GearHeads Forum

Actually, i'm just happy i understand the word "octoid" now.

Out of those 5 theorems, they lost me at the first. 
Cheers Damo

Hi Art, I tried to draw what I meant. Sort of looks like a potato chip. The line passes through 2 sets of axes at the same angle. From the side it looks like a figure 8. Imagine the rack going around the circumference and 2 opposite tooth flanks are on the surface.
Cheers Damo

Not sure if this ...

I think all the calculations for a stanard involute are correct, just have to do one more function to them. Imagine a spur gear and the flat plane on the side of the spur gear, now all of a sudden that flat plane is spherical? Image the teeth. They are still an involute, just the world they live in ...

Hi Alf, yes i think you're right. If you get a straight rack and project onto a sphere you will get 2 crown gears. But what happens to the tooth form when you get closer to the centre? This is where the octoid comes in. If you take one tooth flank of that crown gear, and another flank on the ...

Actually, I like this book, goes into the cutting tool manufacture in detail.

http://books.google.com.au/books?id=wZpaPKcQZxAC&pg=PT697&lpg=PT697&dq=octoidal+vs+involute&source=bl&ots=eN-tM7kbAd&sig=1eRWxY8froShIFqViarBfY6NmHQ&hl=en&sa=X&ei=haOmUuL4E4WfkAXKk4CoCw&ved=0CGUQ6AEwCTgK#v=onepage&q ...

This link is about the best definition of an octoidal tooth form that sort of makes sense.

http://books.google.com.au/books?id=IAE5t4OD03YC&pg=PA253&lpg=PA253&dq=octoidal+vs+involute&source=bl&ots=mHykSDR8gO&sig=b28Mfj8V2WpXuIPwC3hmknkPoMM&hl=en&sa=X&ei=haOmUuL4E4WfkAXKk4CoCw&ved=0CEkQ6AEwBDgK#v ...

I'm not sure I get what you mean about the spiral generator Art.

At the moment, this is how I intent to make the spiral bevels; (My machine is horizontal, it has a rotary pallet and a rotary table on top of that)

1. In my CAD, draw the helix geometry on the root cone, the start of the helix is at ...

It's a very interesting subject. I have a need to produces some spiral bevel so will continue investigating. What is also worth noting is that in literature describing setting up spiral bevels correctly, the tooth contact area should be checked and made sure that it is in the middle of the tooth ...

Hi Art, I agree it's hard to find a definate understanding of the octoidal tooth form but it is what I have been trying to understand from reading various papers on the web, but am not exactly sure. Maybe I am not understanding it correctly, most papers do seem a bit vague but talk about the form ...