Alan Koski (10-13-2010) provided the following table and information.
The first two columns refer to the pulleys on his mill.

OK.  Here is the chart that I have for my mill.

	            diameter (inches)
             Alloy CRS   mild  Bron  Alum  Bras
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)

For the different kinds of material (across the page) with their
recommended surface speed, I list the various rpms and settings I
can get on my mill.  The intersection of the two axes gives the
diameter of the tool (for high speed steel tools) from the formula.
I use that as a maximum.  So, from my chart, I can quickly see
which rpm to use, or what size tool to use.