Sherlnie chuck for Taig

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lensman57

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Hi everybody,

Has anyone successfully adapted a Sherline 4 Jaws SC chuck to a Taig micro lathe?
I seem to have a lot of difficulty getting the chuck to center properly on the spindle even though I have taken great care in turning the spacer.

Any help is welcome.
Regards,

A.G
 

dwentz

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I have lots of 3/4-16 stuff that I use on my Taig, but do not have a Sherline Chuck, but have run into this with other things mounted on the Taig early on. There are two things you need to keep in mind with a threaded lathe nose mount. They are the seating face of the chuck to the spindle and the thread length. The seating face is what keeps the chuck square to the headstock. The threads are what center the chuck to the spindle. As you are having problems with the chuck centering correctly then check to make sure that the faces of your spacer are even and that it is a loose fit over the threads so it can move around a bit. The only purpose of the spacer is is allow the chuck to bear against the spindle seating face of the spindle. When you tighten the chuck onto the spindle the angles of the treads act as the centering device and will pull the chuck onto center. There are a few things that can keep all this from happening. The rear face of the chuck is not threaded parallel to the threads. The threads are dirty and are keeping the chuck from self centering. Another thought would be that if your spacer is too tight on the spindle, or if your spacer is threaded onto the spindle then the chuck might not be able to move enough to get on center.

How are you measuring the chuck to see if it is on center? Is it off the same amount all the time?

Dale
 

lensman57

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Hi dale,

Thanks for your reply, I measured the run out using a 5" length of silver steel ( drill rod). The run out is about .05 mm about half way and a lot worse at the extreme length.
The derline spacer is about 5mm thick or just over 3/16" and is not threaded. it slides OK just over the threads, but sits flush on the Taig's register. The chuck is brand new and I know that some people have used this chuck to great accuracy on the Taig. I just don't know how I could improve the machining of the spacer to achieve two truly parallel surfaces given my rudimentary equipment.

Many Thanks,

Ali Ghazizadeh

 

dwentz

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It might be the derlin, flexing when you tighten it down. Try making one out of metal and see what happens, Should be a simple lathe job if you have another chuck, cut a little longer than needed bore and face both sides to length. The length is not critical, a little longer is ok. If you do not have another chuck mount the chuck you have and when you face it off turn it 180 deg in the chuck when you flip it over in the chuck. This should take care of getting most of the error out. Take light cuts to keep the derlin from flexing. Even with the runout the faces will be close to parallel. The bore will be off a bit, but that should not matter, all you care about is the parallel surfaces of the spacer.

Also have you checked the spindle to make sure it is running straight? I do not know what other tooling you have with your Taig, When I first got mine many years ago I had a bad spindle as it would not run true. Taig replaced it when I called them about it.

Dale
 

steamer

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on MOST lathes with threaded spindle noses, the thread is just to hold the chuck on, and is not very close a fit.

The register diameter at the base of the threaded spindle nose is what locates the chuck axially and radially. This needs to be a close ID/OD fit with a good shoulder.

NOW I say most, because I don't own a Taig...but the above is the accepted practice of the past 100+ years or so with lathe builders......

Dave
 

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