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When I made my MDF sanding dish I used cloth-backed abrasive strips 4"1/2 wide and stuck them down with double-sided tape. When I tried to get a piece off the other day, it took a layer of MDF with it. I'll probably have to make another dish. Is there an adhesive which will hold the abrasive firmly enough, but let you peel it off if you need to?

You might try a few coats of oil based varnish first. That holds the surface together. I haven't tried a coating of epoxy, but that might be even better. Double sided tape comes in different strengths, and you would want to test some and get the weakest. I have also used rubber cement. You apply that to both surfaces and let totally dry before attaching. It grabs well, but also releases better than stronger contact adhesives.

I use polyurathane but it matters not Like Todd advised schellac , that works well also, get a good coat of some finish. I also use a PSA adhesive backed paper. I have yet to have to change a paper. I also use the hair dryer to heat the glue to release . I did pull one off and had the same result. That is why I seal them up.
john

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

Don't scrap that dish! Fill and fair with Bondo - I seal both sides of my dishes with 2-3 coats of epoxy, sanded out as smooth as possible, and then wax with Butcher's or similar, wiping off as much as I can. Coating with shellac or varnish will work, but won't protect from humidity like epoxy. Spray 77 or even 90 is the ticket, heat gun to release.

Dan

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Dan
http://www.acme-archtops.com

Shellac is an effective sealer against humidity.

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Thanks everyone for the advice. I suppose if I pull off all the abrasive strips I can then do as Dan suggests and re-surface the dish with 'Bondo'. I imagine that's the 2-part paste filler you get from auto shops? I've just spent an hour searching on the web and 3M 77 doesn't seem to be available over here (France). I can get 3M Photo Mount, Spray Mount and Re-Mount, I don't know whether any of these would do. Is the self-adhesive sandpaper that Stewmac sells tough enough for the job and would it be easier to get off if I needed to change it?

Bondo or similar body shop filler works. Practice on some scrap. After the intial set (about 10 minutes or so) the material is the consistency of like cheese and gradually hardens. It is easier to work before it gets really hard. If you wait until totally hard and if you over filled, you may have much difficulty sanding it back. You will be much better off if you try not to apply to much surplus.