How to Turn a Wood Cap Nut?
I bought a used machinist vise at a great price. I needed one for a long time. The only issue with it is that one end cap nut on the handle is missing. I figured that I could turn a replacement cap nut easily enough, right?
Here are the specs:
* The metal rod is exactly 5/8 inch in diameter.
* I used a ruler, and counted ~2 threads per 1/8 inch. That makes 16 TPI. My guess is that the cap nut is 5/8-18 which seems to be a common size.
-> Do metal thread specifications use the outer (uncut) diameter of the rod?
After 10 tries, it isn't working out. My problem is limited tooling. I don't have a matching thread tap. I have Forstner bits, 1/16 inch apart. Here is what I tried that didn't work:
WHAT DIDN'T WORK:
* Drilled a shallow 5/8 inch hole as a guide to keep the rod straight.
* Drilled a deeper 9/16 inch hole inside it for the rod.
* Did a rough rounding of the outside on the scroll saw and bandsaw, whichever was handy for the next try.
* Used the rod threads as a tap for screwing the rod into the wood. It was VERY tight; too tight, really. Despite the 5/8 inch guide hole, the rod didn't always go on straight.
* Inserted the rod in a four-jaw chuck on the lathe and stabilized the wood piece with a live center. It looks straight and good. The rod end has no visible runout when I turn on the lathe, live center or not.
* Using sharp tools and the lightest cuts I could master, I tried to turn the cap.
* I tried it on softwood, "medium wood" (poplar), and hardwood (maple). I drilled the holes in side grain, not end grain. The turning was like a bowl blank, not an end grain "cookie".
-> There were various failure modes, but the cap consistently failed with large pieces cracking off. My hunch is that there is too much internal stress from screwing the rod into the way-too-tight 9/16 inch hole.
I could buy the correct tap. I could buy a nut or pay a lot for a cap nut (the ones I found are chrome plated for Harleys). I prefer to make something myself, using materials on hand, and I am enjoying the challenge. I want the cap to be removable, so I can replace it in case something cracks or breaks later.
I thought about wrapping the end of the rod in teflon tape, drilling the larger hole, and using hot melt glue or epoxy. The teflon tape would keep the glue from bonding to the rod, so I could unscrew it later.
-> Would teflon tape prevent hot melt glue or epoxy from adhering to the rod so I can remove it later?
-> What would you do? How would you make this replacement cap nut?