Official Luthiers Forum!

Well, I am supposed to pick up my CNC router today. I'm excited.

I have a few basic questions about cutting abalam on CNC:

1) How do you secure the abalam while it is being cut? I doubt double-stick tape is going to hold these small pieces securely enough to get precise cuts.

2) Can someone recommend some specific end mills for cutting abalam? Manufacturer, size, supplier, etc.

3) How deep are your passes when you cut abalam?

4) Feed rate? My spindle has a max speed of 25k.

5) How thin of piece can you cut before you get problems? I don't mean the thickness of the abalam blanks; I mean how wide does the piece need to be in order to avoid having it shatter while cutting. I would like to make some very fine lines for a pinstripe-like inlay, and I'm wondering how fine the lines can be before I'll get problems.

Thanks! Any other insights you can offer would also be appreciated!

Congrats on the new machine. What did you get ?

1. Glue it to a piece of hardboard (Masonite). HHG, white/yellow, CA, elmers school glue works well. Think about how you want the pieces oriented etc, maybe draw a grid on the hardboard because you'll probably need to rezero for each piece etc. When done dump the hardboard in a bucket of warm tap water for a few hours or flood with acetone for CA.

2. Anything the right size will work on abalam. Precisebits makes cutters for pearl and their fretslot cutters work fine too. I use 1/32 and 1/16 cutters from Micro100 or Atrax but bought a bunch of fretslot bits and have one that I use just for pearl some. Abalam is easier than pearl. MSC is good for the generic bits but check prices and there are some decent ebay sellers like drillman.

3. I go to .002z on a roughing pass at 12 leaving .005 on the profile and then a finishing pass to 0z and to size. You'll want to experiment with how you want to do it. High RPM is best.

You'll have to experiment around with everything else. Start with wood, work up to pearl. Make inlay pockets in scrap, make inlays out of wood scrap cut into veneers or acrylic. New machine ? cut circles and squares make sure they fit the pockets, move onto tougher stuff.

Have fun

Thanks, RandK! That's great advice.

I bought the Laguna IQ Pro. It's sitting in the back of my truck because I realize it's going to take six guys to lift it out of there. I'm very excited to start playing with it.

Thanks again,
Kelby.

1- HHG on hardboard (HDF). I drop the pieces in a bowl of water upside down and microwave it until they fall off.

2,3,4- PreciseBits are the best, and they have speeds and feeds on their website

5- I've cut dots that were 0.04" around and maybe smaller from 0.05" abalam, and line widths below 0.014". Thinner lines are possible, but then it gets really expensive. It's harder to handle the pieces after they've been cut without breaking them than it is to cut the thin lines.

_________________
Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

Great stuff, Bob. Thanks!

As a follow-up, tonight I was able to test cut a small inlay pattern in some veneer. I'm attaching an image of the pattern I was trying to cut. The lines are .015" wide. The machine cut nicely, but the .055" thick veneer was too fragile and the narrow lines bent and broke in some spots during cutting. Am I likely to have similar problems with shell, or is the shell going to be sufficiently more ridged than the veneer to be able to handle being cut into this narrow of a piece? Do I need to thicken the lines

I've cut .016 wide lines in MOP before without any problem. Should be strong enough. Wood veneer is one of the more difficult things to cut well with a CNC, mostly because it's really hard to hold down in a way that you won't damage it upon removal.

Something to consider though: if your smallest bit is .015 and you're cutting a .015 pocket, your CAM software might not realize that it can fit the tool down into the pocket, even if you specify a pocket clearance. If you have this problem, try thickening the line to .016 and it should start working.

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http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com

I frequently use the "permanent" grade of double stick tape to hold shell when I'm making a run of a bunch of the same inlay so that I don't end up having to re locate my zero point or move my masonite around between cuts to put a new piece of shell in place. The problem with this method is not that the tape isn't strong enough--it's that the tape won't let go easily enough for delicate shapes without breaking. I glue the shell for that kind of work. But for little scalloped diamonds, stars, man in the moon and other traditional banjo inlays (the ones without little tendrils and such), the tape is a real time saver for me.

I use the precise bits shell cutters and either .050 or .060 solid shell for the most part. Feed rate usually 20 to 40 ips and spindle at 18,000 (the max my spindle will do).

Dave