My nifty little tapping guide says 10-15 SFpM for 400 stainless.
A place I used to work had a different slant on things...
Threads per Inch times 10 equals RPM. (24 TPI = 240 rpm)
Their logic behind this was pretty convincing... The pitch determines the actual size (surface area) of the thread; a smaller thread (higher tpi) can run faster than a larger thread (lower tpi).
This really suprised me at how well it worked, but I can't remember for certain if it was 300 or 400 stainless.
But the nifty tapping guide has never failed me! |