Barrel holging jaws

Russ I believe you are right, I don't do many barrels smaller than .900 at the muzzle. But I am going to put a taper to the jaws per your good suggestion.
Thanks. Chet
 
I think we have some misunderstandings. The argument probably should be.....independent vs universal.

We have 12 engine lathes in our shop, ranging in size from a small Monarch EE tool room Lathe to a 44 foot long LeBlond NR.

Whether a 4 Jaw independent or a 3 or 6 jaw universal stays on a machine is predicateded on what operation the machine will be used for. All of our larger lathes, (30 inch swing and above), don't even have universal chucks. All of our medium and small lathes have both.

Keep in mind, we are a strictly manual machine shop. The type of work in the industry we serve simply does not lend its self to CAM or other types of numerically controlled machines.
 
EASE UP GUYS.. If you are chambering through the headstock and using an outboard spider, if, in the chuck end, you will simply chuck on, at each jaw, about 1/4 of a pre 1982 penny you will have plenty of holding power while the barrel is free to not be distorted by the shape of the chuck jaws.



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JerrySharrett said:
EASE UP GUYS.. If you are chambering through the headstock and using an outboard spider, if, in the chuck end, you will simply chuck on, at each jaw, about 1/4 of a pre 1982 penny you will have plenty of holding power while the barrel is free to not be distorted by the shape of the chuck jaws.,
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I use a piece of 1/4" dia. copper wire wrapped around the barrel for chuck jaws to bite on. Many ways to get the results you want with the equipment that you have.
 
R Stiner said:
Chet

Take a look at the marks on the barrel from your jaws.
You can see one mark bigger than the other. It may be from the barrel being forced to one side of your jaws or not.

Back three of your jaws away from the barrel leave the fourth jaw under your barrel with the barrel resting in the curvature of the jaw lightly push barrel to the side it will want to rise slightly as it moves. that will put your barrel in a bind!

It's called school of hard knock's! "I haven't graduated yet"
I made the same mistake!

Russ
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To me, I would think that the least number of contact points the better. Four is certainly a minimum. Also, I would think that the contact points, or jaws, should be radiused in the front-to-back direction (along the barrel's axis), like the radiused noses of the threaded studs, so that when the spider is adjusted, which will incline the barrel, that the barrel is free to pivot on these radiused contact points. Any "depth" to these contact points will tend to hold the barrel like the flat jaws of a vise and not let it pivot.

A maybe even better "jaw" design might be one where the contact parts are not radiused studs but rather straight "bar" contacts, maybe 1/4" long say, that are radiused front-to-back. This way when the barrel is inclined by adjusting the spider and therefore the barrel, where it is being held by these contacts, should skew off the center axis of the spindle (while centering the throat area) the straight bar contacts will still be in contact with the major O.D. points on the barrel whereas the radiused points of the studs will go off-axis (hard to explain). The three-letter symbol here: lOl depicts how two of the "bar" contacts would look like when viewed on-axis with the barrel. If the barrel, the "O" here, were to slew up or down when adjusted (by the four jaw chuck or the spider) the straight bar contacts would not tend to capture the barrel but allow it to move up of down. The other two bar contacts at the 12 and 6 o'clock positions would do the same in the left-right direction.
 
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