I recently saw an article explaining how to modify the ABANA treadle hammer so that one can put top tools in the hammer head, and bottom tools in the anvil . An obvious use for this would be to use top and bottom fullers to really stretch hot iron fast. Unfortunately, as the author of that article discovered, the hammer head swings in an arc so the fullers or other tools don't necessarily line up! His solution was to make serious modifications to the hammer arm support mechanism, adding a rack and pinion affair to raise the whole thing up and down so the tool in the hammer would line up with the tool in the anvil. Top tools are held in the hammer head by a wedge. You adjust the drive rod length each time you adjust the hammer.
All that sounds do-able, but I had three problems with those modifications:
1. I am basically lazy and that sounded like a lot of work, having already built my hammer . It also sounds like a lot of work every time you change tools.
2. I can't give enough credit to Gade and Marx for the elegance of the original design of that hammer and I hate to see complexity of construction or usage added to the basic tool if not absolutely necessary.
3. In order to make this modification work, you have to make a hardy hole in the hammer head, This, in my mind creates two problems for me:
A: I don't WANT to use a top tool very often. But I DO use the hammer to strike small chisels A LOT! So, what do I do with that empty hardy hole up there? If I make a plate with a hardy to cover that hole I am faced with the possibility of those extra parts coming loose, and of course it would add extra weight to the head.
B. I am very concerned about the wedge sticking out anywhere around the hammer when my one and only head is only inches away and my hands are constantly moving around in the area too.
So here's my solution: ----
Look at the drawings (Sketch Link above) of this Removable Hardy Hole. You simply attach it to the hammer head when you need it and take it off when you don't. It adds about 5 pounds to the head. The ONLY modifications you make to the treadle hammer are the two tapped 1/4-20 holes you put in the side of the hammer head to support the removable hardy hole when it is in use. Of course you also need to make a hardy hole in the anvil, unless you make a "Portable" for that end, too. Many of us treadle hammer users had cut a hardy hole in the anvil anyway. I have a plate the same size as the anvil, with a hardy stem welded to it. I use it most of the time. If it ever gets beat up too much, I can just make a new one.
The links above are almost self explanatory. Make the Removable Hardy Hole before drilling the mounting holes in the hammer head. Then position the tool on the hammer head to locate the holes to the best advantage for the tools you might use.
The block that you cut a hardy hole into can be 1 3/4" square or 2" square. The length of this block is to be exactly the same as the width of the hammer head. To cut the hardy hole, choose the size you want, mark it out, centered, and drill 1/8" holes in the four corners of the square. Then drill the "main hole". Hopefully you can drill to the same size as you want the hardy hole to be, (or even 1/64 inch larger.) By drilling those little holes in the corners first, it reduces the amount of material you'll have to file away by a lot!. I drilled and tapped a hole for a 3/8-16 allen set screw to retain the hardy tool. It is a short set screw, so that none of it protrudes. When you mount the tool, make sure that the set screw is to the rear of the hammer.
The side plates are 2" X 2" X 1/2". Drill and file a 1/4" wide slot, 1 1/2" long in each plate and weld them to the "hardy hole block". This 1 1/2" long slot allows all the adjustment you need to handle a combination of hardy tools and work that add up to about a foot in overall height. (I figured that you need at least 6" of clear distance to get the hammer going before it hits something!)
Tap the two holes deep enough so you have at least 6 or 8 threads holding the bolts. Remember that the basic tap has a lead of several threads so you will have to tap 6 or 8 extra threads to make sure. Use grade 5 or grade 8 bolts with a helical lock washer and a flat washer on each one.