Gear module for Imperial gears

[mynewviceroy]

In trying to sort out replacement gears to enable me to cut threads, I've started playing with 3D printing my own gears (only for light home / hobby use). I have the drawings for the gears from this forum but I don't necessarily understand all of the terms, or not all of the terms are the same with the gear creating software I'm using.

I know the pressure angle is 20 degrees - that I can enter into the gear creator software - but what is the module number? Is it the same for all of the imperial gears or will it change with each gear, so does a 32T gear have a different module to a 80T gear? I've read on here that module figures of 1 or 1.5 are used but this think these refer to metric threads and my Viceroy is imperial (though I do think / understand with the correct gear combo (using 127T?) it can cut metric threads).

So TL:DR - what is the module number for a 32T gear?
Cheers, Phil

[mynewviceroy]

From playing with various calculators and on-line design tools, I think the module is 1.5 for my gear set. I've measured my existing 36T gear and it comes out at 53.78, so allowing for a bit of wear, call it 54mm. 54/36 = 1.5, so I'm going to put that into my gear CAD tool, generate the .stl then print that and see if that works.

[rpwilson]

I could be wrong (it has been known!) but my memory from when I was cutting gears for my Denford Synchro, is that they were 18 DP (or might have been 16DP), but certainly not modular.

Richard

[mynewviceroy]

Thanks Richard,

You are certainly not wrong. I've been reading various bits and pieces since my last post and I now understand that Metric gears have module numbers and Imperial gears have DP - Diametrical Pitch. It threw me initially as I knew from the drawings that I need 18DP gears, but the online CAD generators had a space for a Module number so I (in error) thought that there must be a conversion factor to change a DP to a module - turn out not to be the case (or at least I now know I can generate DP gears in Fusion360). Cheers!

Edited to say - I've just found out, you can convert Module to DP - 18DP is 1.4111 - https://khkgears.net/new/gear_knowledge ... ation.html

Every day is a school day for me at the moment - lots of new things to learn!

[Pete.]

As you've discovered, module and DP are just two ways of sizing involute gears depending on if they are sized in inches or metric. If you want an excellent conversion table you can get one from Davall Gear called "CONVERSION DP to CP to MOD.pdf". I can't seem to find it online now but it used to be free to download on their website.

There is another great resource you should get. Download a free program called gearDXF from Forest Moon Productions. It can not only produce DXF files of gears but can now output STL files for 3d printing plus you can type in the module size or the DP size and it will adjust the other on the fly. A very handy and well thought out program and it's free.

http://www.forestmoon.com/Software/GearDXF/

[mynewviceroy]

Thanks Pete,

I've downloaded it and have used it to generate a 80T transfer gear which I'm just 3D printing now.

Here's the result of last nights 3D print for an 80T change gear. I thought that the 4 additional holes might a. reduce printing time as less material, b. help to transfer forces around the plastic (no theory behind this just wild guess) and c. use less 3D filament.

80T Change Gear 3D printed in PLA

80T PLA.jpg (23.86 KiB) Viewed 5187 times

Having used the program Pete posted above and sliced it via Cura slicer, I now know that a plain gear vs a gear with 4 holes takes about 2 mins longer and uses about £0.02 more filament - so the holes are not work worrying about for a. and c. - but I have no knowledge if they help or not with b.