Lathe Chuck Jaw Positions

[Franko]

Scrolling lathe chuck jaws are numbered and have to be inserted in a particular order.

Does it matter what slots they go in other than the next slot that the spiral turns to?

I've always stamped a number near the slots on the chuck to correspond to the jaw number, so I can put them back in the same slots every time. Is that really necessary?

 

[eeler1]

Try it, see what happens!! Every chuck I've owned has had the number on the jaw and on the chuck body. You should get a cattywonker axis if you don't insert them in the right order.

 

[JimDawson]

Maybe not, as long as they are put inserted in the proper order. But just as a matter of good practice, I would put them back in the same slot for hopefully the best fit.

I had to hand fit the jaws in my junk import independent 4-jaw, and those jaws will only fit properly in their respective slots.

 

[Franko]

It definitely matters what order you put them in as the thread grooves are offset differently on each one to allow for the travel the preceeding jaw has made when you insert the next one.

I remember in the mid-90s when I got my first (Emco) mini lathe. The first dozen or so times I changed the chuck jaws would take several tries before I (accidentally) got them in the right order. Then, I finally noticed the stamped numbers inside the grooves.

It shouldn't make any difference what slot in the jaw makes, as it is just a slot with a spiraling screw. But, it seems that I read somewhere that they should always be put back in the same slot for consistency.

 

[RJSakowski]

Someone on another post had suggested rotating the jaws in the chuck to see if the runout could be improved. As long as the jaws are kept in the same order, they will close properly. However, I tried mine and found that the original location was the best compromise. If you do try this and find a better orientation, make sure that the chuck body is marked to identify the new positions.

(for the benefit of new lathe owners ) Of course, they have to go in on the correct scroll location. When I remove the jaws, I back the scroll off until #3 is free, remove it until #2 is free, then #1. To reinsert, I back the scroll off 1/4 turn and insert #1, holding firmly against the scroll. I then rotate the key to engage the the #1 jaw and insert #2 and engage it, then #3. Close the jaws to verify the installation; they should all meet simultaneously.

 

[Franko]

I used a small stamp to mark mine.



Another good practice when changing jaws (or removing the chuck) is to place a piece of plywood under the chuck and over the ways to protect them in case a jaw falls out when removing them to keep from chipping or damaging the ways.

 

[chips&more]

The jaws are ground in place on the chuck at the factory. So it stands to reason if you change the order of the jaws in any way, you risk changing the accuracy of the chuck. If the chuck never had numbers/marks stamped on the chuck body then maybe the manufacture didn’t care (I would)…Good Luck, Dave.

 

[Andre]

Yes, on nice chucks the jaws are fitted to the slots. In a perfect world where all the slots and jaws were perfect, it wouldn't matter technically. Just the position of the scroll in relation to the order in which the jaws are inserted.

 

[RJSakowski]

The jaws are ground in place on the chuck at the factory. So it stands to reason if you change the order of the jaws in any way, you risk changing the accuracy of the chuck. If the chuck never had numbers/marks stamped on the chuck body then maybe the manufacture didn’t care (I would)…Good Luck, Dave.

You are talking Chinese factory, right? After seeing some of the things they have done, I wouldn't assume anything was actually done right. My Grizzly 3 jaw did not have any marks on the chuck body to indicate jaw position.

 

[blaser.306]

I also had a KING INDUSTRIAL 10x22 lathe that came with a 3 jaw scroll No markings and no way to make it turn without " excessive runout " I received a replacement chuck that had been checked for true and the jaw locations marked. Not perfect but for lots of simple projects that are a single set up , seem to work good enough.