Author Topic: How does one work with spur gear or timing pulley stock?  (Read 1170 times)

Offline tvoght

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How does one work with spur gear or timing pulley stock?
« on: October 27, 2016, 11:20:58 PM »
As an example of what I'm referring to here's a link to some timing pulley stock:

https://shop.sdp-si.com/catalog/?cid=p216&filter=a0%3A2%3A.080%22%20(MXL)%3Ba23%3A2%3A0.968&sort=&view=table

Spur gear stock is available in the same format, and my question applies equally to that.

The example I linked consists of 6 inches of timing pulley profile (.948 O.D.) ending in a straight shank .5 inch diameter by .75 inches long.

Are there generally accepted or preferred methods of working with this stock? I imagine the shank in a .5 inch collet in the lathe, but that leaves a full 6 inches of stock extended, and with machining of custom hub configurations etc, taking place at the unsupported end, I wonder about runout and deflection.
It seems cutoff operations would also take place near the unsupported end. Of course, the problems I imagine would be alleviated as the stock is used up and machining took place closer to the shank.

--Tim

Offline steamer

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Re: How does one work with spur gear or timing pulley stock?
« Reply #1 on: October 27, 2016, 11:36:29 PM »
make a collet for the OD of the stock.    That's a ring bored to the exact OD of the pulley/pinion stock, and a concentric OD about .125 larger in diameter.

Cut the ring at one point, and file off the burrs

Now slide this ring over the stock, and grab it in either a collet, or a 4 jaw chuck, or a really good 3 jaw chuck

Now you can turn or bore or part to your hearts content up close to the chuck.

Dave
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Offline gbritnell

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Re: How does one work with spur gear or timing pulley stock?
« Reply #2 on: October 28, 2016, 01:28:33 AM »
What Dave said but here's what I do when using my 3 jaw chuck. I chuck up a piece of stock long enough to support the stock. In your case .75 long should be plenty. I usually allow about .125 wall after boring. Now put a register scratch on the stock that lines up with the center of your number 1 jaw. Bore it to size, remove and cut open with a bandsaw. The cut will be 30 degrees away from your mark. Deburr. Now when you put the stock back in the chuck it should run dead true, well I guess on how good your chuck is. Generally a chuck will repeat for a given diameter so by removing the bushing and putting it back in the same spot it should be pretty accurate. I have a whole box full of split bushings for just those occasions. Make sure you scratch the size of the bore on the bushing for future reference.
You can even reused the bushing for a larger size in the future. Just shim the saw cut, clamp in the same place in the 3 jaw chuck, rebore, remove shims, chuck your material and turn it.
gbritnell
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Offline 10KPete

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Re: How does one work with spur gear or timing pulley stock?
« Reply #3 on: October 28, 2016, 07:22:15 AM »
Interesting, George! I've done that same thing for years, just never thought much about it. It just works...

Pete
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Offline Jasonb

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Re: How does one work with spur gear or timing pulley stock?
« Reply #4 on: October 28, 2016, 07:33:25 AM »
Soft jaws will also do the job nicely

Offline tvoght

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Re: How does one work with spur gear or timing pulley stock?
« Reply #5 on: October 28, 2016, 01:53:09 PM »
Thanks for the suggestions and comments.

I was stuck in the rut of thinking I should be somehow using the straight shank. Dave and George's method is clearly the right approach for my purposes.

For the .948" O.D. pulley I showed in the link, I think I would make the split bushing to fit in a 1-1/8 5C collet. That would work well for me.

Thanks again,

--Tim