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Malc-Y
09-18-2006, 08:44 AM
I have just bought a new Pratt-Burnerd 10" 6 jaw Griptru chuck for use on my Colchester Triumph 2000 lathe (£165, is this a bargain or what!!!?) It appears to have been sat around in its box for some years a has very slight surface rust on the back and is complete with both sets of jaws and key. Unfortunately there are no instructions with it and I am not familiar with Griptru chucks, so my question is what is the procedure for adjusting them? I'm sure it is a simple procedure, any help will be appreciated.

Malc. :)

JCHannum
09-18-2006, 09:19 AM
The chuck has four set screws at the rear of the chuck body that bear on a spigot on the backplate. These are used to adjust the chuck as you would a four jaw.

Loosen the socket head screws that hold the chuck to the backplate, these are the six screws on the OD of the face of the chuck.

Chuck up a piece of stock of the desired diameter and indicate it as you would with a four jaw. Using the four set screws, you can dial the part in. It is the opposite of a four jaw as you are moving the chuck, not the part. Once the part is dialed in, tighten the mounting screws.

These chucks are intended for fine tuning for a specific diameter, and may not offer the same repeatability with a different diameter of stock. They typically offer adjustment in the range of +-0.010" - 0.020".

Congratulations, that is a good buy for an excellent chuck.

Timleech
09-18-2006, 12:05 PM
The chuck has four set screws at the rear of the chuck body that bear on a spigot on the backplate. These are used to adjust the chuck as you would a four jaw.

Loosen the socket head screws that hold the chuck to the backplate, these are the six screws on the OD of the face of the chuck.



My griptrus are not adjusted that way. I'll see if I can find the instructions & scan them for you.

Tim

JCHannum
09-18-2006, 12:23 PM
I think Grip Tru refers to the 6 jaw feature, while the adjustable PB chuck feature is called Setrite. The Setrite adjusts in the same manner as a Buck and other similar chucks as described.

BTW, a 2year old catalog price for the 6" 6 jaw Setrite is $1091, plus an additional $200 or so for a backplate.

Timleech
09-18-2006, 01:22 PM
Try

http://web.onetel.com/~duttondock/Pictures/griptru-1.gif

and
http://web.onetel.com/~duttondock/Pictures/griptru-2.gif

Sorry I didn't manage to persuade the butler to iron it first :rolleyes:



I have just bought a new Pratt-Burnerd 10" 6 jaw Griptru chuck for use on my Colchester Triumph 2000 lathe (£165, is this a bargain or what!!!?)



I've been quoted £125 for a set of inside jaws for a 3.25" griptru, so that is a good price.

Tim

JCHannum
09-18-2006, 01:44 PM
Interesting, I have not seen that style before. It appears they have taken the simple and made it complex.

Timleech
09-18-2006, 02:32 PM
Interesting, I have not seen that style before. It appears they have taken the simple and made it complex.

It's certainly not new, I've got three of various vintages, one could easily be 50 years old, same style.

Tim

Forrest Addy
09-18-2006, 03:14 PM
Regardless or exactly how it's set-up, your lastest acquisition is a dandy chuck but fragile. Use it only for second operations involving light cuts. Do not use it for general purpose machining especially for parting off. Breaking a tool or ripping the work out of the jaws is a good way to cause permanent (but not instantly apparent) damage to a three jaw chuck. I refer to damage such as splayed jaws, deformed scroll, or damaged body. For this reason you should preserve your new adjustable three jaw for best and highest useage.

Malc-Y
09-18-2006, 04:20 PM
Regardless or exactly how it's set-up, your lastest acquisition is a dandy chuck but fragile. Use it only for second operations involving light cuts. Do not use it for general purpose machining especially for parting off. Breaking a tool or ripping the work out of the jaws is a good way to cause permanent (but not instantly apparent) damage to a three jaw chuck. I refer to damage such as splayed jaws, deformed scroll, or damaged body. For this reason you should preserve your new adjustable three jaw for best and highest useage.

The chuck is a 6 jaw, not a 3 jaw, so I assume that it will give a lot better grip on the work. The Pratt-Burnerd Griptru chucks are made in 3 or 6 jaw versions in sizes from 5" to 12" diameters and 3 jaw only in 3" and 4" diameters. It certainly doesn't look or feel fragile, it weighs 81 lbs! and that is without a backplate! For heavy work I usually use the 4 jaw independent and true the work with a dti.

Malc.:)

Malc-Y
09-18-2006, 05:05 PM
Try

http://web.onetel.com/~duttondock/Pictures/griptru-1.gif

and
http://web.onetel.com/~duttondock/Pictures/griptru-2.gif

Sorry I didn't manage to persuade the butler to iron it first :rolleyes:



I've been quoted £125 for a set of inside jaws for a 3.25" griptru, so that is a good price.

Tim

Thanks Tim, this is exactly the information I was looking for.

Malc.:)