So I’ve been working on a new CNC mill and I’m using ACME rods to drive the x and y axis. An ACME rod has fewer turns per inch and allows the machine to move twice as fast. The only downsides are ACME couplers and nuts are expensive and difficult to make without $40 ACME taps. I stumbled onto Michael McKinley’s site and decided to try making a homemade tap. He used a drill press and a file for his. I wanted to spice it up and used a Dremel and belt sander, it took 30 minutes and saved me a lot of money. Best part this trick can be used on any threaded rod as long as the material you are cutting into is soft. Michael’s site has a lot more detail on the angles of the flutes and how to cut the reliefs. I winged it since I was only cutting delrin plastic. I might fine tune it at a later date if I want to try some soft aluminum.
I colored the flute of the tap to show it more clearly
This was the first thing I tested the tap on, just some scrap Delrin plastic.