I finished the big 2 inch diameter, 2 thread per inch nut for my cider press screw today. I really buggered up the tap I turned from cherry yesterday while trying to cut the mortice for the cutter. So…early this morning I went to my firewood pile and pulled out a likely piece of straight grained oak to turn another. This one went a little faster than the first but chopping a mortice for cutter and wedge in round stock was no picnic.
At first I tried a threaded insert and screw to hold the cutter in place. All looked good, so I tried it out in a piece of pine. It cut the threads beautifully…however, the torque placed on the cutter pushed the insert out, taking a chunk of my tap with it!
I then decided to go the traditional route and hold the 1/2 inch cutter in place with a carefully fitted wedge. When everything looked right I cut (scraped, actually) threads in the piece of locust previously prepared for the nut. I found it worked best if you ran the tap through, backed it out and cleared the chips then ran it through a second time before advancing the cutter. The cutter is advanced by tapping it forward with a screwdriver and mallet. It took about 40 minutes and numerous passed with the tap to achieve the final results. You can see the tapping jig/machine set up for action below.


Here’s a close up showing how the tap is pulled through the workpiece by a piece of sheet metal running in a spiral groove:


I am very pleased with the results. Nice crisp 2 threads per inch in a locust nut.


Now to make the screw…but that’s another day!