bevel gear calculation question

[strokersix]

I have a straight bevel gear design, 13/45 tooth 2 module using Dudley's "Handbook of Practical Gear Design". Standard calculations are based on large end of the gear.

I wish to produce approximate gears using the parallel depth method. I have altered the face width so the small end matches 1.5 module. With reference to Ivan Law page 106, I calculate the cutters to use are for 121 teeth #2 cutter for the gear and 10 teeth for the pinion. Standard cutter #8 is for 12-13 teeth. Should I use a #8 cutter for the pinion? Perhaps tip relief might allow this to work? I'll be deburring these by hand anyway so a little hand fitting is acceptable to me.

It seems 13 tooth pinion in a 13/45 ratio may be outside the range of parallel depth method.

These power transmission gears will be grease lubricated nylon and as such will be a little more tolerant of error than steel gears.

 

[strokersix]

http://i965.photobucket.com/albums/a...x/DSCN3757.jpg

I used #2 and #8 cutters. I can see a little too much curvature at the large end of the pinion. Small ends look pretty good and they do roll smoothly in my hands. Next step is to run them and see what happens.

Question: I would like to trade some tooth thickness from gear to pinion. I can thin the gear teeth no problem but I can't thicken the pinion teeth because the cutter fills the space. I saw somewhere that bevel gear milling cutters may be available with thinner section for this purpose. Can anyone tell me a source for such a thing? Or am I on my own with a single point cutter?

Thanks.

 

[strokersix]

 

[MikeHalloran]

How about a brass pinion?



Mike Halloran
Pembroke Pines, FL, USA

 

[strokersix]

Thanks Mike but that's not what I'm after.

This is preliminary test hardware to develop a production design. Production intent is injection molded.

I am sourcing properly cut bevels with tooth thicknesses adjusted to balance strength for test.

My parallel depth effort above is a fall-back plan if that source can't meet required delivery time for test. Parallel depth approximate gears are better than no gears. According to my calculations these are roughly 1/2 as strong as properly cut and thickness balanced gears. I think I can improve on that by trading tooth thickness from gear to pinion. But I need a thinner cutter to do it.

Maybe I can alter a standard cutter to do this by removing one side of the involute. I need to take a cut down each side of each tooth. Flip the cutter between cuts and I think that might work.