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The Sequel - Oh Blimey I bought a CNC Lathe (Beaver TC 20)

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awemawson:
So next thing is to dismantle the chuck body and try and find out if I re-assembled it previously with the wrong orientation.

The body is in two halves held together with nine cap head screws. Gingerly undoing them the two parts start to separate by the pressure of the internal springs so I carefully marked the current orientation in case it had to either go back as was or rotated depending on what I find.

Well happily (I suppose!) there are three tapped hole to force the two halves apart if it gets stuck, and I could distinctly see the ghost of the holes in the flange that the screws would bear on, and they are orientated as they should be. So no, I didn't cock up the orientation.

Further proof was shown by a tiny locator hole for a pin in both halves with an equally tiny O ring to retain the pin, however the pin was missing !

So I carefully cleaned up the mating surfaces, removed a minor amount of debris and put it back together  exactly as it was, obviously as assembled in the factory, as I thought there was little point in ringing the changes having found the pin thingy.

All back together, and refitted - needless to say the run out is still there but this is to be expected





So next the big leap: Re-couple the hydraulic lines that I had had to blank off at the far end of the spindle, and see if the chuck actually works or whether it spews hydraulic oil everywhere  :bugeye:




Hoo-blooming-ray it actually works. OK there is a run out issue, but perhaps my expectations of a thirty year old heavily used chuck are too high  :scratch:

carlquib:
I'm sure you will have it sorted in no time and the 30 year old chuck will be performing like new.

Sent from my SM-N976U using Tapatalk

awemawson:
Well never take anything for granted.

Just 'cos I could, I swapped the 10 mm collet for a 25 mm collet, and guess what - run out reduced to 20 microns  :clap:

I reckon someone has whacked the 10 mm one that I was using, though it looks OK'ish

AdeV:
 :headbang: :headbang: :headbang:

Nice work Andrew!

It's hard to say from the video, but is that piece in the last one a bit of raw bar stock? How about turning an oversized piece to fit the collet (possibly on another lathe, unless the collets are easy to swap), turn the oversized end true, then flip it end-for-end & see what the runout is then? I'm just wondering if your raw bar (if that's what it is) is not actually perfectly round.

awemawson:
Yes Ade you are right (as usual) it IS raw bar, but a pretty good finish. The collets are the '1st Operation Serrated' type, and when I closely examined the 10 mm one there were bits stuck in the serrations that won't help.

When I get a bit of time i'll dismantle them and give them a clean up. They are only held together by an encircling spring clip, with rubber bits between the sections.

 

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