The material varies by manufacture, but I do know that Catapillar still uses 4140 or 4142 for their pins. I've used a lot of it for toolig.....I really like it for making spring fullers for the air hammer. I use 1 1/2" square stock in 4140 for building all the forging hammers I make..... the biggest thing I've found with it is you have to be careful when hardening/quenching it in larger cross sections.....get it a bit over it's critical temp, and/or cool it too quickly and it will split on you. It took me a while to figure out the right quench for larger sections of it.....but eventually I discovered 2/3 SAE 30 motor oil and 1/3 hyrualic fluid makes a good quench for hammer sized pieces. (it also takes a LOT of quenchant... I have a 20 gallon steel drun that holds my hammer quenchant.)

I once made the mistake of trying to quench one of my forging hammers in Parks 50.....it came out looking like a window that had been hit with a baseball! <img src=' http://www.americanbladesmith.com/ipboard/public/style_emoticons//blink.gi f' class='bbc_emoticon' alt=':blink:' />

Ed, Johnny Jones of the "Little Johnny Forge" told me the same thing. It spark tested in a way that made me think that too. Thanks.

Incidentally, something you might consider when quenching a hammer head: I have read about, tried, and had success quenching by differentially hardening them. I set up a bucket to sink the cross peen (maybe an inch) in while running a smooth stream of water (by water hose) directly over and square into the center of the hammer face. This leaves the eye and middle of the head more or less out of the quench since the water will steam off as it trails over the edge of the face. It also hardens the face in a targeted (bulls eye) shape where the middle of the face gets hardest and the edges and corners slightly softer to prevent chipping these susceptible areas. You will have to use a hose to get the control and accuracy. By targeting the quench in this way you can get away with using water. Just thermo cycle as you would any steel you would want to be very tough before the quench. This is the method some of the old timers used.

well that's pretty neat guys! I found a bunch of these over the years while hunting my old hog land in SC so I assume the guys doing the logging lost them while performing thinning operations....they've got a big hole going through them on one end, right?