Trying To Build Dividing Head

  • Thread starter Thread starter Lordbeezer
  • Start date Start date
Please don’t get me wrong. There is lots of pride and fun in making whatever yourself in the home shop! But, there is also lots of fun in hunting down a second hand factory made one as well!
 
Using a 1/2 X 20 tap to make a 40 to 1 ratio worm gear will result in a very small final gear less than 0.750.
Lets try a 1/2 X 13 tap.
1" divided by 13 = 0.077 per tooth
Number of teeth + 2 =42
42 times .077 = 3.231
3.231 is the circumference of your gear blank.
Divide 3.231 by 3.14 to get the diameter of 1.029"
This is still really small to work with so lets try an 11 tooth per inch example.
1 divided 11 =0.090 per tooth
42 teeth times 0.090 = 3.818
3.818 divided by 3.14 =1.215 " in diameter. Still fairly small.

In my case I wanted 90 teeth on the worm wheel which ended up at 2.254 in diameter.
If you want to stay with the 40 to 1 then I would look for a courser thread on the worm shaft to start with.

NOTE
In order to make exactly the number of teeth you want when cutting the blank you must gnash the blank at each place you want a tooth.
The cuts need not be deep (0.025 - 0.050) just a place for the tap to align with. Turn the tap by hand the first couple of rotations paying close attention that each cut slit is centered on the tap tooth. I made several worm wheels with different ODs trying to get the correct number of teeth without cutting the slits and never was able to one right.
Now for the next question how do you cut 40 gnashes around a blank accurately with out a rotary table or an indexer?
I don't know.

Have fun

Ray
 
Thank ya'll very much for your help..have a 50t and 80t gears.gonna make 2 10t..put then together per hmans post for my 40:1...hope it goes as simple as it sounds..if I wanted to make a worm wheel with 100t cut with a 5/8 X11 tap how big should my blank be.ended up with 105 with blank at 2.890..Thanks
 
I made my dividing head from the Gingery book. I bought some acme ready thread and used it to cut the worm gear. I cut some gashes in the ready thread and mounted it in the lathe between centers. I mounted the gear blank on a post on the compound slide. The ready thread cut the worm teeth. It worked like a hobbing process without power to the gear blank.
 
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I'll weigh in on this,

You can make a worm wheel for any thread pitch by making sure you have the right diameter on the wheel you want to cut. It just has to work out to 40 teeth at the pitch line.
That said, if you use a standard fastener thread, it will have a 30degree pressure angle. That tends to force the worm and wheel apart. An acme thread has a 14 and a half degree pressure angle, and much more force is transmitted to turning the wheel rather than forcing it apart. you want polished threads too. A rough worm will eat your bronze gear.
 
With google sketchup it is very easy to divide a circle into any number of equal divisions. Attached is a drawing that took me less than 5 minutes to create where I divided the circle into 40 equal divisions.

40 line circle.jpg
 
Thanks for the information.took a 50t driven by 10t driving a 8t turning a 64 t to get my 40:1..finished indexer today.going to use it for awhile then take apart and paint..thanks for everybody's help..Phil..I'll post pictures of my Fred flint stone special after paint
 
Quick note.was buying a few items from a retired machinist I showed him picture of indexer.he said he had a small one with foot from 20-30 years ago.never used it..bought it real quick..Dayton electric .made in Taiwan.looks real nice. Thanks

image.jpeg
 
I have just finished a dividing head shown in the June/July 2010 issue of the Machinist's Workshop it is easy to build and uses any gear for indexing. A worn indexing module is shown in the Oct/Nov 2010 issue it uses 3 gears and 1 index plate with 3 hole circles it will index most of the divisions that would be needed.
 
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