Couple of questions about the speed and feed chart

I’ve got a couple of questions about the speed and feed chart found here:

Is this an acronym for “diameter of cutter”? Also, the value that is found in this column, are they only limited to just this size? What if, for example, I want to use .25" instead of .4" for pine wood. Do the RPM, feed, and plunge values change or do they remain the same? If not, by how much do they change?

What unit are these values in? Also, are they in measurement over time? Example: 100 mm/min?


The (") symbol is international for Inches

Feed is in Inches per Min (IPM)

Doh! :slight_smile:

Depth of cut!

To expand on Rich’s answer:

DOC == Depth of Cut

That chart is specific to 0.25" diameter endmills

The units are Imperial inches (per minute) — the curly quotes are standing in for proper double primes.

There’s a metric version here: which has been somewhat regularized — it would be great if folks would confirm that said regularization is okay and results in values which actually work.

If I have assorted endmills how would i go about getting speeds and feeds?

I have just been using these speeds and feeds for .25 and for smaller endmills, .03 dia.

Is this just a trial and error type thing?

Trial and error will work, but may break endmills and be rough on the machine.

It’s supposed to be a matter of calculation, and I’ve been trying to wrap my mind around it.

The G-Wizard calculator from Bob Warfield at CNC Cookbook seems to be the best option (and at one point in time it had a nifty integration with MeshCAM) — all of my notes / research on this is pretty much on the Materials page on the Shapeoko wiki — eventually I’ll understand it all, or at least work up some reasonable feeds and speeds for a 1/8" endmill on a Shapeoko 3.

Esp. see


thanks WillAdams!

Helpful as always :slight_smile:

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