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Fitting Chuck Jaws

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Chris V27/02/2020 16:04:22
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158 forum posts
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With my lathe came a 5" 3 jaw chuck, with both sets of numbered jaws, inside & outside.

Clearly it hadn't seen one set of jaws for some time as I had to gently persuade two of the jaws that were fitted out with a wooden mallet due to rust.

I now wish to fit the other set of jaws.

Question is do I fit No1 jaw in chuck marked No1 & so on?

I ask as two went in ok-ish but the other is putting up a struggle, obviously I don't want to force it and damage something.

I have a VERY vague memory from metalwork at school that two of the jaws have to be swapped over?

Maybe I'm completely miss remembering but would appreciate knowing for sure?

Thanks

Chris

JasonB27/02/2020 16:09:26
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Generally the jaw numbers should match the slots, only chucks with single reversible jaws need the numbers mixing.

Chris V27/02/2020 16:12:11
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158 forum posts
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Thanks Jason that's good to know. Big mallet then (-;

Cheers

Chris.

Brian H27/02/2020 16:37:39
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1475 forum posts
102 photos

Chris, the jaws also need inserting in the order 1, 2, 3.

Brian

Chris V27/02/2020 16:49:10
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158 forum posts
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Thanks Brian!

Chris.

David Standing 127/02/2020 17:05:36
1288 forum posts
48 photos

To insert jaws of a self centring chuck, this is an easy way.

All jaws should be removed.

Go to empty jaw slot 1. Turn the key until you see the start of the scroll thread cross the slot.

Back off slightly, push jaw 1 in, lightly hold it in, turn the key and engage the scroll thread in jaw 1. As soon as it engages, stop, go to empty slot 2.

Repeat jaw 1 instructions for jaw 2 and then 3.

 

 

Edited By David Standing 1 on 27/02/2020 17:06:10

Chris V27/02/2020 17:09:57
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158 forum posts
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Thanks very much David, that looks like a really handy tip!

Cheers

Chris.

Steviegtr27/02/2020 18:48:10
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827 forum posts
187 photos

Or do what I did & being new to this technology was trying to fit the jaws the wrong way around from the radiused threads. Wondered why it was tight. Live & learn.

Steve.

Chris V27/02/2020 19:23:24
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158 forum posts
20 photos

Nice one Stevie, .....its not just me then (-:

Chris.

Derek Lane27/02/2020 19:55:49
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307 forum posts
70 photos

Check that you have not mixed the jaws up and that you have two internal and one external.

old mart27/02/2020 21:16:26
1252 forum posts
116 photos

I have marked the outside of some of the chucks with the 1-2-3 numbers and the ends of the matching jaws with a vibro etcher for easier jaw changing. The Toolmex four jaw independent is numbered by the manufacturer, but the cheap and not so good Chinese four jaw was numbered by me after juggling the jaws around to get the best fits.

Derek Lane27/02/2020 22:25:04
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307 forum posts
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if you have a set of jaws not numbered looking at the thread you will see that the first tooth on each jaw will be in from the centre slightly from the previous one. See ringed tooth on this set of woodturning chuck jaws.

dscf1483 (1024x330)1.jpg

Bandersnatch27/02/2020 22:27:40
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1489 forum posts
42 photos
Posted by David Standing 1 on 27/02/2020 17:05:36:

To insert jaws of a self centring chuck, this is an easy way.
All jaws should be removed.

Go to empty jaw slot 1. Turn the key until you see the start of the scroll thread cross the slot.

Back off slightly, push jaw 1 in, lightly hold it in, turn the key and engage the scroll thread in jaw 1. As soon as it engages, stop, go to empty slot 2.

Repeat jaw 1 instructions for jaw 2 and then 3.

I use essentially the same technique but rather than watch for the start of the thread each time, I insert the jaw, lightly press it down with a thumb then turn the scroll backwards. When the jaw "jumps" it's at the start of the scroll and I turn the scroll forward to capture it. Repeat for next jaw etc.

Sounds a lot more complicated when written than when doing.

Neil Wyatt27/02/2020 22:43:20
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17391 forum posts
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The problem is, of course, that some chucks are numbered 1,2,3 clockwise and some anti-clockwise...

Quickest soliution

Enter each jaw into a slot (don't worry which ones), reverse the scroll until all three jaws have 'clicked' at least once and appear to be level. Now tighten them up, if one jaw is clearly way out, loosen again applying inward pressure to this jaw until it clicks over the end of the scroll thread and moves in to align with the others.

