Trying to sort another 3 Jaw Chuck

[AdrianH]

This is another Pratt chuck, came from the dividing unit going to pdg.

I decided that it would possibly be of use to me if I could clean the thing up.

It is 6 inch diameter and only has internal jaws, but it is a handy size for my own lathe as very similar to what I have, so the idea down the line is to make a backplate and use on the lathe when I have some rough jobs to do such as intermittent cuts, or where I run a risk of damage.

I forgot to take any pics of the strip down and clean out of all the old grease and shavings in there. It is a well battered unit with what looks like hammer marks in the side and face, even two small drill holes in the top surface.

After clean it all moved freely and reasonably smooth, but I did not like all the hammer marks as mentioned.

So with a bar in my lathe chuck and this one also on the same bar I took a 5 or 6 thou cut on the lathe of the outside to clean it up.




Even with the trim on the side there are still some marks left and as you can see the front face has also has some heavy marks.

But it is usable, the internal register on the back of the chuck is still OK. It can go back on a shelf after a squirt over with WD40.

Adrian

 

[AdrianH]

Yes mounting would be an issue until I make the backplate, my 3 jaw on the lathe is about 6.5 inches so I would not like to try with external jaws to hold it.

It will be done at some point.

Adrian

 

[roofman]

Yes mounting would be an issue until I make the backplate, my 3 jaw on the lathe is about 6.5 inches so I would not like to try with external jaws to hold it.

It will be done at some point.

Adrian

dont you have a 4 jaw you can hold it internaly from the register side

 

[AdrianH]

Mmmmmmmm, I could do that with the three jaw on the inside register, think it may be deep enough. That I will look into. Good idea.

Adrian

 

[AdrianH]

OK so could not do the internal register only about 5mm deep. So did it externally, a bit tight on its limits but light cut.
Tapes on the scrolls and a vacuum nozzle near the tip to collect the cast.

Again only about 5 thou cut, I lost the Pratt name and serial number but not the numbers to indicate which jaw goes were. Still some deeper marks but it will do.


Now on the shelf until I make a backplate and need it.

Adrian

 

[slim_boy_fat]

Now on the shelf until I make a backplate and need it.

With a spray of WD-40?

 

[AdrianH]

With a spray of WD-40?

Unfortunately not, can never find it when I want to.

Adrian

 

[rory1]

What you have done makes it much shiney'er but makes the chuck no more usable or accurate than when it was found.

 

[AdrianH]

What you have done makes it much shiney'er but makes the chuck no more usable or accurate than when it was found.

I assume you have not read the beginning of the post to see what the intentions of using this chuck are for?

The scrolls and bevels are quite good on the chuck but the casing had been abused with hammer marks on the sides and top, I guess this could be the norm in some industrial places.
But no I have done nothing to make the unit more accurate apart from clean out the crap. The register on the back is untouched so when mounted the accuracy would be the same as before, and that I will not know until it is on a back plate and I have a bar in the jaws. But it would still be my chuck of choice if doing what I would call damaging work on the lathe.

The light cuts have been to simply reduce the hammer marks on sides and top. It looks a bit better.

Adrian

 

[Screwdriver]

Jaws don't have to go back into the 123 slots by number, just have to be in the right order. Can be useful sometimes to shift jaws around to find the most accurate position.

 

[AdrianH]

I had always assumed that the numbers were there because that combination provided the best accuracy, but I guess that over time things can and do shift depending on wear.

Adrian

 

[Screwdriver]

Yes that's my understanding too

 

[Wedg1e]

For a backplate, assuming you weren't planning to turn one up from scratch, you could try locating a spare catchplate as used for turning between centres: they can usually be had for buttons compared to a proper backplate. My Boxford VSL has the L00 spindle fitting and backplates are £100 a pop, I snapped up an L00 catchplate for £4!
Clean up, fit to spindle, skim the face, turn a register, drill three holes, Roberto is your Italian half-brother's gay uncle

 

[AdrianH]

It is a strange spindle end on the Herbert, in fact it is like the back of the chuck it self, it is a disk with a register and 3 locating holes, so in effect the backplate to the chuck is a piece with a male? register on both faces, one for the spindle and one for the chuck.

as lock would have it I have a spare, just awaiting to get machined for the chuck.
Not a clear picture, as it does not show the spindle end but may give an idea, a nicked picture from the web.



Adrian