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Machining a helical gear

Mike Gre

Plastic
Joined
Jan 8, 2017
I have a 3k K&T universal mill. I have a dividing head that I have rigged a stepper motor to that with the help of an Arduino cuts spur gears with a hob based on an encoder on the spindle. I have used this for years and created many good spur gears. If I rotate the table to the lead angle of a helical gear and then run the hob the same way I do for a spur gear, will I get a helical gear? Most people I have seen cutting a helical gear on a regular mill are running the dividing head off the x axis leads screw but with a standard gear cutter and not a hob?
 

Dr. Rob

Hot Rolled
Joined
Nov 25, 2002
Location
Sweden
”…If I rotate the table to the lead angle…”

Taking a chance by posting before having morning coffee here, but I would say no.
But, if you swivel the dividing head to the lead angle of your desired helical gear, then yes.
So, table angle = direction of travel = lead angle of hob. Always.
Dividing head = lead angle of desired gear

Beyond that, some additional math to figure out the size of the gear blank (diameter increases with increased helix angle) and you’ll be on the right track. It sounds like you know what you are doing; you’ll figure it out. Good luck.

.
 
Last edited:

Mike Gre

Plastic
Joined
Jan 8, 2017
Thanks,
I will have to give that a try and see what I come up with. I have lots of books on gears but very few of them have anything to say about hobbing on a conventional knee mill.
 








 
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