Profile bit for thick hard wood.

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Larry Cessna
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Profile bit for thick hard wood.

Post by Larry Cessna »

I am cutting out guitar bodies from 1.75 inch thick walnut. I cut the profile with 8 passes and then a full depth finishing pass at about .01 offset. I am getting a lot of chatter with my bit. I need a bit to cut at least 1.75 with one finishing pass. What bit do you recommend and the speed and feed for in. Thanks

potzmannwoodshop
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Re: Profile bit for thick hard wood.

Post by potzmannwoodshop »

Chatter is as much about the bit as it is about your machine, or your feeds and speeds. If your machine isnt rigid enough you will get chatter no matter what, if you part isnt held well enough it will chatter, if your feed speed is too high you will have chatter.

The bit is likely not the problem.

For anything thick I usually reach for my 1/2" endmill or the 3/4" endmill. But I have used a 1/4" to make a 1.5" cut in solid wood where a 1/2" wouldn't fit. So Im thinking it isnt the bit.

Tell us about your machine, BTW 8 passes seems like too many, even with a 1/4" bit that should only be at most 4, maybe 5

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highpockets
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Re: Profile bit for thick hard wood.

Post by highpockets »

Are you using a Conventional or Climb cut?
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Larry Cessna
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Re: Profile bit for thick hard wood.

Post by Larry Cessna »

I have a laguna swift with 3hp water cooled spindle. I do not get chatter with when I use shorter .25 end mill bits. I tried a straight (.5) 4 inch with a 2 inch cutting surface but it chattered and made a very rough cut. I will buy a 1/2 inch with an up cut and 2 inch cut 4 inch long. they are about $100 on tools today. What do you think a good speed and feed for this would be. I run 18000 @ 180 ipm at .2 depth with a .25 end mill some time I slow the speed if its to loud.

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dealguy11
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Re: Profile bit for thick hard wood.

Post by dealguy11 »

The climb vs. conventional question is relevant, and the "right" answer depends on material and your machine. For example, on my machine I get a better cutout in hardwood with a conventional toolpath, but the opposite for plastics. I've heard other people have different experiences with their machines, so you need to experiment to see what works.
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ger21
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Re: Profile bit for thick hard wood.

Post by ger21 »

Drop your RPM to about 13,000-14,000, and keep the feedrate the same.

I've been cutting 2" oak door components, and use this method.
Start with a downcut spiral, and make 3 passes of about .33", leaving .02 for a clean up pass. Then make the 4th cut a finish pass at about 1.2" deep. The bit has a 1.25" flute length.
300-350ipm @ 15,000 rpm, but I have a 15HP spindle.

Then switch to an upcut spiral, and cut at about 200ipm, 1/4" per pass, to final size.
Gerry - http://www.thecncwoodworker.com

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Re: Profile bit for thick hard wood.

Post by ger21 »

And I agree, I always conventional cut wood, unless it's going to blow apart. Only then will I climb cut. This is usually when cutting a rabbet with the grain.
Gerry - http://www.thecncwoodworker.com

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