what size chuck should i run? also, any got chucks 4 $$$?

[steve schaeffer]

hey, just want to pic your guys' nuggets; on my 12" lathe, what size, in your opinion is the ideal three jaw, and ideal 4 jaw size? in regards to the three jaw, i obviously wouldnt want to run a 12" chuck, because i would never be able to open the jaws. just would like to see what you guys are running, or think i should run before i buy. also, if anyone has some chucks for sale, i am intereste, if they are a 2 1/4 threaded back plate type. finally, that is also a point of confusion, as enco offers plain back, and then bison set-tru. i like the bison set-tru, sounds like a good idea. would it be beneficial to buy one back plate then bolt and unbolt when i need to change chucks? or two back plates where i would unscrew and remove and replace with other chuck assembly?
steve.

[lynnl]

I've never set up one of those set-tru chucks on a backplate, but my understanding is that it's something you'd only want to fiddle with just one time and get it exactly right, then leave it alone. As for the 4-jaw, I don't understand where the set-tru issue would enter the picture. Normally with a 4-jaw your intent is to true up the workpiece itself, so the absolute concentricity of the chuck body isn't that critical anyway. (Obviously you'd want it reasonably true.)

The short answer: I'd darn sure get dedicated backplates for each chuck, install them, and then leave them alone.

[JCHannum]

For my 13" Sheldon, I have 6" & 8" Buck Adjust Tru three jaw chucks, Bison 4" three jaw, 6", 8" & 10" four jaw chucks, 10" face plate and catch plate. Also 5C collets and drawbar. Go for it. I use them all.

[SGW]

I'd say "ideal size" depends on what you need to do with it. If you're working with teeny stuff, a monster chuck, while it may be usable, isn't going to be the most convenient. And of course if the work is too big a small chuck can't hold it.

As per JCHannum...get one of everything! :-)
But if forced to choose, I'd probably lean toward a 6" 3-jaw and an 8" 4-jaw.

Oh -- as per lynnl -- don't mess around with changing backplates. Set up each chuck on its own backplate and leave it alone.

[steve schaeffer]

ok.
lynn, sorry about the confusion, i didnt mean buying a set tru 4 jaw. i dont think one exists as per the reasons you mentioned above.
you guys have reaffirmed what i was kind of thinking, each chuck gets its own backplate. as far as getting one of each, boy jc, you are very fortunate to have all that money! i dont suppose you want to just give me one of yours? haha
i am assuming it is feasable to have a larger 4 jaw so im thinking i will probably get an 8 inch 4 jaw, and a 6"(maybe an 8")set tru three jaw. so whats the trick with these back plates? i have to face them off when i install them or what?

[lynnl]

My mistake actually. After I responded I re-read your original and realized that you had said nothing about a 4-JAW set-tru. As I reflect on it I think you'd find swapping backplates about as convenient as having one set of tires to swap around between 2 or 3 cars. It'd get old fast.

[merf23]

I have a southbend 4 jaw chuck which i believe is a 2 1/4 - 8 size, 6" diameter...ill have to check both specs. It came with my 13" SB, but my spindle is 1 7/8 - 8. Id be willing to trade for one that fits mine or sell mine outright.

[yf]

For maximum concenticity the backplates should be machined on the lathe they will be used on.

For a semi finshed backplate that means turning to dia, facing off, turning a spigot or if you have a rare chuck with a spigot on its back, a cavity.
Then pressig the chuck onto the backplate mark the holes for the mounting bolts drill tap etc.

For making one from scratch its more work. First boring and threading for the spindle, then facing off the back etc.

There were some good threads on making backplates not too long ago. Do a search, its working now.

Hope this helps.

[Kerry.S]

8" three jaw and a 10" four jaw that's what we use on out 14"
kerry

[Thrud]

Steve
Bison makes high quality chucks - well worth the money. You can buy them with an integrated thread if you do not want to make one. They cost a little more than just a flat back chuck and a back plate. Also, you can get away with a smaller backplate with 4 jaw independent chucks as they normally have a smaller hub than the chuck diameter. For example, a Bison 6-1/4" 4jaw independent uses a 4" back plate.

[This message has been edited by Thrud (edited 04-05-2003).]

[Oso]

Poisonal opinion is to get a larger 4 jaw, and a smaller 3 jaw.

Probably an 8 inch 4 jaw, and maybe a 5" or so 3 jaw.

I like smaller 3 jaw chucks, they just seem more "in scale" for smaller work. Also, they tend to have jaws that will hold small things, whereas larger ones tend to have larger "work diameter" minimums. Kinda like jacobs chucks....0-1/4, but 3/32 - 3/4..

A set-tru will be your best friend if you get one. Chucks have runout, and with the set-tru you can get right on.

The big advantage of a set-tru over a 4 jaw is that you clamp the work, and adjust the center INDEPENDENTLY. A 4 jaw holds and adjusts with the same screws, which is much less convenient.

You will adjust it from time to time, as even with a new chuck, the runout will vary depending on work diameter and consequent jaw position.

Everyone gets their own backplate, doubtful two would fit the same chuck anyway. A set-tru definitely won't fit anything other than its own, and the long spigot won't fit anything else.

[This message has been edited by Oso (edited 04-05-2003).]

[steve schaeffer]

thanks for all of your info, this sheds some light on the vague things that i dont see everyday. thrud, i like bisons chucks, they are value priced and well made. i have one on my clausing.

merf, email me i am interested.

[This message has been edited by steve schaeffer (edited 04-05-2003).]