What is the Formula?

[widgitmaster]

What is the formula for calculating a bridgeport / lathe feedrate in Inches per Minute, when all you know is the RPM & .200/revolution of the leadscrew?

My bridgeport has a simple powerfeed on the x-axis, and no indication or divisions of how fast its moving? By experience, I can see & feel the feedrates, but have no idea what they really are!

IPM=RPM*.200 ?

Eric

[Gads]

Hi I dont know if this is what your looking for but if you know the rpm and the leadscrew pitch you should just have to multiply the rpm x pitch
100rpm x .200 = 20ipm etc..

do you know what rpm the power feed is turning? if this is what you are looking for you should be able to mark the other end of your screw/handwheel etc.. and use a stop watch to and count the revs if possible.

[widgitmaster]

I have one of those old Starrett tachometers, that fits in the center of the rotating shaft. So the RPM would be a known value.
Eric

[Gads]

So if you know the rpm and the pitch you can calculate as described earlier rpm x pitch = ipm.

you can also use that info to find your chip load if you needed.
ipm / rpm (spindle) / # of flutes

20ipm / 2000rpm (spindle) / 2 flutes = .005 chip per flute

[widgitmaster]

Thanks,
I know these are basic, but as an old manual machinist, feedrates were never important! So I guess I need to learn new tricks!

Thanks,
Eric

[lakeside]

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[ViperTX]

widigitmaster....what you first stated is correct. IPM = RPM * .200 in/revolution