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Adjustable worm gear

Machdaddy

Plastic
Joined
Dec 21, 2017
I ran across something I've never seen before, an adjustable worm gear.Gear is split down the middle and a cam does the adjusting.
This was in a dividing head I was assesing!IMG_0593.jpgIMG_0594 (1).jpgIMG_0595 (1).jpg
 
Looks to me like this was just to remove any play from the engagement with the worm.
That would be appropriate for an installation requiring maximum accuracy and zero backlash.

- Leigh
 
how does the "cam" work? is there an excenter on the screw your showing?
 
I ran across something I've never seen before, an adjustable worm gear.Gear is split down the middle and a cam does the adjusting.
Had a cone drive gearset in a hobber done the same way, but the better way to do that is with a dualead (r) worm. The worm is ground with a slightly different lead on the two sides of the tooth, so that it gets fatter along the axis. Then you just move the worm along the axis to take up backlash. The split kind only has half a tooth in contact, where dualead (r), Gould & Eberhardt, 18-something, still has the entire face of the wormgear in contact.
 
That looks like a sharp edge also.... I know it may be softer than the worm, but......
 
B&S from 135 years ago had an indexing-dividing head with a split worm wheel for wear-backlash adjustment. The worm wheel is hidden behind a cover so the adjustment is obscured. The heads that I have seen usually have some Rube-Goldberg device attached to clamp the quill in place.
Here is a line drawing of the head. The split worm wheel is at the back of the head just above the worm.
Early 1882 Dividing Head with adjustable worm wheel.jpg
This is the mill the head was paired with.
1882 B&S Universal Mill and dividing head.jpg
John
 
What is the brand and description of the head please.

In tabulating machines (Paper shuffling in old gov't office machines) I've seen regular involute gears in two mating pieces like that with a spring arcing in a cutout between them, so that the gears are constantly in contact with both sides of the mating gears teeth at all times. I'm sure it only works with very lightly loaded gear sets.
 
What is the brand and description of the head please.

In tabulating machines (Paper shuffling in old gov't office machines) I've seen regular involute gears in two mating pieces like that with a spring arcing in a cutout between them, so that the gears are constantly in contact with both sides of the mating gears teeth at all times. I'm sure it only works with very lightly loaded gear sets.

Lots of dual overhead cam engines have just such an arrangement to take the backlash out between the two cam gears to decrease noise. They run hundreds of thousands of miles without undue wear.
 








 
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