I need adapters to put in the end of some 12 inch bolts that I am making for crossbows. I can drill the end hole to place the adapters, http://www.lancasterarchery.com/easton-st-rps-inserts.html

Are they just epoxied in? We are making 12 inch bolts for our homemade crossbows using fiberglass electric fence posts, I can sharpen the points on my lathe, but some want the broadheads. I can make 4 bolts for a $1.69 plus some duck tape for the fletching. I have no problem drilling for the adapters, I already tried that.

Epoxy works fine for holding the inserts in place. They are basically a long 8-32 captive nut. Key is getting the hole straight and in the center along the axis. With your skills I doubt that will be an issue. On the epoxy I have glued bunches of them in with 5 minute epoxy.

Checking if the insert is straight in the bolt give it a spin test and see if there is any wobble.

I thought that was how they work, I will be drilling the hole on my lathe, it will be easy to centered on the bolt's axis. Thanks

Check these out, made for using screw in broadheads and points on wooden arrows.
https://www.3riversarchery.com/wood-screw-point-adapters.html

I saw those, we decided with the 3/8 diameter of the fiberglass we will buy some 5/16" diameter aluminum rod, cut off 1" lengths and drill and tap for 8-32 threads. I may try to just drill and tap the fiberglass rod, it seems heavy enough to take the threading and hold up. These are for toys, less money spent, the more toys we can make.

Cool idea, let's see them when your finished.

On that if you use the Hidden inserts for say axis arrows you will have more fiberglass around the insert than for standard inserts but will need to drill out the hole deeper.

Lancaster hidden inserts link

The brass ones weigh 75 grains r 50 if you break part off

We have pretty well decided to drill and tap the fiberglass to start. My cohort in this project tried one last night, he drilled and tapped the fiberglass. He shot at a 1/4" piece of plywood with a field point, it went through the plywood, and stripped the duct tape fins off of the bolt. For a toy, he declared it good enough.