Building A Boring Head — Part 5

Previously, I discovered that I had made the internal thread in my boring head too large. There was no way it was going to fit accurately on a standard 3/4 – 16 thread. And then some members on the HMEM forum pointed out what I had been overlooking: I have a lathe. If I screw up and make an over-sized nut, I can just make an over-sized bolt to match. So that’s exactly what I went about doing to make an arbor.

I started by turning a 0.5″ diameter shank 1.5″ long from some 12L14 mild steel. I also turned down a small section right next to the jaws so I would have a reference surface that is concentric to the shank.

I then turned it around and used the reference I made before to center the part in the 4-jaw chuck. Since the whole boring head will spin around this part, it is important to make this as concentric as possible. Any runout here will transfer down the line later.

The end was turned down to 0.765″ diameter, and a relief turned.

And then I cut 16 TPI threads into it. I kept taking off small amounts until it just threaded into the boring head.

It threads in nicely. No binding, and no play. That’s one less scrap part, so It’s time to move on.

Previously, I discovered that I had made the internal thread in my boring head too large. There was no way it was going to fit accurately on a standard 3/4...