Dividing And Indexing Head Project

Mark_f

Registered
Registered
Joined
Jan 16, 2020
Messages
5
A while back, I built an indexing head from aluminum and steel. While not an extremely heavy duty device (which it was not intended to be) it works well. BUT, I have decided to build a dividing/indexing head from steel as a more advanced and heavier duty unit. I would like to use a worm wheel and gear,but the price is just too high to buy them. I have seen some units made using a straight tooth gear such as a change gear in place of the worm wheel. I like this idea for cost and flexibility reasons but how do you make a worm to run the straight tooth gear. Does anyone have any insight into this?
 
A while back, I built an indexing head from aluminum and steel. While not an extremely heavy duty device (which it was not intended to be) it works well. BUT, I have decided to build a dividing/indexing head from steel as a more advanced and heavier duty unit. I would like to use a worm wheel and gear,but the price is just too high to buy them. I have seen some units made using a straight tooth gear such as a change gear in place of the worm wheel. I like this idea for cost and flexibility reasons but how do you make a worm to run the straight tooth gear. Does anyone have any insight into this?
I think that the angle between the plane of the gear and the axis of the worm has to equal the lead angle of the worm. Thus your worm shaft does not come out quite at right angles to the gear shaft.
 
I think that the angle between the plane of the gear and the axis of the worm has to equal the lead angle of the worm. Thus your worm shaft does not come out quite at right angles to the gear shaft.

You lost me at the bakery. I have no idea what that means, but thank you.



Edit: ooooh oooh , wait, I think I know what you mean. the shaft and worm won't be 90 degrees with the gear, right?
In all the photos I seen of these, they appear to be 90 degrees.
 
Last edited by a moderator:
You lost me at the bakery. I have no idea what that means, but thank you.
Visualize a screw. Notice that the threads are not quite at right angles to the axis of the screw. That difference is the lead angle. Now imagine engaging those threads with the teeth of a matching straight tooth gear. The threads will now be parallel to the teeth of the gear and so the axis of the screw will not be parallel to the face of the gear but at a slight angle to it. That angle will equal the lead angle of the screw. The screw is your worm.
 
I believe what John was saying is that if your worm gear axis is angled relative to the straight gear teeth to match the helix angle of the worm's teeth you can pretty much drive the straight spur gear.

Have you considered buying a small reduction drive gear box and using the gears, bearings, body... from that. We have a surplus place here in Manchester, NH that has a shelf full of them for pretty cheap money. Probably a lot cheaper than buying the worm and gears new. And it wouldn't likely be 40:1.
 
I believe what John was saying is that if your worm gear axis is angled relative to the straight gear teeth to match the helix angle of the worm's teeth you can pretty much drive the straight spur gear.

Have you considered buying a small reduction drive gear box and using the gears, bearings, body... from that. We have a surplus place here in Manchester, NH that has a shelf full of them for pretty cheap money. Probably a lot cheaper than buying the worm and gears new. And it wouldn't likely be 40:1.

I finally figured out what john was saying. To me not being at right angle is a slight problem. More cosmetically than a functional issue.

I believe any ratio can be successfully used if you design the plates around the ratio you use. I could be wrong as Dividing heads always baffled me. I believe 40:1 is the standard, but I have seen other ratios.

i am still working on understanding the plates and the setups.
 
I believe what John was saying is that if your worm gear axis is angled relative to the straight gear teeth to match the helix angle of the worm's teeth you can pretty much drive the straight spur gear.

Have you considered buying a small reduction drive gear box and using the gears, bearings, body... from that. We have a surplus place here in Manchester, NH that has a shelf full of them for pretty cheap money. Probably a lot cheaper than buying the worm and gears new. And it wouldn't likely be 40:1.
The helix angle references the axis of the worm. It's the complement of the lead angle, which references a plane perpendicular to the axis of the worm. The angle between the worm axis and the spur gear axis would be the helix angle.
 
If I figured this out correctly. It would take 40 turns of the crank to turn the spindle once And you have a plate with various hole patterns of different numbers. You select a plate with the pattern of holes to to equal the distance in degrees the handle gets turned to give you the correct divisions on the spindle. Am I in the neighborhood here?

So , if you used a 30:1 set of gears, you have to figure the hole patterns to do the same job with the new ratio, correct?
 
Mark hope this makes sense

to make a very simple worm gear and wheel all you do is cut a disc mount it on the lathe compound so that it will spin freely but snugly and put a spiral flute tap in the chuck and move the compound against the spinning tap it will spin the disc cutting the tpi on it and then you use a bolt the same thread as the tap. It works very well and makes a very nice worm wheel and worm.
tomh
 
You lost me at the bakery. I have no idea what that means, but thank you.



Edit: ooooh oooh , wait, I think I know what you mean. the shaft and worm won't be 90 degrees with the gear, right?
In all the photos I seen of these, they appear to be 90 degrees.
Most worm drives have the teeth of the gear angled at the lead angle of the worm.
 
Back
Top