.250 ' |
| 611 | 764 | 917 | 1070 | 1222 | 1375 | 1528 | 1681 | 1833 | ||
0.312 ' |
| 489 | 611 | 733 | 856 | 978 | 1100 | 1222 | 1345 | 1467 | ||
0.375 ' |
| 407 | 509 | 611 | 713 | 815 | 917 | 1019 | 1120 | 1222 | ||
0.437 ' |
| 349 | 437 | 524 | 611 | 698 | 786 | 876 | 960 | 1048 | ||
0.500 ' |
| 306 | 382 | 458 | 535 | 611 | 688 | 764 | 840 | 917 | ||
0.625 ' |
| 244 | 306 | 367 | 428 | 489 | 550 | 611 | 672 | 733 | ||
0.75 ' |
| 204 | 255 | 306 | 357 | 407 | 458 | 509 | 560 | 611 | ||
0.875 ' |
| 175 | 218 | 262 | 306 | 349 | 393 | 473 | 480 | 524 | ||
| 1.0 ' |
|
| 153 | 191 | 229 | 267 | 306 | 344 | 382 | 420 | 458 |
1.125' |
| 136 | 170 | 204 | 238 | 272 | 306 | 340 | 373 | 407 | ||
1.25 ' |
| 122 | 153 | 183 | 214 | 244 | 275 | 306 | 336 | 367 | ||
1.375 ' |
| 111 | 139 | 167 | 194 | 222 | 250 | 278 | 306 | 333 | ||
1.5 ' |
|
| 102 | 127 | 153 | 178 | 204 | 229 | 255 | 2~0 | 306 | |
1.625 ' |
| 91 | 118 | 141 | 165 | 188 | 212 | 235 | 259 | 282 | ||
1.75 ' |
| 87 | 109 | 131 | 153 | 175 | 196 | 218 | 246 | 262 | ||
1.875 ' |
| 82 | 102 | 122 | 143 | 163 | 183 | 204 | 224 | 244 | ||
2.0 ' |
|
| 76 | 96 | 115 | 134 | 153 | 172 | 191 | 210 | 229 | |
2.25 ' |
| 68 | 85 | 102 | 119 | 136 | 153 | 170 | 187 | 204 | ||
2.5 ' |
|
| 61 | 76 | 92 | 107 | 122 | 138 | 153 | 168 | 183 | |
2.75 ' |
| 56 | 70 | 83 | 97 | 111 | 125 | 139 | 153 | 167 | ||
3.0 ' |
|
| 51 | 64 | 76 | 89 | 102 | 115 | 127 | 140 | 153 | |
3.25 ' |
| 47 | 55 | 71 | 82 | 94 | 106 | 118 | 129 | 141 | ||
3.5 ' |
|
| 44 | 59 | 66 | 76 | 87 | 98 | 109 | 126 | 131 | |
3.75 ' |
| 41 | 51 | 61 | 71 | 81 | 92 | 102 | 112 | 122 | ||
4.0 ' |
|
| 38 | 48 | 57 | 67 | 76 | 86 | 96 | 105 | 115 | |
4.5 ' |
|
| 34 | 42 | 51 | 59 | 68 | 76 | 85 | 93 | 102 | |
5.0 ' |
|
| 31 | 38 | 46 | 54 | 61 | 69 | 76 | 84 | 92 | |
5.5 ' |
|
| 28 | 35 | 41 | 49 | 56 | 63 | 70 | 76 | 83 | |
6.0 ' |
|
| 26 | 32 | 38 | 45 | 51 | 57 | 64 | 70 | 76 | |
6.5 ' |
|
| 24 | 29 | 35 | 42 | 47 | 53 | 59 | 65 | 71 | |
7.0 ' |
|
| 22 | 27 | 33 | 38 | 44 | 49 | 55 | 60 | 66 | |
7.5 ' |
|
| 20 | 26 | 31 | 36 | 41 | 46 | 51 | 56 | 61 | |
8.0 ' |
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| 19 | 24 | 29 | 33 | 38 | 43 | 48 | 53 | 57 | |
Example: 1'' diameter steel using 80 surface feet per minute should be run at 306 r.p.m. To cal- culate r.p.m.s for diameters not listed here; multiply the surface feet per minute by the diameter of the stock and divide by 4.
G4000 9'' x 19'' Lathe |