Too small keys for hammer dies and sow block

[Steven Bronstein]

I have a 50# Fairbanks and I am dealing with a recurring problem that has plagued me over the years. 

First, the space for the key is 1/4"-5/16". This small a key is prone to bending and mushrooming so removal later can be quite a challenge. I have other hammers where the dovetails are narrower and allow for keys that are 3/8" - 1/2" which is then much easier to deal with. I have never been brave enough to have the dovetails machined smaller to allow for a larger key. Has anyone done this? And would it be a mistake?

The second challenge is the sow block allows for the key to be removed because the dovetail plane is perpendicular to the plane of the machine. The hammer dies sit on top of the sow block and you can only access the key when installing the die. To remove , you have to first remove the sow block to access the key for the hammer die removal. I have reason to change hammer dies somewhat regularly and wish there was a better solution. I know I could replace the existing sow block with a  dovetailed plate and bolt holes so I could use bolt on hammer dies. I have had trouble with this solution because the bolts do not seem to last very long. I hope someone out there has a better way of dealing with this. Thanks.

[aplater]

Hey Steven, we met years ago when I bought a 50 lb LG out of your shop.  I wouldn't hesitate to modify your dovetails to allow bigger keys.  I run 3 hammers in my shop, 50, 100 and a 250 and have made all of my own dies.  I just make them so they work for me and for what I am doing, I  would even machine my sow block if it meant an easier system,  its only metal and if it doesn't work you can always change it.  If you fit the keys well enough the dovetail system can be as quick and more secure than a bolted die system, the guys who designed these hammers came up with dovetailed keys for a reason!  Take care...

[Steven Bronstein]

I remember, especially how we had the hammer lifted horizontally in the air so you could drive your truck underneath. Glad it worked out. Thanks for the feedback. I will cut the dovetails so I can use a bigger key, that makes it so much easier. Hope the die steel isn't too hard for machining. Thanks

[jason0012]

On old hammers with dovetails perpendicular to the frame, later solutions to the key issues were to cut straight dovetails and use a key either side of the die, with opposing tapers. One key locks the die, the other releases it. I dont think this was used on fairbanks hammers, but I don't see why it could not be made to work. This is used in bradley hammers. The long key in this photo is skinney end out and will release the die. The opposite key is fat end out and driven in until the die is tight. Oh and yes I should trim this key...

[Steven Bronstein]

Thank you this is really helpful. There are two keys on my sow block. I , at first, thought that one was just a spacer but now see that it is tapered. It appears both of your keys are reasonably stout.  I still have the original problem which is that both keys are 1/4" at the thinnest end and start to bend as soon as I try to remove them. This is why I was hoping that  ( when I finally manage to get them out) I could reduce the size of the dovetail and increase the thickness of the keys. Any suggestions?

[Irondragon Forge ClayWorks]

That's what I did with my Star. Used an angle grinder to reduce the dovetail and forged thicker keys. I don't think the dies that came with it were original.

[jason0012]

I have that issue with my top die. I need to thin the dovetail, but have managed for more than 20 years with skinny keys. Use spring steel, heat treat the keys and use a close fitting drift to push them. Keep them reasonably close the length of your dies. Soft keys are evil and the cause of every die I have ever oxygen laced out of a sow block. At this point in my life I dont expect to live long enough to waste my time trying to dig a riveted die out of a hammer ever again.

Here is a better veiw. My top die keys are about 3/16" at the thick end. The right key is the thick end. The thin end is a tad under 1/8". These keys were fitted to this hammer in the 90s.

[Steven Bronstein]

I have the same setup. It is funny how the bottom keys are so large and the top so small. I was always concerned about using tool steel thinking I wanted them to move in case the dovetails weren't straight. Didn't want to crack the sow block. I am guessing that since you fitted the key properly it wasn't an issue because you wouldn't have to overdrive them. I will give it a try before messing with the dovetails. Thanks.

[Greebe]

You could just mill the die block if they are not crazy hard. Do you know what the dies are made from? The other option would be to make a new top die with smaller dovetail. Then you could save the original without worry of wrecking them. What are the dimensions? I have a machine shop and could do the work for you if that is something you were interested in.

[jason0012]

On 4/14/2021 at 9:28 AM, Steven Bronstein said:

I have the same setup. It is funny how the bottom keys are so large and the top so small. I was always concerned about using tool steel thinking I wanted them to move in case the dovetails weren't straight. Didn't want to crack the sow block. I am guessing that since you fitted the key properly it wasn't an issue because you wouldn't have to overdrive them. I will give it a try before messing with the dovetails. Thanks.

Even a soft key can crack the dovetail. You will gain a smidge of crush value with a soft key, but it is pretty minimal. Any deformation of the key in the slot tends to lock it in place immovably. I have seen wavy keys used in hammers that would not behave, they are impossible to remove without destroying the key and/ or the die. A really good solution in my case would be to mill 3/8" off the dovetail and make thicker keys, and some day I might. I made these dies just guessing what size the dovetails should be. After finding a factory set I see how wrong I got the top dovetail. Factory is almost a half inch narrower