How to do 100 divisions

[steamdaveParticipant @steamdave]

For new handwheels

[steamdaveParticipant @steamdave]

I want to replace the handwheels on my Myford S7 with the GHT design. What is a suitable way to make the 100 divisions on a gear box equipped S7? I don't have a dividing head that fits on the lathe.

Dave
The Emerald Isle

[Howard LewisParticipant @howardlewis46836]

Suggested by someone else, so not original suggestion is:

Fix a 50T gear to the mandrel.

Hold the embryo dial on an arbor in the chuck.

Make up a detent to be a tight fit between the teeth,

While you are about it, make up another that locates symmetrically on the flanks of the tooth

Use one detent to position the dial, to make 50 marks.

Without disturbing anything else, fit the second detent into the holder.

Unlock the mandrel.

Locate the now unlocked mandrel, and make 50 more marks.

Hopefully, there will be 100 marks, equally spaced around you new dial.

Howard.

[Neil WyattModerator @neilwyatt]

It's easy to fit change gears to a plug in the back of the mandrel, I did this for my mini lathe, combined with a mandrel handle.

You can also make a detent in the form of a forked peg, which is what I did. One way it fits between teeth, the other it fits over a tooth.

[Roderick JenkinsParticipant @roderickjenkins93242]

OP says his lathe has gearbox…

[egaParticipant @ega]

Posted by Roderick Jenkins on 10/02/2020 17:15:09:

OP says his lathe has gearbox…

Presumably implying that he has no change gears that are accessible for this purpose they being, as Martin Cleeve would say, locked up in his gear box.

Obviously, the gear box would prevent the use of change gears if available.

[egaParticipant @ega]

Too late to edit; I meant to say would *not* prevent.

[jason udallParticipant @jasonudall57142]

Who ever put the "add posting button " tight to the terms and conditions link …not for the first time have I lost an erudite and illuminating post at the last herdal…

Back to point…. either

Take circumference by wrapping strip of paper

Divide this length with drafting techniques..transfer these divisions back to wheel.

Or

Turn wheel to have circumference yielding convenient division  

Or use cad to divided wheel and print paper strip.

Glue down and over varnish.

 

The latter works for me ..also get better contrast for my tired eyes.

 

Edited By jason udall on 10/02/2020 19:57:12

[steamdaveParticipant @steamdave]

Thanks for the suggestions.

I did wonder about using the paper stuck to wood idea, but I will spend the kids inheritance and get a 50 tooth change gear. (The kids don't want the lathe).  I like the idea of the forked detent.

Dave
The Emerald Isle

Edited By steamdave on 10/02/2020 21:34:53

[Roderick JenkinsParticipant @roderickjenkins93242]

In which case Dave, perhaps these pics will give some ideas:

Cheers,

Rod

[Jouke van der VeenParticipant @joukevanderveen72935]

You could take a thin strip of metal and drill 101 holes in it at equal distance. The distance between the holes is kept constant by using a gauge with two holes in it. The next drilling position is determined by a fixation pin in one hole of the gauge and through the last drilled hole in the strip.
After drilled 101 holes you bend the strip and fixate it first and last hole with a pin. Then you fill the circle with a piece of wood to make a wheel with 100 divisions. The wheel is attached with some kind of plug to the back of the head spindle like Neil described. You still need a pin that falls into the holes of the strip index the wheel.

Above described method is (was) used by clockmakers not having a proper division table for all kinds of “exotic” clock wheels.

[HopperParticipant @hopper]

You dont have to use a Myford gear. Just buy any cheap 100 tooth gear off ebay etc and make a arbor and detente plunger to suit. A module 1 gear would do the job.

[John HaineParticipant @johnhaine32865]

Or I could lend you a division plate…

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