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Who is using CNC for acoustic guitar braces and how are you holding down the stock? I have a bunch of spruce I have quartersawn and sized to my thickness needs. All are about 3/4 to 1" high and various lengths. I'd love to drop a few sticks on the table and whip out some rough shaped braces. I've been using double sided tape, but was trying to avoid using it here. I have a vacuum that I have yet to use, but I'm not sure I could even use it for bracing. Just not much stock to grab on to.

Ken

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http://www.casperguitar.com

Hold it with Vacuum. Use 1/8" bits, shallow cuts and high feed speed. Leave stock +.020" thicker than your desired thickness then stop the cut .020" shy of cutting through. Run the braces through the thickness sander to your desired thickness.

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tim...
http://www.mcknightguitars.com

What Tim said- that's how I'd do it.

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Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

Thanks Tim and Bob. Unfortunately, I thicknessed my stock months ago prior to getting the CNC. But your approach makes sense.

Ken

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http://www.casperguitar.com

Double stick tape it, then, just make sure you set your depth a little bit shallow and you can shave off that last thin bit with a piece of sandpaper. Since most people round over the tops of their braces a bit, you can also just do as Tim said above and use a spindle sander or the end of a belt sander to shave off the last 20 thou down to the top of the brace rather than cutting thickness off the whole thing.

Alternately, you can hold it down to a piece of plastic or metal with two or three -tiny- drops of CA (and I mean tiny). Knock it off with a sharp rap of a hammer against another piece of wood in full contact with one side.

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Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

Sometimes, there are just easier/faster ways to do things than using the cnc...

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"I want to know what kind of pickups Vince Gill uses in his Tele, because if I had those, as good of a player as I am, I'm sure I could make it sound like that.
Only badly."

Indeed Don, but right now my process isn't necessarily easy or fast. I do have a jig to put the radius on a brace, but I don't have a set of profile templates, so I have been drawing profiles on stock and cutting with my scrollsaw. I was thinking of cutting out a set of templates on the CNC when I thought why not just cut out the actual braces on the machine. I still do a fair amount of carving and shaping by hand once the braces are on the soundboard, but I'd like to have more of a consistent starting point.

Ken

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http://www.casperguitar.com

Hey Ken - this is the other technique that I mentioned in that message the other day. Tall/thin parts can be tough to hold...this onion skin method is one way around it. The other way is to machine a whole chuck of spruce all at once and then resaw it (this is what i do...errr...used to do back when I had time!).

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http://www.PeakeGuitars.com

I've had good luck holding wood parts down to aluminum or even MDF when machining. Two or three drops of medium CA on one face of the joint and accelerator on the other. I've found that NOT using accelerator creates a stronger joint that tends to cause difficulty when removing the machined part. Setting the final depth so that it leaves a tool path in the fixture makes for easier alignment of the next part going on to the fixture.
I've also found that roughing the aluminum fixture with coarse sandpaper gives a sufficient bond where smooth or polished aluminum may not. Any CA left on the fixture can be removed quickly with a scraper or whatever to make ready for the next part. Several parts can be fixtured side by side using this method.
Nelson

That's a really good idea. Shouldn't be too much trouble to do 2" thick at a time. Ken hosted a SE Michigan luthier gathering at his house a few weeks back and I suggested leaving the stock long and clamping it at the ends and to only machine the "top" and "bottom" of the braces. Cut the extra stuff off the ends with a band saw.

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