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Helical gear cutting

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gbritnell:
First off let me give total credit for the design and development of the helical gear cutting fixture to Chuck Fellows.
When first published he was making gears for a hit and miss engine. As his drawings were published on HMEM and some of the readers on this forum said they had to log into that forum to see threads I will copy them to this thread. For those of you that visit both forums just do a search for: helical gear cutter by cfellows.

The fixture itself is fairly simple. It consists of a body, spindle, index plate and cam follower. The body is bored to a nice fit for whatever size spindle you choose. Mine is .50 drill rod. I have cut some fairly large helical gears for model work with no chatter with this size spindle. On the holding end is a reamed hole with set screw for holding arbors to mount the gear blanks. (mine is .375) On the working end of the spindle is a boss, 1.00 diameter with a knurled flange with holes that correspond with the rows of holes in the index plate. This shouldered boss is free to rotate on the spindle. Attached to the spindle and is the index plate. This corresponds with the number of teeth you will be cutting. A pin locates the index plate to the shouldered boss. Onto the shouldered boss you mount a cylinder created by cutting a triangle of thin metal (I make mine from brass) (easier to form) This cylinder represents the lead of the helix of the gear. The cylinder runs against the cam follower to give the helical advance when cutting the gear teeth.
Here are some pictures of my fixture and some of the gears I made for my Fordillac flathead V-8 engine.
First the fixture and cutting a gear.

 

gbritnell:
This photo is of the cutter. It's made from W-1 drill rod and has the required profile for cutting the pitch and helix of the desired gear.

gbritnell:
Here's a picture of the brass template. I cut it on the bandsaw then milled it to the proper angle. I'm checking it with my sine plate and indicator. The second photo shows the annealed template being rolled around a rod to form the cylindrical shape.

gbritnell:
With helical gears if you cut two of the same gears they will operate at right angles to each other. If you need gears that have parallel axis then you need to cut a left and a right gear which requires two templates.
For my flathead engine I needed 2 parallel gears and and 4 right angle gears.

gbritnell:
Here is a video clip of cutting a helical gear for my inline 300 six engine.
http://www.youtube.com/watch?v=blaZ5tz0_6E

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