How to grind a portion of the threads off a hex bolt

metal

I need to grind down the threads on a 4" hex head bolt while preserving 1 inch of threads closest to the head. I need to do 5 bolts this way. I'm thinking bolt in vise and then using a belt sander. Have any other suggestions? I am using the modified bolts to create a roller bar on a trailer. The nut will be welded to a bracket, the bolt will be inserted then threaded down to lock in place. The roller bar is water pipe with a roller bearing insert, that's where the smooth part of the bolt comes into action.

Best Answer

If it's not important for the shank of the bolt to remain perfectly round then a belt sander with a coarse grit will do fine. The 80 grit is the most fine I'd try; 60 would be better. Grits as coarse as 36 or even 24 are routinely used for fast material removal by an angle grinder when working with steel. You could get a belt that coarse but it will leave a rougher surface compared to 60 or 40.

Assuming that your bolt is fairly small in diameter it might be slightly easier if you can fix the sander in place and manipulate the bolt instead. Ask an assistant to hold the sander upside-down on a work bench. Then hold the bolt to the belt while rotating the bolt. You'll be able to see the work as it progresses and it'll be easier to control. The bolt will get hot quickly; plan on using pliers (locking pliers if possible) to hold it.