Fitting Chuck Jaws

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Fitting Chuck Jaws

This topic has 25 replies, 11 voices, and was last updated 29 February 2020 at 17:28 by Chris V.

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27 February 2020 at 16:04 #454496
Chris V
Participant
@chrisv
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
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27 February 2020 at 16:04 #10093
Chris V
Participant
@chrisv
Issue
27 February 2020 at 16:09 #454497
JasonB
Moderator
@jasonb
Generally the jaw numbers should match the slots, only chucks with single reversible jaws need the numbers mixing.
27 February 2020 at 16:12 #454498
Chris V
Participant
@chrisv
Thanks Jason that's good to know. Big mallet then (-;

Cheers

Chris.
27 February 2020 at 16:37 #454502
Brian H
Participant
@brianh50089
Chris, the jaws also need inserting in the order 1, 2, 3.

Brian
27 February 2020 at 16:49 #454504
Chris V
Participant
@chrisv
Thanks Brian!

Chris.
27 February 2020 at 17:05 #454507
David Standing 1
Participant
@davidstanding1
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
27 February 2020 at 17:09 #454508
Chris V
Participant
@chrisv
Thanks very much David, that looks like a really handy tip!

Cheers

Chris.
27 February 2020 at 18:48 #454524
Steviegtr
Participant
@steviegtr
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.
27 February 2020 at 19:23 #454528
Chris V
Participant
@chrisv
Nice one Stevie, …..its not just me then (-:

Chris.
27 February 2020 at 19:55 #454536
Dalboy
Participant
@dalboy
Check that you have not mixed the jaws up and that you have two internal and one external.
27 February 2020 at 21:16 #454547
old mart
Participant
@oldmart
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.
27 February 2020 at 22:25 #454554
Dalboy
Participant
@dalboy
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.
27 February 2020 at 22:27 #454555
Enough!
Participant
@enough
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.
27 February 2020 at 22:43 #454558
Neil Wyatt
Moderator
@neilwyatt
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
28 February 2020 at 11:14 #454615
Tim Stevens
Participant
@timstevens64731
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
28 February 2020 at 11:34 #454618
Howard Lewis
Participant
@howardlewis46836
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
28 February 2020 at 15:47 #454637
Chris V
Participant
@chrisv
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.
28 February 2020 at 16:33 #454639
Howard Lewis
Participant
@howardlewis46836
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
28 February 2020 at 16:55 #454644
Chris V
Participant
@chrisv
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.
28 February 2020 at 16:57 #454645
Enough!
Participant
@enough
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.
28 February 2020 at 17:03 #454647
Dalboy
Participant
@dalboy
Posted by Bandersnatch on 28/02/2020 16:57:48:

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.

As far as I know there are two types of 4 jaw chucks independent and self centreing which is a scroll type

Edited By Derek Lane on 28/02/2020 17:05:09
28 February 2020 at 17:06 #454648
Chris V
Participant
@chrisv
Hi Bandersnatch, sorry no my last post was incorrect, I was talking about my 3 jaw self centring chuck. One jaw fitted easily the other two not so much.

My last post was indeed confused! If you re read it & substitute the 4 for position 2 hopefully you will get what I meant, not that it was important, just recognising that part of my question was a bit daft!

Chris.
28 February 2020 at 17:09 #454649
Enough!
Participant
@enough
Posted by Derek Lane on 28/02/2020 17:03:59:

As far as I know there are two types of 4 jaw chucks independent and self centreing which is a scroll type

Absolutely, Derek and I (quite correctly) stand corrected.
28 February 2020 at 18:11 #454656
Howard Lewis
Participant
@howardlewis46836
Unless you are prepared to mess about with shimming the job against one jaw, you are stuck with whatever eccentricity your 3 jaw delivers; which may vary according to diameter being gripped.

A 4 jaw independent chuck puts you in charge. When you start learning the technique, remember that you only need to adjust by half the error. i.e, if the run out is 0.020 you adjust by 0.010, in the hope of bring things into line ASAP.

When you turn the Backplate do make sure that it is a good fit in the chuck body, and that the face is square to the lathe axis. Skim it to be certain.

Go for it!

Howard
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