Bilgram Bevel Gear Attachment

[Benjamin Roth]

I know, yet another thread on Bilgram's machine.

Is there a reason for an adjustment on the attachment for cutting the root angle other than ease of set-up? Could you just set the angle on the slotting attachment for the root so long as the tool plane passed through the pitch cone apex? Building such a machine would be a lot easier without having to make all the extra parts for the root setting.



Picture is from lathe.co.uk

 

[johnoder]

The only reason for the existence of Bilgram is that it GENERATES tooth flank involute - no involute form tool required

This fact makes it necessary to adjust angle WITHIN the mechanism of the attachment, and never external to it.

ALL the Bilgram tool movements aim at the apex of the partial cone element you can see there

And by the way - ideally, a DIFFERENT partial cone for EVERY pitch cone angle you want to cut

If you like, study up on Hugo Bilgram's related patents

 

[IrbyJones]

That should work in the setup pictured. You'd have to rotate the slotting attachment and adjust it vertically so, as you said, "the tool plane passed through the pitch cone apex." But you have to do the vertical adjustment anyway on this setup. You're right, it would make the mechanics of the bevel gear attachment easier if you already had the slotting attachment. Bilgram had to include the gimbal for the root angle adjustment because his shaper ram direction was fixed - as you surmised.

BTW, thanks for pointing this attachment out. I had never seen one like it.

Irby

 

[IrbyJones]

To clarify what I think Benjamin is suggesting:

Here's Bilgram's original patent figure.

The base and shaper mechanism are fixed, and to set the tooth root angle, the deck of the machine that supports the X-X plane, and all the mechanics to the right of the shaper ram and cutting tool in this figure, is tilted clockwise about point O, which is the apex of the rolling cone.

What Benjamin is suggesting is to essentially fix the X-X plane, and all the mechanics to the right of the shaper ram and cutting tool, and tilt the shaper ram and it's supporting structure instead. The Bevel Gear Attachment for the Riva mill has an outer gimbal that serves to adjust the path of the cutting tool as it cuts the tooth root, just like in Bilgram's later designs. The axis of that gimbal is in/out of the paper at point O. As far as the gimbal axis is concerned it doesn't matter which side is rotated (and then locked in that position).

Irby

 

[enginebill]

I could use one of those, thanks for posting.

 

[Benjamin Roth]

Yes, that is correct. Thanks for the providing a better explanation, Irby.

I appreciate the input. I wanted to make sure I wasn't overlooking something. I have contemplated building a similar attachment and simplifying the project makes it more appealing.