Got your interest with the title, but first, let me gloat over my two new hammer heads; Left I will use to set saw teeth, the right I am thinking of trying to make a saw tensioning hammer out of.
I was worried about making one, being unable to forge...until I realized, oh ya, metal isn't hard to bend, especially Home Cheap-O mild steel in a vise with physics working for you.
After bending, I filed rough points onto the ends, drilled two slightly-smaller holes, and banged on the thing until it was about halfway through the wood. I then cut some wedges, don't know what angle; and went to see if this thing worked.
This is the first time something has worked on the first try. This staple vise is so much better than a holdfast.
Here are my 'sen'...The right is an old laminated blade I tried making into a kanna blade, complete with mock-hollow. It hurts to use, I can't figure out a way to make a handle for it. The chisel works better.
Jason said that sen should be rounded slightly, sharpened at a very coarse grit, and used at an angle to the surface. Like, your going straight, but the blade is angled, sort of like using a plane on challenging wood.
Pretty nice! This sen-surface is lovely. This is my attempt at an azebiki nokogiri, New York style, with my attempt at 'progressive' teeth and a dual-sided flush cut saw. I have the rip teeth done so far on the azebiki nokogiri. For reference, the chisel is a 1/2" chisel.
Better shots of the teeth of the flush cut, one side crosscut one side fine rip.
The cut surfaces are pretty smooth, I need to make a handle for it, though. Cuts pretty fast, for my first saw.
It took quite a while to make, but it should be useful. I learned a tremendous amount making this saw; I experimented with many different ways of creating teeth, you can probably tell.
I ended up making the crosscut teeth by holding the file slightly upwards, at around a 15 degree angle, file one way, flip the vise around, file at the same angles, and you get a nice crosscut tooth. Repeat this, and I got nice spacing, similarly-shaped teeth. Finish up with the third facet, and there you go!
The teeth came out chubby, which is OK, after all I will use it a lot for plane-making.
Gather around, children, for spooky tales of woodworking horrors...
These teeth are on a very large ryoba I have. It has a loud voice, likes to be heard, and isn't shy to sing you a ballad; it sounds real nice, so it's fortunate for me. Nice signature, it had quite a bit of rust on it though.
Odd, though: The nicks in the teeth. I guess even masters have that problem. Or maybe it was intentional?
I am a cynic, in that I often see things as mistakes instead of 'on purpose'; after all, woodworkers are often guilty of 'inspirational design changes' when a project goes wrong. A song played wrong is an 'interpretation'.
I just can't see how this nick would help in the sawing. And when it happens on each tooth...Well. My prevailing theory is that the sharpener or forger, or possibly user, was tuning the teeth and the file needed also coincidentally filed slightly into the next tooth. Doesn't effect sawing, so it is left there.