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Frank Downey
08-01-2006, 09:15 AM
I Have An Old Chard Lathe With A 14" 4-jaw Chuck.i'm Wanting To Use A 3 Jaw Chuck That I'm Going To Chuck Onto The 4 Jaw.what Is The Best Chuck For My Setup Or What Is The Best Set Up.sometimes I Have To Swap Between Then Both And I Don't Want Alot Of Set Up Time Changing The Chucks.?

japcas
08-01-2006, 10:20 AM
Sounds like a standard plain back chuck will do the trick for you. You probably should buy one in the 10 to 12 inch range max. so the chuck jaws on your four jaw are not extended past the body of the chuck for maximum chucking strength. Good luck.

Frank Downey
08-01-2006, 11:36 AM
Thank You Very Much For The Information On The Chuck.i Was Looking At Them In The J&l Industrial Supply Catalog And The 10" Chucks Are Pretty High,but The 8" Looks Like What I'm After.the Hole Opening Is Plenty And The O.d. Looks Like It Will Work For Me.

BobWarfield
08-01-2006, 12:38 PM
Wow, an Adjust-Tru 3-Jaw chuck. You usually have to pay more for that. Very nice!

Best,

BW

thistle
08-01-2006, 01:16 PM
chucking a 3 jaw in a 4 jaw is a good way to set up for a spectacular wreck.

miker
08-01-2006, 06:11 PM
Thistle, I have seen reference to using a 3 jaw in a 4 jaw in some books. I think it was to keep some type of eccentric set up for multiple parts.
Your comment about this being dangerous has come up on the BB's before also. May have been by you.
Is there a time and place for this type of set up or is it just too dicey to take the chance?
It is the type of thing I might have been tempted to try, not having the experience of others.

Rgds

japcas
08-01-2006, 06:25 PM
This type of setup is no riskier than any of the other stuff done in a machine shop if done properly. This horse has been beat to death before but given the right conditions anything can be pulled out of a chuck. Whether it is a three jaw or four jaw doesn't really matter. The four jaw chuck holding a three jaw chuck doesn't know the difference between the three jaw and another piece of stock. Do you want to hog a lot on a piece held in a three jaw that is chucked in a four jaw, probably not. But there is some instances where it is really handy. Especially if you have a really heavy four jaw chuck and don't have a good way of changing it out for a three jaw. A lot of bigger four jaw chucks will only go down to an inch or so in diameter. In this case, chucking up a smaller chuck saves the day. A little common sense goes a long way. Just remember to be careful and have fun.

JCHannum
08-01-2006, 06:51 PM
This post describes a crash from chucking a chuck in a chuck; http://www.homeshopmachinist.net/bbs/showthread.php?t=14823

The problem was possibly caused by not using a backplate on the smaller chuck. The cast iron body was not designed to handle these stresses and failed. Luckily Christian was not injured.

If contemplating a similar setup, the smaller chuck should be mounted to a proper backplate with a stub spindle. Chucking the spindle in the larger chuck will not impose undue stresses on the smaller chuck.

Some of the other warnings in the thread are valid as well, particularly when it comes to the reduction in the holding power of the larger four jaw at higher RPMS. It is a good idea to take a close look at all the posibilities for disaster before experiencing them first hand.

thistle
08-01-2006, 08:00 PM
There is now way I will piggy back a 3 jaw like that on my big lathe.

It might be an expediant to really get you out a hole in an extraordinary situation, but as an everyday practice -noop

chucks got a spindle nose mount for a reason,change the chuck when you have to how long does that take?

Scishopguy
08-04-2006, 04:20 PM
Thistle, I have seen reference to using a 3 jaw in a 4 jaw in some books. I think it was to keep some type of eccentric set up for multiple parts.
Your comment about this being dangerous has come up on the BB's before also. May have been by you.
Is there a time and place for this type of set up or is it just too dicey to take the chance?
It is the type of thing I might have been tempted to try, not having the experience of others.

Rgds

They make a six jaw chuck that is like having a 4 jaw (for centering accuracy) and a 3 jaw (for rapid replacement of parts). The individual jaws have an adjustment screw and there is a socket that opens all jaws at one time. If you have a lot of parts to make from irregular stock it works quite well. I think the one we had was a Buck.

Jim (KB4IVH)

miker
08-04-2006, 07:34 PM
http://img.photobucket.com/albums/v448/mikerr/Faceplate.jpg

Is anyone familiar with the above device? I have never used the faceplate but having positionable, adjustable jaws looks interesting. This picture/description is in a 1974 college text book. I have never seen this device mentioned on any of the BB's.

Rgds

JCHannum
08-04-2006, 08:50 PM
The faceplate with separate jaws is quite common on larger lathes, around 20 & up is where they will come into use rather than an adjustable chuck.