Helical gear cutting adventure, Chuck where are you?

[cfellows]

Interesting, George.  If you used the diameter to the outside of the template, 1.125", the angle comes out to 13.7, which is about 1.5 degrees less.  I guess the proper diameter to use is to the outside diameter.

The gears I have made were never small enough to show the error.  But I will change that calculation for future gears. 

By the way, nice video!  I really like the setup using a mill.

Chuck

[gbritnell]

Hi Chuck,
I'm going to make a brass helical template from .031 brass and see if it will give me a more accurate result. By that I mean I'm going to see if the distortion is reduced in the rolling process. I see no reason why 1/32 brass shouldn't be rigid enough to work. If need be a narrow strip could be cut and soft soldered onto the template just below the working edge to help stiffen it.
Just think how great is would be to hook up your Arduino rotary table to the mill leadscrew and machine the perfect helix. Just chuck up a piece of metal tubing and cut. No annealing, bending or hammering involved.
gbritnell

[cfellows]

Hi Chuck,
I'm going to make a brass helical template from .031 brass and see if it will give me a more accurate result. By that I mean I'm going to see if the distortion is reduced in the rolling process. I see no reason why 1/32 brass shouldn't be rigid enough to work. If need be a narrow strip could be cut and soft soldered onto the template just below the working edge to help stiffen it.
Just think how great is would be to hook up your Arduino rotary table to the mill leadscrew and machine the perfect helix. Just chuck up a piece of metal tubing and cut. No annealing, bending or hammering involved.
gbritnell

Aaah, I've been thinking about just that for some time now.  An arduino and stepper motor drive would lend itself nicely to the precision and wide disparity of ratios required for several different gear pitches, helix angles, and number of teeth.    What I've come up with so far is a lead screw with a quadrature encoder to provide the axial movement.  The encoder would be read by an Arduino which calculates the number of steps required and drive the stepper motor to spin the gear blank in sync with lead screw movement.  The whole thing is not a lot different in concept from a gear hobber.

The trick is to get the whole thing built into a nice little assembly that would fit in the mill vice or on a lathe bed.

Chuck