4 jaw independent independent chuck

[EVguru]

Turning irregular shaped pieces of material. Sound like wood turning.

Run them between centres. Since it's plastic, you might even find the fast way to do it is with wood turning tools.

People seem to have forgotten that early metalworking lathes weren't even supplied with chucks!

[oldtiffie]

This is a classic case for a fixture to be made to mount on a plate that in turn is located and bolted to the lathe face-plate.

It will not require a chuck and can be made from scrap. It can be mounted or demounted from the face-plate in a matter of minutes.

All that is required is a bit of careful job analysis and creative and lateral thinking and you are there.

Face-plate work is never mentioned here - but it should be.

It is as much an art as a craft or a science.

It was in common use in workshops in the not so distant past.

It was an essential part of every Apprentice's training.

Face-plates work well on rotary tables as well.

So if the OP has a mill and a big-enough rotary table with (or make) a face-plate - use that instead of the lathe as it will eliminate all the problems associated with unbalanced work on a face-plate on a lathe.

Face-plates used with a rotary table come in very handy on a shaper or slotter. Same on a boring-mill or a vertical lathe etc.

[andy_b]

What I want to be able to do is quickly center a piece that may be square, may be rectangular, and will be variously sized and likely trapezoidal. It might have three sides more or less flat, then the last side rounded, or it could have one concave side and one convex side, with the remaining sides sort of flat, but not necesarily parallel. Being able to center it both ways allows me to turn it round and have it be as large a diameter as possible once all the flats are turned off. If I can't do this quickly, my next best way is to shim it in the three jaw until it's more or less centered. This doesn't hold very well, so I waste time taking light cuts until I've got all the flats removed.

i'm missing something. in your examples above, if three sides are square and flat, and one side is concave or convex, won't you need to adjust the jaw for that fourth side independently? it really sounds to me like a plain old four-jaw with four independent adjustments would work fine.

your idea for the opposed-jaw adjustable four-jaw sounds cool, but it seems like it would only be useful for square or rectangular pieces. those shapes can be set up in a four-jaw in about one minute, and i ain't no machinist.

andy b.

[Timleech]

This is a classic case for a fixture to be made to mount on a plate that in turn is located and bolted to the lathe face-plate.

.

A Keats angle plate, as at

http://www.collegeengineering.co.uk/Castings/558.htm

when mounted on a faceplate is essentially a 2-jaw chuck, but with the advantage/disadvantage of not being self-centring.

Tim

[Carld]

I have never found it that much a problem to center work in a four jaw regardless of the shape.

I have never used the four jaw with a scroll to open the jaws after centering but to me it may still need some centering after opening and closing the jaws with the scroll, especially with irregular stock.

[oldtiffie]

Originally Posted by oldtiffie
This is a classic case for a fixture to be made to mount on a plate that in turn is located and bolted to the lathe face-plate.

A Keats angle plate, as at
http://www.collegeengineering.co.uk/Castings/558.htm

when mounted on a faceplate is essentially a 2-jaw chuck, but with the advantage/disadvantage of not being self-centring.

Tim

Thanks Tim.

Good thinking.

[quasi]

Quit flinching away you guys. The anticipation of learning the uses of four jaw chucks is far worse than the reality. Grow a pair.

ROTFLMAO!!!!!!!

[Peter.]

What I want to be able to do is quickly center a piece that may be square, may be rectangular, and will be variously sized and likely trapezoidal. It might have three sides more or less flat, then the last side rounded, or it could have one concave side and one convex side, with the remaining sides sort of flat, but not necesarily parallel. Being able to center it both ways allows me to turn it round and have it be as large a diameter as possible once all the flats are turned off. If I can't do this quickly, my next best way is to shim it in the three jaw until it's more or less centered. This doesn't hold very well, so I waste time taking light cuts until I've got all the flats removed.

Using the four jaw chuck would be fine if all the pieces were the same size, but that's not the case. My four jaw is a bit of a pain to adjust, and that takes up time as well, thus my desire to have this custom chuck.

It's a tool, and I don't mind making it. It's something that I'd like to have, not an essential. Probably a winter project.

I can see how to make it work using combination left and right hand threaded actuator rods, crossing at the spindle axis. This merely requires the threaded holes in the jaws to be at two different heights. It won't be hard to center these rids either, it's a matter of using some hollow setscrews around the perimeter of the chuck plate. What I will be missing is the thru-hole, but for this application I can't see needing it.

Now for the procedure to make these left/right threaded leadscrews- and thread two of the jaws left hand-

Use your tailstock ram to hold the piece against the chuck face, visually centering the part around the OD of the ram, then wind in the 4 independant jaws.

[Boucher]

EVguru wins the prize for the correct answer. Do it between centers. Don't make it harder than it is.