I picked up a circular saw this weekend and constructed a rail assembly. It is made from a couple of drawer rails attached to the saw by the saw's rip guide and a little extra steel. The rails will be mounted on the frame of the gear tooth cutter so that the saw travels vertically. The cutting angle of the saw can be adjusted to accommodate different gear pressure angles, although I plan to only use 20°. We'll have to cut one side of the teeth with one angle and the other side with another angle. I had hoped to use the saw's angle adjustment to accomplish this, but I couldn't figure out a good way to mount the rails for dual-angle cutting without the rails getting in the way of either the gear blank or the saw's motor. We'll have to flip the gear blank over instead.
I tried my hand at ice welding for the first time tonight. I used an iron to melt two flat surfaces and let them freeze together. The resulting bond was pretty strong; I couldn't break apart the two pieces by hand without using another object for leverage. The ambient temperature was around 15°F. This is something we'll need to practice quite a bit as the strength of the bond is clearly dependent on how well the pieces fit together. We may want to use some kind of hot plate with perpendicular guides.