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Indexing Odd Numbers

Robert Arnold

Robert Arnold

Joined
Oct 28, 2008
Messages
67
Likes
190
Location
Bushwood, Maryland
Website
thedoghouseworkshop.com
I am looking for suggestions on how I can index odd numbers on my lathe. I have a Oneway and the built in indexing wheel has 48 divisions so as long as the number of sections I want can be divided into 48 and I get a whole number I am fine. I need to do some items where I have 11 segments so I was wondering how anyone else may have solved this issue. The other concern I have is locking the piece down. With the current set-up you can only secure the headstock at one of the indexing whel positions or one of the preset point for the headstock lock. I need to be able to lock a piece lown pretty securely at a very specific point. If anyone knows of some possible solutions or if there are any accessories available that would help me I would appreciate the information.

Thanks
 
360 / 11 = 32.7272727272727272727

Robert, if 11 is key, you might try making your own. At this website you can
punch in numbers to tell it how many spokes you want.
http://incompetech.com/graphpaper/polar/
I put in 11 for the primary and 0 for the secondary and it seemed to work.
For ideas of use, navigate over to Al Stirts web site and look under student
resources. Not sure if this'll help, but it might give you ideas...
c
 
Now that you have the graph of 11 points you can mount that on the spindle with a pointer attached to the headstock.

Lock the spends at the nearest index point. Unscrew the chuck enough to line up perfectly. Now tighten the sets screws of the chuck insert to lock down the position on the lathe.

If you are going to do 11 segments a lot than make a headboard disc with a hole in the middle for mounting on the lathe spindle. Make a locking pin that is attached to the ways. Something as simple as a wood plate that secures to the ways of the lathe under the spindle. Attach a triangular piece of wood with a hinge to the wood and mount a pin that fits the holes in the disc. If you want the thing to be more solid then two pins engaging the disc would hold thither.
 
If you feel adventurous, add a stepping motor to the spindle of your lathe and control it with a simple off-the-shelf circuit and an old computer. I've got full instructions on my web site http://cornlathe.billooms.com/indexer.html and there are links there to 2 YouTube videos with more details.

The result is that you can set any number of holes for your index wheel. Furthermore, you can choose which to use and which to skip (like use 2 holes, skip 3, etc). Pressing a single key on the keyboard goes to the next programmed hole so you don't lose count.

A number of other people have written me saying they've built the system on several different kinds of lathes. I'll be presenting this approach at the AAW Symposium in San Jose.
 
J. Paul Fennell has made and shown his method of making a dividing head. Uses MDF and a cloth measuring tape. I bet if you Googled it - it would show up. I thin Paul has a short video about making the dividing head. Works with any number you want.
Hugh
 
I am also for rolling your own since it can be configured any way you wish and the cost is hard to beat. Two other free and low cost solutions for software are Google SketchUp 8 and DeltaCAD. I believe that DeltaCAD also has a "try before buy" of 30 days.

The stepper motor sounds like an elegant easily configurable solution once set up, but somewhat expensive for anybody not needing it often. I presume that the stepper incorporates a brake. Even though they have good position holding torque, it is not absolutely rigid. BTW, it is also possible to do the same thing with a true vector control AC induction motor (some lathes advertise vector control or sensorless vector control, but it is necessary to have a position feedback device such as an optical encoder for true vector control). Of course, next on the list is then a leadscrew positioning for a cutter also computer controlled. 😀
 
Indexing with a stepping motor is not really that expensive. Total cost is well under $200. While this is more expensive that a single IronFire index wheel, it's not too bad compared to making/buying a number of custom index wheels. This assumes that you use an old hand-me-down computer (generally free from someone buying a new one).

Admittedly, if you don't do a lot of indexing then this is an over-kill. But if you do open segmented work (or ornamental work) this is a great solution.

The holding torque is surprisingly good. If you use a 50 oz-in motor with a 6.5:1 timing belt ratio (which is what I recommend) that gives you 325 oz-in torque on your spindle. With a 4" diameter work piece, that means about 10 pounds of force is needed on the perimeter of the work to cause a slip. In my experience, the timing belt jumps a notch before I can force the stepping motor to move.

In ornamental turning work, we use something like a small high-speed router (called cutting frames) to cut the work and the stepping motor holds the work still enough for a near-mirror finish on the cut surface.
 
