Involute cutters

Hi & Merry Xmas.

This is a question about gear cutting. I want to cut my own gears for the first time. The plans says 8 DP with a pressure angle of 20 degrees. At the moment I can only find 14 1/2 degree cutters at a reasonable price. So can I use them with a bit of recalculation. Also, I've worked out that 8 DP is = to Module 3.175 is my calculation right.

Thanks

Garry

Provided you cut all your traction engine gears to the same pa there is no problem and they will  look a bit more like the older more pointed teeth of the original so 14.5 pa will be OK.

The only time it would pay to stick with 14.5pa is if you have a sprung rear axle in which case the gears will stay in better mesh with this profile.

Yes your maths is right but as 3MOD is the closest cutter size you can buy you will have to alter PCD and tooth count to make them fit.

Edited By JasonB on 25/12/2018 08:53:39

Make your own cutters? The mike's workshop site is helpful.

Thanks Jason, I think I will now go ahead and order a set of 8 DP 14 1/2 degree cutters. That info about the look of the teeth was helpful. And the rear axle is sprung. Thanks again for the help.

Garry

None of the basic parameters such as pitch circle diameter, circular pitch and tooth depth are affected by the pressure angle. So there is no need to do any calculations when changing between 20PA and 14.5PA. A pressure angle of 14.5PA is more prototypical, although I’ve chosen 20PA for all my traction engine gears.

As Jason says changing to an integer Mod value will be a nightmare. You’ll end up redesigning half the engine.

I’d be slightly cautious about cheap cutter sets. I bought some cheap cutters when I was playing with helical gears, but I wouldn’t want to use them for proper gears due to eccentricity and wobble issues, in some cases.

Cutting gears is very satisfying:

Andrew

Pressure angle is not a problem, but if you change from 8dp. All the gear centres will need to be adjusted, so as Andrew says, a big redesign needed