Does anyone do this? The method I am using is a 3/8" threaded bolt screwed into the rolling nut, as per Kurt's (Knight's Armoury) build along. He, as far as I can tell, does not heat treat these parts.
One option is to heat treat / temper using a Mapp torch, which I have in my shop. Another is to use Grade 8 vs. Grade 5 bolts, which are fairly easy to find. Another is to find a hardened threaded bolt, whiich is not easy to find, I think. My local auto parts store doesnt carry them, so I'd have to find a vendor online, probably.
Besides the sear, the tickler where it engages the sear may need heat treating as well.
Or, am I worried for no reason? The crossbow will be about 175 lb. draw.