[How-To] Central Machinery 9x20 Lathe

The backplate is iron, and it will cut easily without lubrication. The chips will be crumbs, not chips like steel. I'd go medium-slow.
 
Sounds like a good starting point...

Because the cast iron sort of crumbles when cutting, the pieces are small and fling off. You may need to fashion a shield of some sort. And wear a smock...
 
Seems the case. I have been warned by many. I was thinking of having someone hold a shop vac near the cutter. See what happens.
 
For a super easy, and easy to remember RPM calculation for HSS tooling I use the following:

SFM - Surface feet per minute, or the distance the circumference of the cutter (drill bits & end mills) should move in one minute - or the distance the OD of the part should move in a minute on a lathe.
Aluminum & plastic 250 SFM
Mild steel 125 SFM
Hard steel 65 SFM

RPM = (SFM * 12) / Pi*D (convert the SFM to inches and divide by the circumference of the bit/workpiece)
But to simplify, pretend Pi = 3. Cancel the 3 and 12 to change the formula to:

RPM = (SFM * 4) / D

So, a 1 inch cutter (or workpiece in a lathe) cutting aluminum = 250*4/1 or 1,000 RPM

0.25" cutter in steel = 125*4 / .25 = 500/.25 = 2,000 RPM

It's not perfect, but it'll get you in the ballpark. But for cast iron I'm not sure what SFM to use. Probably 125, but I never use the stuff.
 
Last edited:
Wow, thanks for all that info. Still trying to digest it all and grow some courage to cut the plate. Might tackle it Saturday.
 
You must log in or register to reply here.
Back
Top