Thread: ID these parts please?

One has a 35T gear and the other a 38T gear. There's an oil nipple and an oil groove running down the shaft.
They look like thread chasing dials from a lathe, but I can't work out why they have the same number on every index. A search of google images for thread chasing dials provides hundreds of images, but none of them have the same number at every mark on the dial.

Gawd, I've posted this in the wrong sub. Can the mods move it please? Sorry

Thanks mods. Anyone want to have a guess?

I think they are thread chasing dials (and at a guess from a metric lathe) but why the numbers are the same I don't know. My only thought is that for multiples of 5 tpi threads you can go on any of the 5 marks and similarly for threads that are multiples of 7 tpi.
If you know the leadscrew pitch of the lathe they are from, that might help see whether that is true or not.

Michael

Thanks Michael. The school disposed of the lathe years ago, and nobody can remember what it was. Apparently it was a fairly large lathe (larger than a Hercus). I don’t know what lathes they were putting in VIC schools in the 70s.

Which one has what tooth count?

Is it possible that they are for chasing diametral pitch worms and module worms?

Originally Posted by SurfinNev

Which one has what tooth count?

Upon closer inspection, it's 33 not 38. It wasn't cleanly stamped.

33 teeth on the dial with the 5's
35 teeth on the dial with the 7's

This is a diagram taken from a metric H&F 'educational lathe'. There looks to be a typo or two, but you can see a gear for 7.0mm pitch (and fractions of) and 5.0mm (and fractions of). Based on this table, the lathe probably has a another gear for the other stuff that was the one attached to the lathe when it was moved on.
Lathe table.png
I am guessing that someone has been clever and worked out that the gearing for the lathe means that anytime one of the 5 marks or 7 marks is next to the mark on the block, the screw can be engaged - in which case, why bother with the numbers?

Michael

Thanks Michael. You could be right. But why bother with two or more interchangeable gear/dial assemblies when the stacked gear theading dial like the one shown has been around forever?

Michael

Here is a similar setup https://bbs.homeshopmachinist.net/fo...ons-what-gives same confusion.

Originally Posted by lamestllama

Here is a similar setup..

Thanks for the link. At least that one is numbered 1 to 5, so it resembles an normal thread chasing dial. And mine almost certainly aren't home made. The number stamping is near perfect.

I guess I'll never know.