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Hobbing Gears with a Mill

magno_grail

Cast Iron
Joined
May 29, 2014
Location
ca, US
Making a new gearbox for a BSA motorcycle. I have found involute DP10 cutter sets in PA14.5, need PA20. DP10 PA20 cutters are ten times the price of PA14.5. DP10 PA20 hobbs are available. Has anyone tried cutting gears on a CNC mill using a hobb? Obviously, the Z and X movements have to be coordinated and the spindle speed has to be slow for the X axis to keep up. I am also not sure the spindle has enough power at those speeds - '91 VF-1.
Another option is to rotate the A axis and keep the Z axis constant but I do not think a 5C rotary can turn fast enough.
Some gears are being cut with M2.5 (DP10.16) cutters but with the ratios selected the pressure angle gets too far away from 20 degrees to use it for all of them.
I have 3D printed the gears and now want to make them in aluminum before cutting the steel versions.
Thanks.
 

wmpy

Hot Rolled
Joined
Dec 16, 2011
I don't know much about gears and gear cutting, but if trying to use your rotary to hob the teeth, don't you need to synchronize the rotation of your spindle to the rotation of the A axis? Does your VMC have the ability to do this? Can any VMC do this?
 

magno_grail

Cast Iron
Joined
May 29, 2014
Location
ca, US
Moving Z with X would do the same thing as tilting the Z axis or inclining the rotary to the X axis.
Talking to the shop that makes my parts, they said the spindle speed is not accurate enough to be able to match it to the rotary.
Found a solution though, Maxwell Tools in India has DP cutters at a reasonable price, $25 each. The ones listed on Ebay were sourced from India so I thought it better to go to the source rather than a supplier.
 

wmpy

Hot Rolled
Joined
Dec 16, 2011
Please post photos or a video of your setup if you get this running. I'd like to see it.
 

hvnlymachining

Cast Iron
Joined
Jun 21, 2019
Location
St.Onge
Hobbing requires perfect timing and a lot of torque simultaneously. As well as a very rigid setup. Involute cutters are much simpler and much quicker on a mill. I've made quite a few on BP clones.

Keep the cutters flooded with coolant if possible.

Happy machining!
 








 
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