I just hate to throw away perfectly good diamond sanding belts when the abrasive is worn out. The belt integrity seems fine but the diamond abrasive is gone. With diamond powder so unbelievably inexpensive on eBay, I thought that with a little ingenuity, I could make a good working belt out of an old worn out belt. And I did! I believe this procedure will work for soft diamond sanding wheels as well.
Enough bragging…let’s get down to it…I clean the belt or wheel thoroughly with acetone. Read the warnings on the acetone can…its dangerous stuff. For a good epoxy bond the belt must be immaculately clean! Place the belt over an expanding drum or old grinding wheel of the same diameter (just to give it a solid backing) and suspend on a dowel between two stacks of books or boxes so the belt/wheel hangs free and can be rotated easily by hand. Most recently I have been refurbishing the belts, on my cabbing unit, by removing the top for better access (if your unit has that capability). It’s MUCH easier.
I use Hughes Epoxy 220 made by Hughes Associates out of Wayzata MN. The epoxy hardens without becoming brittle and mixes well with the diamond powder. I use the small plastic measuring cups for liquid medication doses that are available in drug stores, for measuring and mixing the diamond/epoxy compound. Mix 1teaspoonful equal amounts of hardener and resin in the small cup. Then very slowly pour in a 5 carat vial of the appropriate grade of diamond powder and mix very thoroughly again. Pour in a VERY small amount and mix; repeating this procedure several times until the whole 5 carats is finally in the resin compound. This is not “5 Minute Epoxy” so you have plenty of time to mix. Mixing is very important here as small lumps of abrasive will lower the effective grit of your abrasive and cause the finer abrasive grades to cause coarse scratches. Mix…Mix…Mix…Mix…Mix.
I only use this procedure only for abrasives as fine as 1200 grit. It seems with even the most careful mixing there is still some clumping of diamond powder. And with anything finer than 1200 grit the abrasive mix may be compromised. 1200 grit belts I’ve refurbished cut faster than new factory 1200 grit belts and that may be due to clumping of the grit. I’m just guessing here as I haven’t tried anything finer than 1200, but finer prepolish belts seem to last almost indefinitely so the point may be mute. But some of the cutting speed may be due to a higher concentration of diamond powder, than factory made belts, in refurbished belts.
I’ve spoken with diamond abrasive belt manufactures about diamond/epoxy mixes and they’ve indicated grit clumping is a difficult obstacle to overcome. And, of course, their mixing process is proprietary.
Apply the epoxy/diamond mixture to the belt smoothly using the disposable acid flux brushes pictured below (available at hardware stores). Apply in a thin coat so there are no lumps or thick areas. The epoxy sets up in one hour (hardens in 8 hrs) so constant attention is required with slow rotation to keep mixture from running on the belt. One teaspoon of epoxy mix (and 5 carats diamond) is enough for 1-6” X 1.5” belt or wheel. I usually have a little left over. Ten carats is about right for an 8” X 3” belt. I would toss the used brushes so you don’t cross contaminate although they can be cleaned with acetone and reused for the same grits or coarser.
I recently finished a 600 grit belt and it cuts faster than a new belt just out of the box. I have an older 320 grit diamond-sanding belt that I refurbished a couple years ago, and it seems as though it will never wear out. Bear in mind I am mostly cutting opal which is softer than quartz gems.
Note: Even if a thick coat is applied uniformly, it still tends to run before the epoxy sets up, giving you a bumpy belt (though they are certainly still usable…I have a bumpy belt that has been used for several years and is finally beginning to smooth out as the diamond/epoxy wears off). So I now use 2 thinner coats (1/2 the diamond powder per coat) rather than 1 thick coat, to give your wheel extended life and much smoother cutting. If you have any questions, corrections or tips please give Steve a call at The Village Smithy Opals, Inc. 406-651-4947 (office) or 406-208-2577 (mobile).