I am trying to understand a little better, how to drill stuff with CNC.
My current approach amounts to "winging it" and deciding something like "it oughta be good enough at 2 IPM".
Well, I think that I can do better than that.
I looked and have not found a decent drilling calculator.
My feeling is that the drilling feed rate in any given material is calculated as inches per revolution, and IPR is proportional to drill diameter.
Does anyone know of some good tables for this sort of thing?
Other way 'round. You start with the recommended speed in SFM (surface feet per minute at the drill diameter) to get the RPM, then the feed drops out from the inches per revolution feed rate.
Here's one, but there are lots:-
Best regards, Spehro Pefhany
-- Some people hear voices. Some see invisible people. Others have no imagination whatsoever.
I go by looks. As long as I'm getting nice looking chips or spirals without a lot of coloration indicating high temperature, I'll settle for a speed that cuts and doesn't have me changing bits frequently.
I sort of do the same thing, too. With a manual mill, the operator is pushing on the quill by hand and the feedrate is easy to change. With a CNC, the rate is in the program. It may be easier to break the drill in case of a mistake.
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This is why essentially all commercial CNC controls have nice simple override knobs for feed rate and usually spindle RPM, so the operator can readily fine tune the operation to match the actual cutting conditions interactively without having to recode the program.
2% dia per rev
That seems easy enough! I can remember that. Thanks
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