What might this worm gear fit?

Where do you want 40:1 reduction of the speed of a shaft? The size of the gear will, of course, determine the amount of power that can be delivered by the size gear.

-- Why do penguins walk so far to get to their nesting grounds?

Well ... the 40:1 ratio is a common one found in index/dividing heads, so if you want to make an very good one, that might be an excellent starting point. Most people who want to build their own dividing head are scared off by the prices from Boston Gear.

What is the OD of the big gear, and the ID as well? It might have to be bored out a bit to allow a reasonable spindle to pass through it.

Enjoy, DoN.

I'd thought that making a dividing head with it would be an interesting project (for sometime in the unforseeable future), but also that if someone had a machine down for want of this gear it might find a better use.

OD is 4 1/2", and 7/8" thick. ID is 3/4" with 1/8"x3/16" keyway.

It's probably a standard 10 pitch 40T worm gear. In order to be sure of the ratio you need to check whether the worm is a single or multiple start, though in the photo they appear to be single start.

Search Boston Gear's online catalogs for more info.

Ned Simmons

A kind thought.

O.K. The size is reasonable for a nice dividing head, but the bore is too small. That size dividing head would probably want a spindle which could mount something like a #3 Morse Taper -- or a similar sized B&S (I think that is a B&S #9). If making from scratch, I would suggest going for the Morse taper -- or perhaps making it to fit a common collet size. Make the spindle with a external thread to mount a common chuck size as well.

You *would* have to bore the gear and cut a new keyway to fit any of these spindle options -- but it looks as though there is a lot of meat in the hub.

Enjoy, DoN.