Hi Andrew,

Why do you want to make one? Unless you just want the experience of course. They're not very costly to buy.

It is possible to cut a tapered thread with a taper attachment on a lathe.

It would be possible to set a bar at the back of the lathe at the correct half angle for the taper, disconnect the cross slide and use a strong spring to pull a roller or follower attached to the cross slide against the bar. Put on the cut with the compound slide.

Even better than the spring, mount the tool at the back of the stock and the cutting force will always push the follower into contact with the fixed bar.

Offset the tailstock (perhaps by means of a boring head mounted in the taper and a centre in the place where the boring tool would go) so the face of the cone is parallel to the lathe's travel. You might need ball centres or a bell centre drill at both ends as the taper angle would be relatively big, and you would need a driving arrangement at the chuck end that ensures uniform angular velocity (I think it is called a compensating drive dog). That would give you a very skewed thread, but in this application, it would not matter.

I believe there were some lathes made where the power cross feed could be engaged at the same time as the longitudinal feed.

I used a taper turning attachment when making my ‘tail’, but I recall there is a guy on YouTube who made some freehand.

Tony

Use a hydraulic copy unit with a simple tapered pattern:

In this instance set up for cutting 3/8" BSPT threads:

Andrew

Hi Andrew,

Something else occurred to me. I'm not sure, but polishing mops may, to start with, have a parallel bore. A simple mandrel may work for you. A coarse thread may help, but check the direction of rotation.

I'd check the mops I have, but they've all been on pig tails so have tapered bores.

Good luck with the "challenge" if that's the route you take.

The beauty of pigtails is that the mops are self tightening up to a point and don’t require any tools for quick fitting and removal. The mops can also be made with a wide tolerance on the size of the bore and still work. It’s a concept that has stood the test of time.

Turn the taper. Disconnect the cross slide lead screw so you can push the tool into the job by hand. Set up for screw cutting and make a number of passes from the headstock towards the tailstock. This works for cutting the grooves on Fusees for clocks. You are only mating with a mop after all.

regards Martin

Even better use a Coventry diehead that opens up as it moves forward thus cutting a tapered thread:

Andrew

This is just what hand chasers can be used for to great effect. Put a piece of square bar in the toolpost at the angle you want and then cut your thread by allowing the chaser to cut the thread, sliding along the bar.