Alan's speed tables

For the lathe, the table shows the diameter of workpiece this would be appropriate for.
For the mill, the table shows the diameter of end mill that should be used.

The materials are:

Alloy Steel             -  60 sfm
CRS - cold rolled steel -  80 sfm
mild steel              - 120 sfm
Bronze                  - 150 sfm
Aluminum                - 300 sfm
Brass                   - 600 sfm

Alan says:

For the lathe:

                   max diameter (inches)
            Alloy CRS   mild  Bron  Alum  Brass
set   rpm    60    80    120   150   300   600 sfm
---   ---   ----  ----  ----  ----  ----  ----
B 1    64   3.6   4.8    7.2   9.0  18    36
B 3   170   1.4   1.8    2.7   3.4   6.7  13
C 1   177   1.3   1.7    2.6   3.2   6.5  13
A 1   231   1.0   1.3    2.0   2.5   5.0  10
B 2   305   0.75  1.0    1.5   1.9   3.8   7.5
C 3   474   0.48  0.64    .97  1.2   2.4   4.8
A 3   613   0.37  0.50    .75   .93  1.9   3.7
C 2   844   0.27  0.36    .54   .68  1.4   2.7
A 2  1093   0.21  0.28    .42   .52  1.0   2.1
           d = (12 * sfm) / (pi * rpm)

For the mill:

	         max diameter (inches)
            Alloy CRS   mild  Bron  Alum  Brass
set   rpm    60    80    120   150   300   600 sfm
---   ---   ----  ----  ----  ----  ----  ----
L D    92   2.5   3.3   5.0   6.2   12.5  25
L C   153   1.5   2.0   3.0   3.7    7.5  15
L B   233   1.0   1.3   2.0   2.5    4.9   9.8
1 D   338   .68   .90   1.4   1.7    3.4   6.8
1 C   562   .41   .54    .82  1.0    2.0   4.1
2 D   651   .35   .47    .70   .88   1.8   3.5
1 B   856   .27   .36    .54   .67   1.3   2.7
2 C  1082   .21   .28    .42   .53   1.1   2.1
3 D  1178   .19   .26    .39   .49    .97  1.9
2 A  2660   .086  .11    .17   .22    .43   .86
3 B  2966   .077  .10    .15   .19    .39   .77
3 A  4790   .048  .064   .096  .12    .24   .48
	  d = (12 * sfm) / (pi * rpm)

If you run at too high an rpm you can "burn up" your tool. What that really means is the tool gets too hot (and weak) and the sharp edge wears itself dull. Since the usual tables give a whole range of rpms (most of which I don't have), I made my tables for exactly my rpms (along with the handle or belt positions), and then listed the maximum diameter of part (for the lathe) or tool (for the mill) which will give those sfms for the various materials.

I never run any machine at maximum speed - it is just too scary. I might get the lathe going at 613 rpm, but with the chuck turning that fast, it is enough. Maybe if I were using collets, I could go faster. On the other hand, on the mill, the spinning part is the tool. There I have used 1082 rpm with a 1 inch cutter on aluminum.