I’m looking for custom 20-tooth gears that would fit with tetrix gears, but can’t seem to find anything. I found some information about general specs of the gears on these forums:
“TETRIX gears have a diametral pitch (DP) of 32 teeth/in, a pressure angle (PA) of 20 degrees, and a face width of 0.250 in” - Nate Laverdure.
I tried Amazon and a few smaller sites and can’t find anything. I would just CAD it and try seeing how it holds up 3D printed, but I’m not too great with CADing custom parts, especially not gears with details specifications like that.
In metal, for 32dp, 20 degree PA, .25" face width, SDP-SI has 18 and 24 tooth gears, but not 20. Fortunately if you’re willing to go a bit wider or a bit thinner, they do appear to have 20t gears that meet the OP’s requirements.
Also they have a far larger variety of gears with those specifications than Tetrix, so you can likely make your desired ratio work anyways, even if you want to stick with your exact requirements.
Something to think about is the bore that you want. I’d say that the reason 20t gears aren’t available from tetrix is that the typical FTC bolt pattern wouldn’t be able to fit onto the gear as a 20t 32DP gear is quite small. You will need to think carefully about what bore you need, as it might be difficult to integrate with the other parts of your mechanism.
If you are going to 3D print the gear, it would most likely be better to 3D print both the 20t and the gear that it is meshing with in a wider and most likely lower DP. A wider gear with a lower DP will reduce the likelihood of the teeth breaking.
If you need help designing the gear just send me a PM or reply.
If you relax the constraint on the thickness of the gear, you’ll find sources for most sizes of 32DP 20 degree pressure angle gears. Check SDP-SI, McMaster, etc. Finding one exactly 1/4" thick is going to be your biggest challenge.
McMaster has that gear available in brass or stainless steel in 3/16" face width, as well as steel in rod stock if you really need that extra 1/16" or more.
Tetrix gears are actually 0.8 Mod (31.75 DP) 20 PA. 32 DP is close enough for most things, but be aware it could affect your center distance. 0.8 Mod is common in rc parts so that may help your search. You may be able to source 20 tooth pinion wire. With a 20 tooth it won’t matter 32 DP or 0.8 Mod. Pinion wire is fast just bore and part off to length. Press it onto the shaft. You can also turn a shoulder for set screws if it needs to come apart later.
Before I bought a set of 0.8 module cutters I used 32 DP cutters and metric OD… this kept my center to center distance correct.