If it becomes apparent they still won't quite meet in the middle, undo and swap over two of the jaws.

Ideal world.

Ideally, know which slot is for which jaw, so if you have a new chuck, consider marking each slot to match the jaws as supplied by punching numbers on the body.

Best Guess

If you have already removed the jaws, slot 1 is usually the one opposite the logo and if they don't quite meet in the middle swap 2 and 3 to reverse the order and keep jaw 1 in slot 1.

Neil

Tim Stevens28/02/2020 11:14:44
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1143 forum posts

If you are dealing with rusty parts it would be an advantage to dismantle the chuck and give it a thorough clean. In normal chucks the front and back are held together by bolts - usually hex-socket headed - and there is nothing complex about the mechanism. Mark front and back before taking them apart so it all goes back exactly as it was. Once apart the mysteries of which jaw goes where will be obvious - but the main object is to allow for a thorough clean out. Not just rust but odd bits of swarf and crud. A good soak in paraffin (kerosene) will help, followed perhaps by a blast with a pressure washer and ten minutes on a warm stove to dry it all out. Then use (eg) graphite grease in the sliding surfaces as you reassemble, and fit the jaws in the order which you should now understand and perhaps, remember.

Hope this helps.

And PS - the time you need to swap jaws endways is with an independent chuck - where each jaw slides on its own and not as a set. Jaws for this type of chuck can be turned endways to change 'inside' jaws to 'outside' - but you can't do this with self centreing chucks. Exactly why will be clear when you have the bits in your hand.

Cheers, Tim

Howard Lewis28/02/2020 11:34:04
2927 forum posts
2 photos

It may be that the slots, and / or the jaws are dirty or burred.

Having cleaned everything, rotate the three jaw chuck until No 1 slot is easily visible. use the chuck key to rotate the scroll until the start of the scroll just becomes visible

Enter No 1 jaw, and rotate scroll to engage the jaw.

Continue rotating the scroll to repeat for Jaw 2 and then for Jaw 3.

When fully rotated, the scroll should bring all three jaws to the centre. If this does not happen, either you have engaged one of the jaws in the scroll at the wrong time, or one of the jaws may have the first "tooth" broken off.

This is not a complete disaster. If you ensure that the damaged jaw engages with the scroll at the second rotation of the scroll, all three Jaws should arrive at the centre at the same time.

But do not expect absolute concentricity from a three jaw chuck. A good one will hold work to slightly better than 0.005" (0.127 mm ) T I R. A badly worn one could five times worse! You just need to be aware and make allowances for this.

Howard

Chris V28/02/2020 15:47:08
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158 forum posts
20 photos

Thank you all, I'm almost glad I had the problem now, Ive picked up so many useful tips.

BTW it did occur to me after I had made my request that if the manufacturer have gone to the effort of supplying two sets of jaws and had bothered to number them they why would he have numbered say no 3 jaw if its correct position was slot 4! Doh!

Anyway I got the jaws in today, seems to have been localised rust.

Thank you all again,

Cheers

Chris.

Howard Lewis28/02/2020 16:33:33
2927 forum posts
2 photos

Jaw position is less vital with a 4 jaw, since YOU determine the concentricity by the way that you adjust the jaws

A 3 jaw with he jaws incorrectly sited will never meet at the centre, so NO hope of ever holding anything even vaguely concentric

With a 4 jaw if you wish, you can set work concentric to less than half a thou (12 microns for the metricated ) or as eccentric as you wish.

All good experience!

Howard

Chris V28/02/2020 16:55:06
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158 forum posts
20 photos

Thanks Howard, yes setting one up properly is something Ive yet to tackle. With not as much time as I'd like it seems the way forward is to learn these new (to me) ways of working as and when I need them. Not ideal but needs must!

Chris.

Bandersnatch28/02/2020 16:57:48
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1489 forum posts
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Posted by Chris V on 28/02/2020 15:47:08:

BTW it did occur to me after I had made my request that if the manufacturer have gone to the effort of supplying two sets of jaws and had bothered to number them they why would he have numbered say no 3 jaw if its correct position was slot 4! Doh!

Now I'm confused. This suggests you're talking about a 4 jaw chuck (in which case it wouldn't have a scroll anyway). The original post said 3-jaw.

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