I think I've found the ultimate hold-down solution!

I'm running a 36 x 36 CNCN router, mostly making inlays for custom woodwork. I've struggled with hold-down issues since the beginning. I cut 1/8" wood for the inlays and have been breaking about 70% of the inlys when trying to remove them from the spoil board. Vacuum hold-downs don't work because I have to cut all the way through the inlay stock. After many, many iterations, I've stumbled onto the best solution. I use a well-polished phenolic spoil board and use 3M9576 double-sided tape to hold 3/32 balsa to it. Then I use the tape again to stick the inlay material to the balsa. The balsa is easy to cut through, either with a VERY sharp putty knife or a fine-bladed bandsaw. The tiny inlays come off without a problem. The 9576 tape is teh best approach I have found for this method. The adhesive rolls off easily, leaves NO residue and holds very well. The bals is much more stable than nay type of styrofoam board I've thried and relatively inexpensive. I put the balsa down in 1/2" wide strips with the grain going across the tape. Most of the tape and its adhesive comes up easily and the rest rolls right off under thumb pressure. My biggest problem is getting a blister rubbing the adhesive off!

Save your thumbs!

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I don't understand the purpose of the balsa. To describe things as I understand them, you have two layers of double-sided tape and a layer of balsa between your inlay and the phenolic spoil board.

Then do you cut all the way into the spoil board, or just into the bottom layer of tape? What are you cutting with the knife or bandsaw?

I'm cutting hardwoods 1/8" thick into inlays of names, dates, etc. The balsa gives me somewhere to start the "unsticking' of the inlay from the hold-down (I shouldn't have used the term "spoil board") board. If I stick the inlay material down to the hold-down board, I can't get the inlay off without cracking it. The balsa gives me something relatively soft to cut through to get the inlay off the hold-down board without cracking it. Then I peel the tape and balsa left-overs off the back of the inlay. Using the 9576 tape, the adhesive holds like mad but rolls off without too much trouble. I cut the balsa into 1/2" wide strips so it's easier to get through with the sharpened putty knife. The balsa provides a "gap" between the inlay and the hold-down board and is easily cut through. It's also WWWAAAYYY firmer than foam board and doesn't allow the inlay material to budge while it's being cut. I cut all the way through the inlay material and the first layer of tape, into the balsa, without going into the second layer of tape or the spoil (hold-down) board.

Thanks for the explanation. Have you ever used this tape to hold down thicker parts that you want to cut all around? I thinking of 1/4" plywood or something similar.

Have you ever tried drawing a thin wire (like a guitar string) through the tape to cut the work piece away from the backer board? I'm not sure how much force that would take, plus the tape might just restickto itself after the wire passed through.

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Originally Posted by electronicwood

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Have you ever tried drawing a thin wire (like a guitar string) through the tape to cut the work piece away from the backer board? I'm not sure how much force that would take, plus the tape might just restickto itself after the wire passed through.

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That's very clever! :) I'm imagining something like an archer's bow, with a very fine guitar string under a lot of tension. The bow of course means you can use a fair bit of force and even a "sawing" motion.

A plant I used to work at we applied mirror to doors with foam..
if the mirror cracked we had to remove and replace it..
we had a thin wire of some sort with a dowel at each end..
wire was wrapped around the dowel and then twisted around itself..

I recall once the wire broke on the wrap and sliced my finger pretty good so be careful if you try this..

You can also use dental floss, just go back and forth in a sawing motion. I used this many times taking the badges off of cars with good results.