Machining titanium and stainless steel jewelry

Step 6 Tap the bar

Using a tap, cut threads inside the bar. This is where the balls will screw on. Tapping small holes like this can be difficult- it doesn't take a lot of force to break the tap. If the tap is not perfectly lined up with the hole it will jam and break. I use the chuck in the tailstock to loosely hold the end of the tap while I turn the tap wrench by hand. Use lots of cutting lube, go slowly, and back the tap out more often than you think is necessary. I get into a rhythm of 1/2 turn forward, 1/4 turn back and then completely removing the tap every few turns. If you break the tap, you get to buy a new one and throw away the piece.

One fun trick though, in case you're working on a piece you don't want to throw away. The bar here is titanium and the tap is steel. This means that if the tap broke, you could put the whole mess in a bath of nitric acid, which would dissolve the broken tap piece but not the titanium part. Of course, when you were done you'd still have to deal with whatever problem made the tap break...