Here's a link I posted a year ago explaining the SFM.
I'll copy and paste it here for easy reference
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I actually just wanted to bring this thread back to life as I always read so many good tips and talks about the polishing and buffing.
It seems I never hear talk of the 'Surface Feet Per Minute' or SFM. If followed properly you can calculate the ideal dia of the wheel to be used for a particular material.
SFM relates to the distance in feet that the workpiece surface or cutting edge travels in one minute.
There's a simple math formula for this.
SFM = 1/4 of the wheels's diameter * arbor speed.
The ideal SFM for Stainless Steel is around 8000 sf/min. Plastics go from 1200 to 4000 sf/min.
When buffing with speeds over 5000 sf/min you get into 'molecule migration' territory. In short, molecules start to move around and this is what cause the heat generation which can become to excessive.
For example If you are using a 3600rpm polisher, by using a 10" wheel = 1/4 of 10 inches = 2.5 inches * 3600 = 9000 SFM.
A little high. It could pass but by chosing an 8" wheel it becomes (2 inches x 3600rpm) 7200 SFM. It's lower but it could work too.
Now you con easily use an 8" wheel on an 1800 RPM polisher = equals 3600 SFM. It's far from the 8000 needed for steel. Difference is it will take you much much longer to get the desired result but at a safer usage.
Off course no one says you need to follow this procedure but it can give you an easy and rough estimate as to what wheel to use.
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I have an 1100, 1850 and 3600 RPM and use them all.