1/2" thick aluminum gear blank with 1" ID.
I used my 10" radial arm
saw equipped with an 80 tooth carbide tipped metal cutting blade to rough
gear blank. I then turned and bored the blank to the needed dimensions on the 9x lathe.
The blank for my 180 tooth gear has an OD of 5.865 ( Pitch diameter is 5.729")
To Calculate Worm Blank OD
This is the tricky part.......
I'm not going to go into much detail because I don't know that much about
Possibly someone with some experience in this area can help correct me.
These calculations are just from my experience hobbing gears which I will remind you is very little.
There are gear calculators available such as WM Bergs GearSpec V.1.3 , This is a free download
that you can download here. With this program you can calculate the worm gear dimensions if you
know the pitch of the worm to be used. This is a problem since Diametral Pitch and TPI ( threads per
inch ) are not the same. However from what I have come up with a Diametral Pitch of 1/10 worm thread
it very close to 10 tpi. ( Actually works out that a 1/10 Diametral Pitch is approx 10.2 tpi ) Someone correct
me if I am wrong here. It also depends on the pressure angle of the worm thread.
A 20 tpi bolt thread is very close to a 64 pitch gear ( works out to 20.4 tpi )
So to sum it up the GearSpec program will not get you exact dimensions unless you use a standard
pitched worm such as a 16 , 32 , 48 , 64 ,ect Diametral Pitch. To purchase the worms can get expensive
and you would have to purchase an extra one to make a cutter.
Using my Grizzly mini mill and dividing head I notched or indexed the gear blank to the
correct tooth count. Here I used a dovetail cutter to do the notching. I also set
the dividing head to a 4 degree angle to match the cutter.
I just "eyeball" the depth , be careful not to cut too deep.
Notching / indexing finished and ready for hobbing.
Click below for more details
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