Dividing And Indexing Head Project

Sorry reread your question, please disregard the above.
My ADD, ADHD, dyslexia, senior moment all kicked in at once. o_O
I would like to know that would work as well.
Tomh
 
There is an article in HSM about fitting a worm drive to a mini lathe mounted indexer. The worm was to drive a module 1 gear - 20deg. pressure angle and tooth spacing approximately 1/8 inch. The lathe tool was ground to a 40deg angle instead of 60, and the threads cut at 8-TPI. The angle and TPI would have to be changed to match whatever gear you choose. While the best way to transmit power between a worm and a spur gear is to angle the worm shaft so that the faces are mostly parallel, a straight on drive will work for the small amounts of power involved.

The higher the ratio, the more tolerant the indexer is to hole place jitter. 40:1 for most indexers, but 90:1 for most rotary tables. If I was to do an indexer (and I probably will later this year), I would do 40:1.
 
I think it's time to bite the bullet and build a worm drive... If there was a better gearing way to do it they would be available that way...I's just the smallest package high reduction gearing design available.

I've cut many a spur gear and angled spur gear...so my first thought was build spur gears with 45 degree angled teeth so then the shafts are at 90 degree. But it's just not as nice as a worm drive for a small footprint high reduction gear set.

Since you're gonna cut a lathe spur gear the big gear should be the easy part for you (and me) . basically an angled spur gear with the center of the tooth dished.....the worm is the part that has been intimidating me.
 
I think it's time to bite the bullet and build a worm drive... If there was a better gearing way to do it they would be available that way...I's just the smallest package high reduction gearing design available.

I've cut many a spur gear and angled spur gear...so my first thought was build spur gears with 45 degree angled teeth so then the shafts are at 90 degree. But it's just not as nice as a worm drive for a small footprint high reduction gear set.

Since you're gonna cut a lathe spur gear the big gear should be the easy part for you (and me) . basically an angled spur gear with the center of the tooth dished.....the worm is the part that has been intimidating me.

I quite agree. This project has to be done inexpensively. And to go buy a worm gear set , it is just too costly. My goal is to make a decent dividing head that won't cost much, that the average hobbyist could build. I try to find ways to demonstrate to hobbyists that they can make quality tooling at a reasonable cost. This is going to be another one of those projects. I have been studying photos of some old dividing heads that were kind of simple and many use a straight tooth gear, I just haven''t figured out how they made the worm fit. ( I need to look at some in person) and some used worm gears. Some of the old heads I have been studying were not 40:1. they vary in the ratio. I think if you design the hole plates to go with the ratio you use, the ratio is not that important. ( at least that is what it seems at the moment) There is an article on Harold Hall's web site that gave me a lot of good information. This head is also not going to be a big honking monster. I want it to fit smaller mills also, and it will tilt to work vertically or horizontally. I have most of my design. The gearing is what is holding me up at the moment.
 
There is an article in HSM about fitting a worm drive to a mini lathe mounted indexer. The worm was to drive a module 1 gear - 20deg. pressure angle and tooth spacing approximately 1/8 inch. The lathe tool was ground to a 40deg angle instead of 60, and the threads cut at 8-TPI. The angle and TPI would have to be changed to match whatever gear you choose. While the best way to transmit power between a worm and a spur gear is to angle the worm shaft so that the faces are mostly parallel, a straight on drive will work for the small amounts of power involved.

The higher the ratio, the more tolerant the indexer is to hole place jitter. 40:1 for most indexers, but 90:1 for most rotary tables. If I was to do an indexer (and I probably will later this year), I would do 40:1.

I have a rotary table that was made ( where else ) in China and I know it is not 40:1. They make a kit consisting of plates and crank and fingers to replace the hand wheel and convert it to a dividing head. Now since they are NOT using a 40:1 ratio, this was what convinced me that as long as you design the hole plates to work with the ratio you have , it doesn't really matter what the ratio is to a point.

I am looking at using 30:1 as it is what is available.
 
Another thought I had is to use a piece of acme screw for the worm and cut a gear like I did for the thread dial I made that rides on the acme lead screw of the lathe. that should work .
 
I have a rotary table that was made ( where else ) in China and I know it is not 40:1. They make a kit consisting of plates and crank and fingers to replace the hand wheel and convert it to a dividing head. Now since they are NOT using a 40:1 ratio, this was what convinced me that as long as you design the hole plates to work with the ratio you have , it doesn't really matter what the ratio is to a point.

I am looking at using 30:1 as it is what is available.

I have one of those Chinese tables, too. It is 36:1. 10deg. per turn of the handle. The bearings are bad, the backlash ridiculous, and the center recess not in the center. I don't use it. I keep it as a monument to my unwise thriftiness.

Looking forward to the project.

Larry
 
The requirements for this dividing head so far are:

1. I will have a spindle that has a 1 1/2-8 thread to match my lathe tooling which also matches my little manual rotary table. This makes tooling interchangeable.
2. The head will tilt 90 degrees so it can be used vertically or horizontally. This is a challenge but I think is do-able with some planning.
3. The spindle will also accept 3C collets. ( 5C are too large to fit in the 1 1/2-8 spindle. however, an ER 40 chuck can be fitted to the front of the spindle.)
4. The plates will also fit on the the spindle for manual indexing and there will be an indexing pin that can be installed . ( I hope). The worm will be removable for this set up.


If there are any ideas for features I have missed , suggestions are welcome.
 
I have one of those Chinese tables, too. It is 36:1. 10deg. per turn of the handle. The bearings are bad, the backlash ridiculous, and the center recess not in the center. I don't use it. I keep it as a monument to my unwise thriftiness.

Looking forward to the project.

Larry


Wow! mine is nice. It had some backlash , but it adjusted out really well. everything else is good on mine. ( it came from CDCO ). the only thing I think was stupid on their part is if you use it vertically it needs a 1/4" shim under it to keep the hand wheel from hitting the table.
 
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