# Threading my mini lathe spindle and using ER-32 collets.



## princerobin (Mar 5, 2012)

Hey guys, 

Have been thinking of threading my mini lathe spindle. My two other lathes (Taig & Logan 10") are threaded and I like being able to switch chucks quickly. I had also thought to change the taper to fit ER-32 collets...

It certainly looks like there's enough meat on the spinlde end for the 40x1.5mm thread. It's an imperial lathe but I think I can get close to a 1.5mm pitch. All threading and boring would be done in the lathe itself so concentricity would be good. 

I'd also have to make some threaded back plates for chucks (standard 3 jaw and 4" 4 jaw). 

What do you guys think. (my question mark key is busted!) 

Regards 

Robin


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## ninefinger (Mar 5, 2012)

I think that you need to consider that the mini-lathe has a reversible spindle and as such a threaded on chuck could be dangerous if run in reverse. A locking mechanism would be needed to prevent it unthreading. 

Mike


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## n4zou (Mar 5, 2012)

I've used lathes with threaded spindles for may years. I cut metric threads with it which requires running it in reverse because the half nuts can not be disengaged from the lead screw until the threads are finished. I've never had any problem with the chuck coming lose. As a matter of fact sometimes I have great difficulty switching chucks because the backing plate threads get very tight on the spindle due to taking heavy cuts. I've had to put a cheater bar on the chuck with the back gears engaged locking the spindle so I could get the chuck loose. Of course one can not take cuts while operating the spindle in reverse. 

As for turning threads on the spindle, that may not be possible. Spindles are hardened after they are machined at the factory so all you may do is burn up tools attempting to cut it and screw up your spindle in the process. The best thing to do is leave it alone.


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## lordedmond (Mar 6, 2012)

look at threaded on chucks from a different slant ( yes my lathe has a threaded nose it has a safety screw lock )

its not running the lathe in reverse they run un slowly for threading its ok , but if the spindle suddenly stops in your case lets say a gear damage locking it up if you are in normal ration at this time the chuck will unscrew , believe me i know


in this case the chuck is rotating anti clockwise 


as in righty tighty lefty loosey

Stuart


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## steamer (Mar 6, 2012)

As Stuart has pointed out, inertia can get you on a threaded spindle....but why thread a non threaded spindle?

Just to swap tooling?  The mini comes with a 3 jaw already. That leaves a faceplate and 4jaw to swap in.  Would the chucks from the other lathes even fit on the mini?

Things to think about....but I can understand wanting to standardize your tooling...


Dave


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## princerobin (Mar 6, 2012)

Thanks for the replys guys,

Like I said before, both my other lathes have threaded spindles. The Logan has a 6" chuck, and it is also reversable. So far no problems with it. 

I'm not sure if the spindle is hardened or not, but I doubt it. I got the idea for threading the spindle here 

http://www.toolsandmods.com/marty-nissen-project-lathe.html

But I think I'd rather set it up to use the ER collets, with no chuck. Quick and easy use of the collets is one of my favorite thing about the Taig, even if the collets aren't great. I wouldn't be swapping chucks from the other lathes, just using the 3 and 4 jaw i have for the mini. 

One concern is threading the chuck back plates. I'd have to do it on the Logan lathe, and the thread I use to approximate 1.5mm pitch wouldn't be the exact same as the one on the mini lathe.

I really never change the chucks on the mini now, it's had the 4 jaw mounted for a few years now.

Regards 
Robin


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## Blogwitch (Mar 6, 2012)

There is no need to thread your spindle, either buy or make one of these and use the original fitting you have on your lathe.

http://www.arceurotrade.co.uk/Catalogue/Collets/ER-Lathe-Collet-Chucks

I am sure that if you have the facilities and know how to thread a spindle and cut the taper for an ER collet, then one of these should be a piece of cake, and you can easily revert back to a normal lathe later if you wish to do so.

Also, by machining the ER taper and screw with it all bolted up, with a nice tight recess in the back to match your chuck mounting, you can't get any more accurate than that.


John


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## princerobin (Mar 7, 2012)

Lots to think about, thanks guys

Robin


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## rake60 (Mar 7, 2012)

I don't know what your budget is for this project, but _*LMS*_ just happens to 
have an ER32 collet chuck for the mini lathes on special this week.

Rick


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