A while back my friend Nick asked me if I would make him a specialized leatherworking hammer: a square headed hammer to flatten the stitching on knife sheaths. He gave me some rough dimensions and weight of what he had in mind.
The head should be between 70 and 80mm, one end a square measuring 25mm x 25mm and the other end rounded. He also asked for a weight of between 160g and 170g. Based on these parameters I made a simple drawing of what it might look like.
I used a 35mm round bar of Arne® steel (a manganese-chromium-tungsten alloy, similar to 01 tool steel).
When I had finished the lathe work the hammer head came to 192g which made me confident that the finished product would be in the 160g+ range.
The next two jobs to do where on the milling machine where I had to mill the eye of the hammer and the square edges of the head. This is where I made a rookie error. I milled out the eye then clamped it in my collet block to start cutting the square. I had forgotten to mill a flat reference to make sure the eye and square head would be perpendicular. Sure enough they weren’t!
It was careless, but thankfully not a total loss as I re-machined the square into a round head and made Nick a small ball-peen hammer (145g in weight).
Nick made his own handle.
Learning from my mistake I started again. I used the same type of steel only bigger in diameter (40mm) and made some changes to the overall dimensions of the hammer.
Making the half round grooves I used a grooving tool and a round file.
The arc head shaped with a file and finished with 2000G sandpaper.
The thickness of the bigger head reduced from 11mm to 7mm, was finished with 600G sandpaper.
Careful enough this time I didn't forgot to mill the flat on the hammer's head for reference. The flat surface aligned with the DTI on the square collet block and the rest was easy.
For the handle I used Padauk
The hammer was hardened to 54Rc; the faces got a mirror finish using 3000G sandpaper and a good polish on the buffing wheel.
The overall dimensions of the hammer are:
Body and front head diameter 20mm
Square head 32.5x32.5mm, 7mm thick
Hammer eye 18x8mm
Total weight 169gr
Handle total length 170mm
Regards from sunny Greece