Rich,
How did you make that cutter?
Thanks,
Rob
Rob,
Step 1 was drilling a hole a few thousandths larger than the body size of a #5 screw down through a piece of drill rod. It is not perfectly centered but it doesn’t matter in this case unless I was making screws with wide heads.
Step 2 was filing the teeth. It took me 3 tries to figure it out. The cutter has to have teeth that oppose a clockwise drilling action. In my final successful try I made marker cuts like spokes then used a triangular file held with one edge vertical to start the teeth. It’s tricky because the file cuts cannot cross the center and the hole is small. I learned that for the cuts for the teeth to widen out toward the edge of the cutter I needed to file deeper there and swing the file to the side a bit. It was important to get all cuts outlined so one tooth notch leads to the tooth peak to the right. I know, confusing!
After filing the teeth I worried they might be of different height so I chucked the cutter in the drill press teeth down and ran it gently down into a diamond sharpener. That leveled and squared everything then I retouched the teeth.
Step 3 was brazing the cutter to a scrap piece of steel. I’m out of Mapp gas so used propane in a fire brick cubby. Took 5 minutes to get to brazing heat. I pre-flux with a fine mix of borax and water.
Step 4 was drilling the hole down through the base of “handle”.
Step 5 was hardening the tip of the cutter. I put the assembly back in the fire brick cubby and got the top of the cutter to orange and quenched in canola oil. Note that quenching temperature is under what it takes to braze, so the joint was not at risk. Brazed parts can even be pack case hardened because of this.
Step 6 was tempering the cutter to dark straw/purple by eye.
All in all a fun project. And it sizes rough filed screw blanks very uniformly though the surface is rough. My first attempt was using drill rod with the shaft filed square then octagon and tapered slightly. I bet it would cut mild steel even better.
I might make a series of these for #5-10 screws and maybe even 1/4” for top jaw screws.