325 oz-in translated into units that I can more easily relate to is 1.7ft-lb. Working distance is usually a lot closer than a foot so multiply that by 3 or 4 and you get a number that isn't too bad. But I am wondering if you have experienced any problems with movement from forces exerted by hand power tools like a drill, router, power carver, or die grinder. Maybe a power carving tool isn't something that would normally be used with an indexing system.
 
I think that with power carvers and die grinders I would definitely want a rigid brake of some kind (or fall back to a solid pin in a traditional index wheel).

I've used a Foredom tool on my work, but I held it firm on a flat surface (so that it wouldn't walk around). With the Foredom tool, I've drilled holes and used end mills up to 1/4" diameter. The only thing that happened once with the 1/4" end mill is that it grabbed on the wood and un-screwed my chuck from the spindle. Using a regular drill probably doesn't generate too much torque, but I would want to have it mounted somehow on a flat surface (again, mainly for accuracy). A trim router with a small bit shouldn't be much different from using a Foredom tool if mounted on a flat surface. But with a big router or a big bit I would feel more comfortable with a more rigid indexing method.
 
Another possible solution is to use a bicycle sprocket. You can get a 33 or 44 tooth sprocket. With an appropriate DIY arbor and latch, you could make a 11 step indexing system
 
Circular Saw Blade

Brand unknown (ID worn off, except "Ripping"), but I have a circular saw blade with 44 teeth (11 x 4); from a garage sale, of course. It's 6 1/2" diameter. It could probably be re-bored to spindle size, and a latching mechanism devised.

Circular saw blades can have weird tooth counts. Some of them can be factored into many combinations/skip patterns. With dual or triple latch arrangements (for diameter and latch-to-latch offset), almost any division is possible.
 
Joe Greiner said:
For extremely odd numbers, consider the method by jwitnberg at message #5 here:
http://www.aawforum.org/vbforum/showthread.php?t=1637

I see no limit to the oddness of the divisions, e.g. 17 or so. And the plywood disk is easier to mount than a thin circular saw blade, which might have trouble with spindle threads. You might need to anneal the bandsaw blade for drilling.
Click to expand...

The old link by Dean Thomas doesn't work. Here is the correct link:
http://www.ironfirellc.com
 
I pulled out my ironfire index wheel and it won't do 11. I did find a word document with photos that I wrote for out club newlsetter a bunch of years back on making your own index wheel. I've made several over the years. I will send the document to whoever sends me an e-mail and requests it. Johnclucas@charter.net.
It's pretty simple. just make a disc that fits your headstock spindle (or you could do the handwheel if your willing to modify the lathe a little. While your turning the disc round make a thin mark about 1/4" inside the outer diameter. Now use dividers to step off however many steps you want. It takes a little trial and error to get this but not very long. Then just drill holes or cut notches in the outside, depending on how you want your index pin to work. Rig up an index pin and your ready to go.
 
For under $20, I now have 180 divisions on mine. I'm sort of thinking about adding another 180 so I'd have a lock at every degree.
 
Are you using the indexing to create spirals then having each degree could be a big advantage.

I use indexing to make equal divisions around a piece.
My index wheel has 48 positions
This gives equal divisions of
2, 3, 4, 6, 8, 12, 16, 24, 48

Your 180 has equal division of
5, 9, 15, 18, 20, 30, 36, 45, 60, 90, 180 That my 48 does not have but the 180 doesn't have
divisions of 16, 24, 48
Equal divisions of 5,9, 36 can be quite useful

going from 180 to 360 adds equal divisions of
8, 24, 40, 72, 120, 360.
 
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Joe Greiner said:
And another one

For extremely odd numbers, consider the method by jwitnberg at message #5 here:
http://www.aawforum.org/vbforum/showthread.php?t=1637

I see no limit to the oddness of the divisions, e.g. 17 or so. And the plywood disk is easier to mount than a thin circular saw blade, which might have trouble with spindle threads. You might need to anneal the bandsaw blade for drilling.
Click to expand...

Due to directory structure changes when we went from the vBulletin forum software to XenForo last year, the old links are no longer valid. I thought that somebody might possibly be interested in reading the information in the link. Fortunately, Joe had enough clues for me to exhume the thread, so here is the post that Joe was referencing: http://www.aawforum.org/community/index.php?threads/indexing-wheel.1637/#post-11800.
 
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