Official Luthiers Forum!

Hi guys,

I'm trying to spend some time with my lonely CNC machine.

It's been slow going with the volume of hand work, but I'm beginning to learn!!!

Anyone care to share their method of cutting shell on their machine?

Are you misting water on the shell/ cutting bit,(rust?), or some other lube?

How do you keep the mess down?

Are you gluing the shell to a sacraficial board?

Thanks!
Paul

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Paul Bordeaux
http://www.bordeauxinlay.com

Hey Paul,
I've cut shell with a cnc once before and just used compress air to blow the dust off of the cutter.
I glued the shell to some MDF and to hold it, just used titebond to hold down, which is why I didn't use a liquid coolant I was afraid it would let go during cutting.
Also you might not want to take more than about 1x the diameter of the cutter as far as depth goes, but I might be wrong, but I broke my first cutter right away. That was a 1/32 Dia.
Good luck and keep us posted.
Did I mention how much I like the fingerboard you did for me

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Jim Watts
http://jameswattsguitars.com

Hi Paul - Good to hear you're cutting away !

I glue shell and abalam sheets with Elmers to 1/4" hardboard; full coverage on the glue. When I'm done I throw it in a bucket of hot soapy tap water for a few hours and peel the parts off the board. I've given up trying to use double-stick carpet tape because it either squirms under cutting pressure or the parts are nearly impossible to remove. Titebond takes longer to dissolve than Elmers but it works fine. Use that old bottle of something you won't use on wood anymore.

I place my dust collector hose close to the work or stand there with the shopvac. I don't use any coolant. I do have my air filter going and wear a mask.

I use a two pass cut strategy on both the shell and inlays pockets which gives me cleaner edges especially with abalam. First 15-20ipm (could probably go faster) climb milling (CW) then 40-50ipm conventional (CCW) to clean it up. In Onecnc the direction that you select the chain determines the cut direction and remember to watch what side of your chain your arrow is on since that selects inside or outside for a pocket or profile. Since they've added all that finish cut stuff to XR2 I think both passes can be done in one toolpath.

Let me know if there's anything else I can help with.

I know at Taylor they use air turbine spindles to get extremely high RPMs when they cut shell and maybe for the inlay pockets as well.

What sort of machine are you using, Rand?

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Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

[QUOTE=Jim_W] Hey Paul,

Did I mention how much I like the fingerboard you did for me [/QUOTE]
Yes, thanks Jim. Thanks for the advise too!

Hey Rand, I was hoping you would reply;

Hey gang, Rand gave me ton's of advice over at the cnczone forum before I purchased a machine.
Thank you, Rand

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Paul Bordeaux
http://www.bordeauxinlay.com

Hey Paul, I'm certainly no expert on this stuff but happy to share my experiences. I'm using an electric spindle at 18K and its got lots of power so I go to full depth + .005 margin (.065) in one cut at a slow feed with a 1/32 bit. You'll have to figure out what works best with your spindle and maybe use a rough depths (of cut) setting as Jim suggests and increase that or feed. I had started out going half (.035) depth of cut and noticed I didn't really need to be doing that. If you get fuzzy edges on abalam I suggest using leave for finish setting of .005 or .010 for the first CW pass and then clean that up with 0 LFF on the fast finish pass. You may find that with your spindle you don't need a second pass at all.