Hi All,

Must be a senior moment but I am stumped.

1/2" dia. two flute carbide cutting SFM 850, cut per flute 0.002" it
calculates out to around 6500rpm at 26-IPM

1/2" dia. two flute HSS cutting SFM 425, cut per flute 0.002" it
calculates out to around 3250rpm at 13-IPM

No surprises there. However, I don't like running the the spindle at
top speed (3000rpm) so I tried to figure the IPM for say 2000rpm. My
thinking for carbide...

6500 / 2000 = 3.25
26 / 3.25 = 8 IPM at 2000rpm

OK, still so far so good, but using that same thinking with HSS

3250 / 2000 = 1.625
13 / 1.625 = 8 IPM at 2000rpm HUH???????????????????

Where am I going wrong here? The HSS should be half the carbide IPM.

Dave