I used to make them for sale and donations for various hunting organizations a few years back. Things I discovered while building them were.
1. Cut off antlers polished up and were better for engraving/carving then the shed antlers because they were not as porous. Mature whitetail and mule deer antlers work best for most recurves and smaller ones (3-4 points) for longbows.
2. As mentioned by Mike, JB weld worked great for embedding the nut. I have since used MT-13 for takedown handles and feel it might work better.
3. When embedding the nut, use a high quality nut. I got mine from Hilti, the world’s largest manufacture of nuts and bolts: there quality is second to none.
4. The procedure I used to embed the nut was as follows:
a. Test fit the nut for depth (make the hole deeper then needed for extra epoxy), angle, and the base of the burr to the limb for a "flat fit".
b. Wax all of the parts below, except the nut to be epoxied, to prevent adhesion.
c. Screw a nut (same size) on to a bolt, leaving enough threads exposed to allow for a fender washer, wax paper, and another nut.
d. Add the fender washer.
e. Add the wax paper wax paper to keep the epoxy from sticking to the fender washer.
f. Screw the second “non-waxed” nut (the one that will be epoxied into the antler burr) on to the bolt and finger tighten. Make sure the end of the bolt is even or a little past the end of the nut. The end of the bolt must be waxed or it will not come out when the epoxy sets.
g. Add some epoxy to the hole, but not to much, you do not want to have excess running out when the nut is inserted.
h. This step next is important for proper alignment!! Insert the nut into the hole and use a couple of small spring clamps to hold the washer tight against the antler burr until the epoxy is cured. Make sure the wax paper/washer is flush with the base of the burr.
5. Always use a plastic washer between the antler burr and bow limb to prevent damaging the limb.
6. Next Assemble the limb, with the plastic washer, and antler burr using the proper length all thread bolt and check for alignment, I used feeler gauges. The antler burrs will look better in some positions then others and if you decide to do any engraving they should be set in a vertical format.
7. Check that the antler burr is aligned in the direction you like best. This requires removing the burr and adjusting the all thread as needed. The all thread I used had an Allen wrench hole in the end to allow minute adjustments. It will usually take several attempts to get this correct. At times I had to put a drop of super glue on the nut and all thread to temporarily hold them in place.
8. Once the burr is properly aligned (when the bolt is tightened, but not over tightened), remove the assembly, mark, remove the all thread, and then epoxy it into place using the marks for a guide.
There are other methods but this is the method I developed through trial and error, hopefully it will make it easier for anybody who attempts this endeavor.