Sam, since you have ran so many of these hammers wich would you reccomend for bladesmithing and damascus making, the 75lb, or 50 lb, or heavier?
I'll give you my $.02 here (even though you asked Sam
)
As with anything, you need to look at the work you intend to do in order to decide what the right tool is. I've run John's hammers in 50, 75, 100, 110, 150, and a one off 20:1 ratio 160# monster. I've forged damascus on all except the 150 and 160lb hammer (though I was breaking down a 4" diameter roller bearing on the 160). If you're going with a starting billet of 1 1/2"x6"x3" or so, any or them will do just fine. Once you get much bigger than that, you will likely see enough of an increase in forging efficiency to look bigger than the 50# hammer. The other reason is that the 50# has smaller dies (4" wide) than the rest of the hammers and as such you can't work stock as large as on the larger hammers. If you follow the rule of "figure out what you need, then go one bigger" like I do, the 75# is the starting point
Between the 75# and 100# hammers there is little difference in construction. They both use identical pneumatic parts, it's just that the anvil and tup weights are different between the two. Effectively what this means is that the 75# will feel more "snappy" in forging than the 100# since it's got the same guts. This same relationship exists between the 125# and 150# hammers. Also, due to the upgrade in pneumatics over the 50# hammer, the 75# definitely hits more than 50% harder than the 50# model.
All of this is rather amorphous when we're just talking about weights and percentages though. Let me give you some real-world examples based on my experiences using John's hammers in demonstrations.
My standard demonstration billet is 13 layers of 1/4"x1 1/2" 1084 and .058"x1 1/2" 15n20 6" long. This makes a billet that is 1 1/2"x6"x2.1". It's smaller than what I work at home, but usually when I'm demonstrating I have 45 to 60 minutes and I like to get through all the basics including cutting and folding a billet. In a 60 minute demonstration, I can go from a cold billet to a 26 layer billet (1 fold) and have it ready to cut and fold a second time with ease, while talking and explaining what I'm doing. It generally takes about 3-4 heats after the welding pass to have the billet drawn to twice it's length and be ready to cut, fold, and weld again on the 75# hammer. On the 50# it's more like 5-6 heats. However, as the billet size increases to 3" tall or over, this gap becomes more pronounced. On a 100# hammer I can do a little better than the 75# with a small demonstration billet, but because of the care required in any forging to keep things straight and square, the gain on smaller pieces isn't too pronounced.
If it were my money, I'd go for a 75# hammer (and intend to, but the shop needs better electrical than an extension cord across the driveway first...). If you plan to work stainless, or really large billets (3"x3"xsomething, etc) you may need a larger hammer, though really at that point you'd be well served to look at a combination of a press and a hammer to maximize forging efficiency.
Here's a couple of videos of the 50# hammer I took at this year's Fire & Brimstone hammer-in. Remember, it was raining all weekend, we were standing in 3-4" of mud, and the hammer was sitting on mud, covered by a 3/4" steel plate, covered by a piece of 1/2" plywood. Not really an ideal foundation.
John Forging a Railroad Spike
Sam Forging 1" W-1 Round
-d
Regards Butch