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Chuck change - what were you taught?

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6001911/07/2012 16:06:06
24 forum posts
4 photos

I've come to a task I have not had to do / seen before; I'm hoping for some help to find out show it should be done.

Previously when I've changed chucks they have been 'screw on' types. The lathe I have at the moment has a short parallel section sticking out from what I'll call a backplate on the head spindle. The chuck is an interference fit on this parallel section, with 3 studs to retain it to the backplate.

Having loosened the nuts on the studs (they won't come off completely until the chuck is part removed) the problem I'm facing is separating the chuck from the spindle as it is a (nice) tight fit.

I have done it, but I'm underwhelmed with the method I used. How should it be done?

Thanks,

Mike

David Littlewood11/07/2012 16:12:03
533 forum posts

Mike

Never come across one of those, but here's one idea. Chuck a piece of MS rod - as large as will pass through the spindle bore, and with a few cm sticking out the back. Tighten jaws, tap back of bar gently until loose.

David

Edited By David Littlewood on 11/07/2012 16:12:37

David Clark 111/07/2012 16:31:35
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3357 forum posts
112 photos
10 articles

Hi There

If possible, I would undo the nuts half a turn or so at a time, perhaps with a spacer behind them so the chuck is forced off evenly.

regards David

Gordon W11/07/2012 16:36:09
2011 forum posts

The chuck should be a close fit but not tight, if it's new this will soon ease off. Don't forget a board to protect the bed. I first put a length of timber in the jaws and wiggled it ( the wood ie.).Now they come off under their own weight except for the seldom used faceplate.

JasonB11/07/2012 17:08:33
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15711 forum posts
1643 photos
1 articles

I use David s method and work round the three nuts to jack the chuck off the spindle spigot.

My 3 jaw was far tighter than the 4 jaw and faceplate , not a bad thing as it helps keep things concentric. To save having to jack the chuck the full 10mm length of the spigot it turned the first 8mm of the recess in the backplate to a shallow taper. This way once the chuck is jacked 2mm it will become looser and the nuts can just be spun off.

I did try the bar and hammer method but the 3 jaw was so tight (almost a press fit) I did not want to damage the bearings.

Ian Hewson11/07/2012 17:35:31
259 forum posts
24 photos

Myfords 254s uses this system (type a3 modified) and they say that the new chucks may be tight, and suggest that a peice of 1inch bar is place in the chuck and struck with a mallet.

Ian

martin perman11/07/2012 17:40:48
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1611 forum posts
67 photos

Mike,

As an apprentice I was always taught to first place a piece of timber on the bed ways so as to not damage the bedways should the chuck slip and drop from your hands. my chuck is held on by bolts and relies on a register and I loosen the bolts and rock the chuck with the chuck key. I have also center popped the chuck and back plate to make sure it goes back in the same place, more for piece of mind. Do not use a hammer as there is always a possibility of Brunelling the bearing tracks of the spindle which would show up in your machining.

Martin P

John Alexander Stewart11/07/2012 18:25:52
749 forum posts
51 photos

With my Emco Compact 8, the "short straight section" is actually tapered. One chuck backplate that I made is a bit tight; a bit of soft wood, a hammer, and a little tap on the back side of the chuck releases it.

I should continue my "scraping" to get it to release on its own, but it's not too bad as is. It's been this way for at least 15 years.

BTW - with the non-screw spindle, one can really easily run the lathe backwards. Some days, I find it a lot faster to just run the spindle backwards, and come into the work from the rear side.

Try it sometime; saves lots of winding back/forth on the cross slide sometimes.

Another JohnS.

Richard Parsons12/07/2012 18:02:44
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645 forum posts
33 photos

I use a ‘Chuck board’. This is a lump of wood which sits on the bed and snugly supports the chuck taking its weight. I then do as David suggests but my spacer is a lump of alloy . I also 'dotted the chuck and backplate so that I always refit them the same way round

6001904/08/2012 11:33:17
24 forum posts
4 photos

Just wanted to say thank you to the many contributors.

For any future readers of this thread, I can report that I have now twice successfully used the method described by David above. Sligthly tedious, particularly on the 3 jaw, but effective. The comments about timber/ 'chuck board' were also good.

Thanks, Mike

David Littlewood04/08/2012 18:10:07
533 forum posts

Just an afterthought - I find a carpenter's bench hook makes a very good bed protector when removing a chuck. If you don't happen to have one, it's cheaper to make your own, but if you do, it saves making one.

David

Ian Welford04/08/2012 20:39:14
277 forum posts

David

what a good idea! Have a few modified for certain saws- I;ll modify one to fit a Boxford fongith !

Thanks Ian

Nobby04/08/2012 23:08:12
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587 forum posts
113 photos

Hi Guys
I'm retired now but still use a chuck board on my S 7 . it fits snugley over over the ways.
I had a close encounter with a chuck once in the M/ C shop a guy slapped his lathe in reverse and the chuck flew off and just missed me as I worked on a milling M/C nearby I know I'm drifting away from thread . like that chuck did !!
Nobby

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