I get the weird jobs nobody in this area wants to mess with. I swear ten guys will come into my shop and they don't have a full set of teeth between them. Anyway I have to cut two pto shafts and join them together. The reason being that one of the splines in no longer available. Anyway I've been looking into ways of joining two shafts which include a keyed coupling, a welded coupling and a cross pinned coupling. I want to go with something that if it does fail, I can go to plan B without destroying the shafts. I am leaning towards cross pinning with 1/2" pins (shafts are about 1.5" D. If the pins shear I just move on to something else. My question is what type of steel should I use for the pins? I don't want anything real brittle but plenty tough. I have some 4140 but I'm just not sure. I also have O-1 and various tons of mystery metal.