# Procedure For L1 Chuck Change? Or Worn Out Chuck?



## AlxJ64 (Jan 3, 2017)

So I've been working on a 1963 Colchester Triumph with an L1 tapered spindle. It came with two Pratt chucks. A 9"-10"ish 3 jaw and a larger 12" 4 Jaw. I haven't mounted the 4 jaw yet but I have had the 3 jaw on and off during the moving of the machine. I remounted the chuck and noticed it had some notable runout. So I thought maybe I hadn't installed the chuck correctly. I removed it with the spanner, and then cleaned everything very well to make sure there were no chips or anything in the way and remounted it and it appeared to have even worse run-out. Did it one more time and the run-out seemed less. I did notice that the jaws were a bit mangled on the chuck and that one of them is quite sloppy in the grooves of the scroll. When eye balling the back of the chuck it appears the step down groove has a bit of a wobble to it. The OD of the truck runs true within .003" on an indicator. Is there a process that is advised for installing the chucks? Draw it up and tap around? Or is it possible that this chuck is just old and abused? I've found a few L1 blank backing plates and some cheap chinese 10" and 8" chucks... don't know if I want to go that route and spend the money on a new chuck when I'm just doing something wrong here.


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## 4GSR (Jan 3, 2017)

Chucks do wear out, or wear to the point where they are not accurate anymore.  And yeah, it sound like your chuck has some amount of wear or damage to the chuck.  I would suggest taking the chuck apart, give it a good cleaning and put a dab of moly disulfide grease on the scroll and gear and re-assembly.  Check runout again.  If the runout is the same, it's time to get a new chuck.  I wouldn't rule out the Chinese chucks.  I have a small 6" 3 jaw I bought fifteen years ago.  I don't use it a lot but when I do it runs dead nuts true.


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## Kiwi (Jan 5, 2017)

Had similar issue with my LO  Colchester Master to clean up I removed the Key and gave the spindle a rub with 250 grit wet and dry and the internal of the chuck boss the same with the 4 jaw, face plate etc then a light smear of bearing blue to check the fit found a high spot on the three jaw I then checked the spindle again for corresponding marks nothing but key had been knocked around a bit which is not unusual so I suspect the chuck may have been dropped onto the key whilst in the on off process so I just gave that area a scrape and a rub with a small stone the outside now runs as true enough but i still need a new chuck I think tend to use the four jaw now


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## AlxJ64 (Jan 6, 2017)

Kiwi said:


> ... now runs as true enough but i still need a new chuck I think tend to use the four jaw now



Yea, I think this is where I am on this one. Problem is also finding a backing plate. I emailed two different places and they never got back to me about it. I also don't like the concept of the import junk on this machine but I also can't afford the nice stuff either. Gotta pay to play.


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