A Modified Indexer for the Unimat

Ronald E. Thompson
Copyright 8-22-2011

This is an original Unimat indexer and 3 jaw chuck. The index plates (gears) are made by me and sold here:


The problem is they aren't made any more, and they are getting scarce and expensive. I considered making the main body to sell, but the index pin is intricate and has many small parts.
It would be hard to make a profit if my time was to be worth anything. And then there is the fact that a full set of index plates was costly, as well.

In talking with other people on the Unimat Yahoo group, an idea was born. Why not eliminate the expensive parts, and create a new screw drive?
The idea is to make it work like a rotary table, but retain the size of the work envelope and the ability to use other Unimat parts, like the 3 jaw chuck and the round t-slot table.
Below is the inital concept rendered in Solidworks.


This was close, but not quite there. It still needed a way to take up the lash in the worm gear, and a way to indicate the amount of rotation of the input shaft. Below is a more refined concept. The casting would be cut with a bandsaw or slitting saw to separate the worm carrier so it could be adjusted and the input shaft now has an indicator ring.

This all sounds good, but a prototype needs to be made to prove the concept. Larry Collier of Lexington Kentucky works for a company that has a 3D printer and offered to make a 3D printed plastic model from the Solidworks model. I made the changes needed to make it into a casting pattern and Larry gratiously printed it and shipped it to me free of charge. You can click on a photo below to see a much larger version.

I was concerned the 3D plastic model would show ridges that would make it impossible to pull from the casting sand without destroying the sand mold. 
While there are some ridges, I think it's smooth enough to work as a pattern.

That's all for now. I hope to cast one or two soon.

Visit my main page here: Plansandprojects.com