Pratt Burnerd chuck

[Mike BrettParticipant @mikebrett89695]

Hi

I have a three jaw chuck , Pratt Burnerd I believe, that came with my Myford ML7 . I made the mistake of over tightening it on the limits of its travel and have broken of the end tooth on the inner edge of jaw no 2. It has the number stamped on all the jaws and the body 95601.I can still use the chuck but the broken tooth is a bit annoying. Would I be right in thinking that the jaws are made to fit one body only . If so is there anything else I could do other than buy a new chuck.

Mike

[Mike BrettParticipant @mikebrett89695]

Broken tooth

[JohnFParticipant @johnf59703]

Mike try Rotogrip I am pretty sure they do spare sets of jaws, the numbers are from the original production, spare jaws will have a different number but that so you don't mix jaws from different sets. When new the body and jaw numbers are usually the same but spare jaws will differ.

John

[Mike BrettParticipant @mikebrett89695]

Thanks for info John, there not cheap but cheaper than a new chuck.

Mike

[Mike BrettParticipant @mikebrett89695]

Thanks for info John, there not cheap but cheaper than a new chuck.

Mike

[John BaronParticipant @johnbaron31275]

Hello Mike,

Why not buy a set of soft jaws for your chuck ! Cromwells sell them I paid £20 for mine. Much cheaper than PB want for a set and far more versatile.

[Brian WoodParticipant @brianwood45127]

Hello Mike,

You can change the order in which the jaws are loaded as an alternative. Try 1 – skip- 3- now 2.

I have a chuck with a broken tooth on Jaw 1, it works perfectly well using the sequence 2-3-1

Regards Brian

[Mike BrettParticipant @mikebrett89695]

Brian

Yes I use the order 1-3 then 2, works fine as long as I remember not to try gripping to large a piece.

John

What do they mean by soft jaws, how soft are they .

Mike

[Pete RimmerParticipant @peterimmer30576]

Mike,

What are the jaw width, slot width and tooth pitch?

[Brian HParticipant @brianh50089]

Mike, soft Jaws are soft enough to machine to, say, fit a specific diameter of a part that you have machined and need to set it up to machine the other side. They can be used inside or outside.

Brian

[Mike BrettParticipant @mikebrett89695]

Brian

Thanks for that.

Pete

Jaw width is 14.16 mm, slot width , ie distance between slots is 8.36 mm, slot height is 4.55 mm. Not sure what you mean by tooth pitch but there are 7 teeth on each jaw.

Mike

[John BaronParticipant @johnbaron31275]

Hello Mike,

I'd forgotten that I had put pictures of my soft jaws and the modifications that I did to make them far more useful.

The commercial soft jaws that I bought from Cromwell are the ones behind the new aluminium ones screwed on to the front of them

The beauty of doing this is that I can just throw them away and screw another set on the front. A very big advantage is no run out ! You put a piece of round bar in the chuck behind to clamp onto and machine the jaws to suit whatever you want to hold in them. You can see in these pictures a step in the original soft jaws where they were machined for a particular job.

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