Home-made 3AT collet drawbar/closer (need help)

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dampfloko
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Joined: Sat May 09, 2009 12:56 pm
Location: Spartanburg, S.C.

Home-made 3AT collet drawbar/closer (need help)

Post by dampfloko »

I'm looking for help in making a collet closer (drawbar) for an older Atlas/Craftsman lathe. The very decent lathe plus box of 3AT collets were received from a late hobby-machining buddy... but included no means of closing the collet on the workpiece. If the charts I've read are correct, I need to tap 0.637 - 0.640" diameter, 26 threads/inch. I haven't found a correct tap, but (possibly) someone with internal-threading skills should find it fairly easy, given the steel tubing I bought for the purpose. As you may have guessed, gears and parts for the feed shaft are still packed. I expect to pay or otherwise compensate for any help. THANKS! Glenn in South Carolina
SteveM
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Re: Home-made 3AT collet drawbar/closer (need help)

Post by SteveM »

You can pick up pre-threaded drawtubes on ebay for not a lot.

http://www.ebay.com/itm/BRAND-NEW-18-LO ... xyMxpRt0BB

Steve
dampfloko
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Re: Home-made 3AT collet drawbar/closer (need help)

Post by dampfloko »

Thanks, Steve... I'm afraid the link didn't work for me; and a search for 'pre-threaded drawtubes' didn't seem specific enough. Can you copy+paste the 12-digit eBay item number [for example something like 292030586633 ] from a drawtube listing you might be watching? Much apprec!
John Evans
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Re: Home-made 3AT collet drawbar/closer (need help)

Post by John Evans »

Opened Ok for me # is 292048497275
www.chaski.com
SteveM
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Re: Home-made 3AT collet drawbar/closer (need help)

Post by SteveM »

Search on:

3-AT STEEL DRAWBAR

Steve
dampfloko
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Re: Home-made 3AT collet drawbar/closer (need help)

Post by dampfloko »

To John and Steve -- Your suggestion worked like a champ. Many thanks! As you may know, the thread is unusual, not 24 or 28, but 26 threads per inch... helpful to find the difficult part of the job, threading the drawbar, already taken care of. Glenn
spro
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Re: Home-made 3AT collet drawbar/closer (need help)

Post by spro »

Hesitate to speak of failure but it happened. I assume that your nose adapter is perfectly fit and collet runs true. The register at the back of the tube can be a problem. I don't know what Atlas did there but not all spindles are finished/ground at the end for accurate setting. I had to make a spider to fit the OD and locate the rear of the tube. Even that was not as accurate as I wanted. If it comes that you have a problem there, you are not alone.
I turned my tube to fit 5C and pass through the spindle. It was trying to find any tube which near that diameter. The one that I internal threaded was steel and while I had turned the surface, it may have bowed. Different lathe but IF you get a tube which is already threaded straight, you are ahead of this. All except the left register.
SteveM
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Re: Home-made 3AT collet drawbar/closer (need help)

Post by SteveM »

On the Atlas, the back of the spindle is a machined surface that runs true. The drawbar has a removable collar on it that has a taper to force the tube to center in the bore.

Some drawbars center by having a surface on the handwheel end that is larger than the rest of the tube and is a close fit to the internal diameter of the spindle.

Steve
toddalin
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Re: Home-made 3AT collet drawbar/closer (need help)

Post by toddalin »

SteveM wrote:On the Atlas, the back of the spindle is a machined surface that runs true. The drawbar has a removable collar on it that has a taper to force the tube to center in the bore.

Some drawbars center by having a surface on the handwheel end that is larger than the rest of the tube and is a close fit to the internal diameter of the spindle.

Steve
My ShopTask drawbar for 5C collets has a collar (non-removable) with a step, rather than a taper. When I had the spindle changed, the drawbar no longer centered as well as I would like, and I made a brass bushing to go inside the end of the spindle to engage the step that better centers the bar.
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