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Cutting a worm?

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Graham Rounce21/05/2019 17:42:55
28 forum posts
2 photos

Yes, that's why I was thinking of square-profile threads, which should cause very little up/down bending of the screws? At the expense of more friction, maybe.

Talking of which, Paul Lousick, where can you get round rod threaded with a square profile thread? I hope you didn't mean "square rod", like a rack?

SillyOldDuffer21/05/2019 18:33:22
4601 forum posts
988 photos

Have you tried searching for ACME threaded rod Graham? Now that 3d printing is popular it's quite cheap in 8mm, 10mm and 12mm diameters. Here's an 8mm on ebay, £4.19 for 300mm long. (ACME is easier to make than true square and much more common.)

Michael Gilligan21/05/2019 19:04:25
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13827 forum posts
603 photos
Posted by SillyOldDuffer on 21/05/2019 18:33:22:

Have you tried searching for ACME threaded rod Graham? Now that 3d printing is popular it's quite cheap in 8mm, 10mm and 12mm diameters.

.

< Pedant Alert >

ACME threaded rod is not a metric standard [whatever is advertised on ebay] ... The metric equivalent is called Trapezoidal.

MichaelG.

Andrew Johnston21/05/2019 19:08:39
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4786 forum posts
538 photos
Posted by Graham Rounce on 21/05/2019 17:42:55:

Yes, that's why I was thinking of square-profile threads, which should cause very little up/down bending of the screws?

For a small worm wheel you'll have significant undercut of the teeth to mate with a square thread so the teeth are likely to break in bending instead.

Square threads are almost obsolete for good reason. They have three interference possibilities all of which are independent.

Andrew

SillyOldDuffer21/05/2019 20:39:31
4601 forum posts
988 photos
Posted by Michael Gilligan on 21/05/2019 19:04:25:
Posted by SillyOldDuffer on 21/05/2019 18:33:22:

Have you tried searching for ACME threaded rod Graham? Now that 3d printing is popular it's quite cheap in 8mm, 10mm and 12mm diameters.

.

< Pedant Alert >

ACME threaded rod is not a metric standard [whatever is advertised on ebay] ... The metric equivalent is called Trapezoidal.

MichaelG.

Gosh that burns! Good spot though - searching for 'trapezoidal' finds even more rods.

Michael Gilligan21/05/2019 22:27:33
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13827 forum posts
603 photos
Posted by SillyOldDuffer on 21/05/2019 20:39:31:

Gosh that burns! Good spot though - searching for 'trapezoidal' finds even more rods.

.

The worst of it, Dave, is that the link you posted claims 8mm ACME threaded rod, and a T8 nut to fit.

29° / 30° ... Who cares ?

crying 2 MichaelG.

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