A (perhaps) silly question....

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Warren White

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....that I should ask lathe chuck producers.

Why are the jaws for a chuck numbered? I know that you put jaw number 1 on the number 1 position of the chuck, but why? I don't see any difference between the individual jaws, and the parts on the chuck don't seem to be milled for a specific jaw.

One of those imponderable questions that I am SURE that someone on this forum knows the answer to.

(I know that there are many more interesting questions, and perhaps I have too much free time on my hands....)
 
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chartle

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The threading for most jaws on the rear of the jaws requires they be in order so they advance to the center correctly. If out of order, one set will get to the middle before the others.


Sent from my iPad using Penturners.org mobile app

Yes if everyone gets shifted over one position, one jaw will be closer to the middle and each one will be slightly further away from the middle than the one next to it.
 

magpens

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Warren,

Yours is indeed a very good question and not at all silly !

Danny is right ... the 4 chuck jaws are in fact slightly different and it has to be this way, because all four jaws start their travel at the outer edge of the chuck under slightly different initial conditions, but they all have to meet at the center .

There is a thread inside the chuck, which is a single thread, that engages all the jaws at different positions as the chuck key is turned. The single thread I refer to is moved around (turned) by the action of the chuck key. Each jaw, as it is initially grabbed by that thread, faces a slightly different startup scenario, but they all meet at the center as you know.

I have never taken a chuck apart to learn the details, but I certainly have by mistake gotten the numbered jaws out of order and that does not work !
 
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skiprat

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The numbered jaws on a scroll chuck can be in any position in the chuck provided the order of mounting them is #1 first then #2 then 3. etc.
I have a 4 jaw scoll chuck fitted at the moment. When I first got it, I selected the positions in the chuck to give me the least error with my most common stock...12mm dia...I then ground the jaw tips to make them better still.:biggrin:
 

magpens

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Thanks for those comments, Skip !

I presume you cannot insert the jaws into random available spaces even if you stick to the order j1, then j2, then j3, then j4 :biggrin:

You would have to insert them (in that order) just ahead of the leading edge of the scroll thread as it is coming around the round-about !

But you could insert j1 into the slot marked 3, then j2 into the slot marked 4, then j3 into the slot marked 1, and finally j4 into the slot marked 2.

I am not going to make a habit of doing this ... just pushing a point !

Helps to know this in the case your chuck slots are not numbered ... you'd just start with j1 in any slot followed by j2 in the next counterclockwise slot (assuming you have a right-handed scroll thread !)

Now, if I have 2 "identical" chucks, neither with jaws in, can I mix up the two sets of jaws, sort them into two sequences 1, 2, 3, 4 (mixed from the two sets of jaws) and get them into both of the chucks and have the chucks work ???????

(This is not a hypothecial question :biggrin: )
 
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KBs Pensnmore

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There is a thread inside the chuck, which is a single thread, that engages all the jaws at different positions as the chuck key is turned.

On the G3 the thread is a spiral/sometimes called a scroll, hence the name Scroll Chuck.
It pays to dismantle the chucks every so often, to clean out the dust and crud that builds up in them after a while.
Wash them out with a petroleum based product, and re assemble when dry, do not use any oil or grease as this WILL attract dust and crud, probably graphite powder would be best, if you needed to lubricate.
Kryn
 
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