Need some advice about tiny end mills and wood

Z

zhyla

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Sep 11, 2011
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So I've been trying to use my mini mill to cut the slots in the front of Japanese-style wa-handles for my knives. I bought a 1/16" end mill and, thinking wood is way easier to machine than metal, snapped the end mill in about half a second.

So I ordered a 2 mm end mill (slightly thicker) and super carefully cut a slot in some stabilized wood. Woot! Then I snapped it off halfway thru the next slot in a piece of ebony. Gah! It actually snapped while backtracking thru some swarf in the slot.

Is there some trick here? I'm using 4-fluted end mills and going super slow. For knuckleheaded reasons I had the RPM way low this last time (400 RPM). Next time I'm going to have it going at max speed, I think you're supposed to use high SFM for cutting wood. But it just seems like any lateral stress and the bit snaps off.
 
I've used 2 flute and 4 flute end mills in wood with success. If you ever snap an end mill and need one right away, north county tool and abrasive in San Marcos has them in a different sizes. Todd is a good dude and deals in cash or check only.
 
Drill nearly touching holes for the slot then you only have to mill the webbing between the holes.
 
1/16" is pretty darn small for an end mill - they are used with CNC a lot, but even there you've got to be super careful with shallow cuts and very control feed speed. I've tried a couple of small end mills in CNC, but tend to keep 1/8" as about the smallest I like to use.

What type of machine are you using for a 1/16" end mill?

Ken H>
 
400 RPM is a little low. 100,000 RPM would be better.
 
Must be your speed. I was just milling wa handle blade slits at .093" in stabilized african blackwood today and remarking how it was cutting like not even there. Had my RPM's at max speed and fed by hand.
 
jdm61 said:
If it was anyone other that you saying it, I would be inclined to take that as a joke. :D
Click to expand...

Well it was kind of a joke, though that is a good number. I wanted to illustrate how far out of whack 400 RPM is for a 1/16" cutter.

A wood cutting skill saw turns thousands of RPM with a large blade. 400 RPM is closer to what you'd see on a small cold saw that is two orders of magnitude larger than a 1/16" cutter.

100,000 RPM is an appropriate RPM for a 1/16" cutter in wood, though you'd have to feed it pretty quick. 20,000 RPM might be better for a slow hand feed. 400 RPM would be more appropriate with a big 10" molding cutter. In something hard. like aluminum...

It's all about the peripheral speed of the cutter and the materials cutting and being cut. In order to maintain SFM, the RPM is proportional to the diameter of the cutter. Small cutters are run faster...
 
In order of solving your problem:

In wood, turn the bit fast to cut clean. Ten thousand RPM or more if you mini-mill has that ability.
Take shallower cuts and repeat them as you go deeper.
Move the wood fast enough to prevent burning, but slow enough to not side load the thin milling bit.
 
Nathan the Machinist said:
Well it was kind of a joke, though that is a good number.
Click to expand...

Yeah I got what you were saying. I just had it stuck in my head that slower was safer.

My mill taps out at 2250 RPM. I've seen some people hang a router off the head to do wood milling. But I'll see how it does at 2250. If that doesn't work I can always pre-drill the slot as JMJones suggests.
 
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