RPM calculations

For mild steel about 100 ft / min should be O.K, for a 1/4" drill that is about 1500 rpm

What speeds have you worked out ?

-- Jonathan

Barnes's theorem; for every foolproof device there is a fool greater than the proof.

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I was looking to find the speeds for 3.3mm and 4.1mm drills, I was coming up with speeds of around

John

Far be it for me to argue with twenty years experience, but I was quoting from the students shop reference handbook.

I generally find that with a machine ground ( new ) drill what they recommend works, but if I have resharpened a drill by hand I generally want to run a little slower.

Normally I'm to lazy to change from the pillar drills bottom speed of 500 which is defiantly as fast as I want to run a 1/2" drill in 316 stainless steel :-( ...... I'm looking for a drill that will run a lot slower, as I have to use the mill to work with hole saws at present.

Jonathan

Barnes's theorem; for every foolproof device there is a fool greater than the proof.

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Your figures are right - 2366 rpm at 11.8ipm feed for 4.1mm - 2940 14.7ipm for 3.3mm

Triple those for Carbide drills.

Those figures are from Cimco's tables. They are for coolant and maximum speed, not taking into account tool wear.

There's a good article and tables here

-- Steve Blackmore

Thanks everyone, thats all I wanted to know. I did ask others at work before posting here, but nobody knew the correct speeds, the cnc guys tended to run at a higher rpm, but generally on the manual machines people run similar speeds to me. I can't remember being taught to run anything at specific speeds, but personally find that higher rpm = more drill wear and more squeeling.

John

Hi Formular you need for imperial measurements is 12 x cutting speed of material, divided by PI x dia of work or cutter, divide answer by number of teeth on cutter. Hope this helps, Cheers Keith