well, my run of no broken bits ended after 28 months!

[Ajcoholic]

Today I was cutting some 1/2" thick G10 composite sheet. For those unfamiliar with the stuff, it is a very heavy & dense epoxy/glass phenolic.

I have cut a lot of 1/8" in the past and some 1/4" for hobby parts (model airplane and helicopter frames, etc).

To cut the 1/2" stock, I figured after 3 broken 1/4" carbide end mills that I had to both use low RPM and a lower feed (I think I settled on 10,000 rpm and about 60 ipm feed for a 2 flute spiral Onsrud carbide).

I have cut so much wood (solids and ply) in the past 2 years and 4 months without even coming close to a broken bit. 5 minutes trying to cut a 24" by 24" sheet of this stuff and I'm back to newbie-ville! :D

[Brady Watson]

That's wicked stuff on tools. Very abrasive. I'd use a diamond coated bit for that.

-B

[Burkhardt]

That's wicked stuff on tools. Very abrasive. I'd use a diamond coated bit for that.

-B

Not just wicked on the tools. Nasty dust for the machine and your skin as well. Not mentioning breathing it. Where I work we buy tons of printed circuit board assemblies and our contract manufacturers (we still buy local) mill and drill that stuff all day long at high speed. They have very specialized machines that move so fast you can barely see it but sometimes I have to check out what bits and machining parameters they use.

[Ajcoholic]

That's wicked stuff on tools. Very abrasive. I'd use a diamond coated bit for that.

-B

Well I broke a few used carbide end mills (ones I had previously used on solid surfacing) that were $8 Onsrud specials... I just needed to make that one cut to separate the 24" by 24" pc into two sections.

I appreciate how easy wood is to machine :D Even hard maple is like butter compared to that stuff.

[myxpykalix]

Well Andrew i guess you are no longer a Shopbot Virgin. :eek::(

[scottp55]

Nice to see you're human Andrew:)

[Ajcoholic]

Nice to see you're human Andrew:)

You have seen my 8 incra hold down clamps, right? :D

I'm human. I just made a lot of mistakes before I got my bot.

The funny thing is the very first CNC project I did ( back in the early 1990's) was on a Wadkin moving table CNC router in college, cutting G10!!

But it was 1/8" material, I was cutting rc helicopter frames for a local hobby shop owner. That was probably the first time I was also exposed to spiral carbide router bits as well. And I didn't break any that I recall. :p

Man that was ages ago. Half my lifetime so far!

[Ajcoholic]

Well Andrew i guess you are no longer a Shopbot Virgin. :eek::(

Nope. But until I snap my carbide 5/8" end mill off I'll say I'm not pushing the machine hard enough. :D

[myxpykalix]

You haven't pushed it hard enough till you have buried a 1/2" endmill in the table and it doesn't stop until it blows the 2 fuses in your control box......:o