I wanted an oversized bolt knob for my SPS tactical and found one that I liked on Ebay for 20 shipped. Nothing fancy... just oversized, so I bought it and it came in yesterday. I had planned on sending my bolt out to get threaded but got the itch yesterday to try it myself. I brought the bolt out to my garage and unfortunately... fogot to bring my camera, so I'm sorry to say I don't have any progress pics, but it went so fast I didn't think to go get it.
First I taped it all off, then ground the existing bolt head to a .310 square shape. I used a 4" angle grinder with a 40 Grit flap disc.
Then I switched to a worn 60 grit disc, and rounded the square. it was by all means... not perfect. It looked like a square with rounded corners.
Then I stuck it in a vise in between some wood, and threaded it using a 5/16"X24 die.
I did slip a little with the grinder at one point, and you can see it after the bolt handle is threaded on, so I used a cold blue pen on that mark. It's barely noticeable now.
All in all, I think it turned out great, I should have taken a pic before I Loc Tited it on the threads, they look perfectly round now. It's very solid, and much more easy to manipulate with the larger knob.
The entire process from start to finish took less than an hour, and that's with my walking next door to borrow my brother's T handle since mine was missing. I wont send out my next one either.
Here's some after pics, sorry I didn't get some "during".
bolt handle 001.jpgbolt handle 003.jpgbolt handle 002.jpg