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Involute tooth depth

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David Noble07/04/2021 14:34:38
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256 forum posts
11 photos

As all my gear cutting has been in clockmaking, I have been using cycloidal form gear teeth. I have one involute gear to make it is Mod 1 & 63 teeth. I would be grateful to know the full depth I ought to cut it.

Many Thanks, David

Howard Lewis07/04/2021 15:17:20
4866 forum posts
12 photos

If you use an Involute gear cutter, it is likely to be marked with the df number, which is the depth of cut.

If you intend to cut any more gears, Ivan Law's book on "Gears and Gear Cutting", No.17 in the Workshop Practice Series will be a good investment and a very useful guide and reference.

Howard

DC31k07/04/2021 15:26:28
480 forum posts
1 photos
Posted by Howard Lewis on 07/04/2021 15:17:20:

If you use an Involute gear cutter, it is likely to be marked with the df number, which is the depth of cut.

More usually referred to as d + f .

If you search for 'd + f gear' or 'whole depth of gear tooth', there is a lot of material available.

For metric gears, this one is good: https://khkgears.net/new/gear_knowledge/abcs_of_gears-b/basic_gear_terminology_calculation.html

For imperial gears (not your current challenge), this one is good: https://www.bostongear.com/-/media/Files/Literature/Brand/boston-gear/catalogs/p-1930-bg-sections/p-1930-bg_engineering-info-spur-gears.ashx

John Hinkley07/04/2021 15:57:58
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1117 forum posts
376 photos

David,

To answer your question directly, I used my go to gear generator software. It gave the following result for the quoted gear:

GearDXF screeenshot

In case it's not too easy to see from the above screenshot, the depth of cut works out as 65.0 - 60.5mm = 4.5mm. Or if you prefer, 0.177in.

John

David Noble07/04/2021 17:13:40
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256 forum posts
11 photos

Many thanks everyone. It's a change gear for my metric lathe so I can cut imperial threads.

David

Pete Rimmer07/04/2021 17:18:02
979 forum posts
57 photos
Posted by John Hinkley on 07/04/2021 15:57:58:

David,

To answer your question directly, I used my go to gear generator software. It gave the following result for the quoted gear:

GearDXF screeenshot

In case it's not too easy to see from the above screenshot, the depth of cut works out as 65.0 - 60.5mm = 4.5mm. Or if you prefer, 0.177in.

John

John, it's actually half of that.

Regards

Pete

David Noble07/04/2021 17:55:11
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256 forum posts
11 photos
Posted by Pete Rimmer on 07/04/2021 17:18:02:
Posted by John Hinkley on 07/04/2021 15:57:58:

David,

To answer your question directly, I used my go to gear generator software. It gave the following result for the quoted gear:

GearDXF screeenshot

In case it's not too easy to see from the above screenshot, the depth of cut works out as 65.0 - 60.5mm = 4.5mm. Or if you prefer, 0.177in.

John

John, it's actually half of that.

Regards

Pete

Thanks Pete, I had already 'read between the lines'

David

John Hinkley07/04/2021 19:06:14
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1117 forum posts
376 photos
Posted by Pete Rimmer on 07/04/2021 17:18:02:

John, it's actually half of that.

Regards

Pete

Well spotted, Pete. Should have been obvious, really. I thouht it was a bit deep at the time, but failed to apply what little common sense I have left!

John

not done it yet07/04/2021 19:12:18
5946 forum posts
20 photos

Good program. I would have expected the pressure angle to be given as 20 degrees, not 14.5.

Pete Rimmer07/04/2021 21:25:36
979 forum posts
57 photos
Posted by not done it yet on 07/04/2021 19:12:18:

Good program. I would have expected the pressure angle to be given as 20 degrees, not 14.5.

You can specify but for the purpose it wouldn't matter, the whole depth is the same for both.

Howard Lewis08/04/2021 19:56:38
4866 forum posts
12 photos

I would have expected module gears to be 20 degrees pressure angle.

You are obviously thinking of a 63T gear.

They are available for mini lathes.(Arc Euro sell aluminium ones ) Using a 63T gear in the train will not be an absolutely precise (You need a 127T for that, but a 1 Mod gear will be big - 129 mm diameter! )

For most purposes, the errors with a 63T gear will be tolerable.

Howard

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