Pratt Burnerd 6 inch 4 jaw independant lathe chuck

[sean logieParticipant @seanlogie69385]

Anyone have/use one of these . I'm looking at one just and was wondering what the quality will be like .

Sean

[sean logieParticipant @seanlogie69385]

[mark smith 20Participant @marksmith20]

Hi Sean, i use one on my south bend and i like it , they are a good make and quality. They are often on ebay . You can buy threaded back plates for boxford which would probably fit yours such as :

**LINK**

Its best to skim the back plate on your lathe anyway even if it comes with a backplate already attached. That way you ensure its got minimal run out . Though not awfully important with an independant four jaw as you`ll dial it in anyway each time you use it.

Mine came with my lathe but looked to be unused as the jaws are still pretty tight and unworn and it had a boxford backplate on which didnt fit properly on my spindle nose.(until just recently when i single pointed the threads to 60 degrees UN.

I just made another chuck key for mine as its far quicker dialing in using two opposing chuck keys.

Edited By mark smith 20 on 12/12/2016 18:46:13

Theres one here in good condition but needs the back plate.Price seems reasonable.

http://www.ebay.co.uk/itm/6ins-Bernerd-4-Jaw-Chuck-/302163473722?hash=item465a58b53a:g:1t8AAOSw6DtYTUZs

Edited By mark smith 20 on 12/12/2016 18:50:43

[Chris Evans 6Participant @chrisevans6]

I have a 200mm Pratt/Burnerd 4 jaw and think very highly of it. I have the same make three jaw chucks in 160mm for the lathe plus 125 and 100 for fixtures etc. All are good.

[sean logieParticipant @seanlogie69385]

I shouldn't need a back plate with this should I ? I know nothing about chucks . I bought a set of thread gauges and measured the spindle threads , the gauges tell me that the threads are 7G 1/8-1/4 .

http://www.ebay.co.uk/itm/302162526825?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

[V8EngParticipant @v8eng]

I have a Myford threaded one for my ML7, still very nice operation even after some 35+ years with more than one user.

Very good bit of kit, well worth getting a tidy example if pre-owned.

[sean logieParticipant @seanlogie69385]

Posted by Chris Evans 6 on 12/12/2016 18:52:34:

I have a 200mm Pratt/Burnerd 4 jaw and think very highly of it. I have the same make three jaw chucks in 160mm for the lathe plus 125 and 100 for fixtures etc. All are good.

I was looking at the 200 mm version ,I'm unsure if it will be to big or not . My lathe 3 jaw measures 6.2 " Lathe has a 12" swing .

 

Sean

Edited By sean logie on 12/12/2016 19:05:06

[mark smith 20Participant @marksmith20]

Sean , the chuck you linked to is only 1" according to the seller. I thought you said its 1 1/2" x 8 ??

[David Standing 1Participant @davidstanding1]

Posted by sean logie on 12/12/2016 19:01:07:

the gauges tell me that the threads are 7G 1/8-1/4 .

 

Sean

Can you be clear exactly what your lathe nose thread is? In the Q & A on the chuck listed on eBay you say it is 8tpi, but don't show the diameter of the thread, and the bit above doesn't make sense.

Edited By David Standing 1 on 12/12/2016 19:24:51

[David Standing 1Participant @davidstanding1]

 

Edit: Typing as Mark posted!

 

Edited By David Standing 1 on 12/12/2016 19:26:58

[mark smith 20Participant @marksmith20]

Sean, from what ive found out your spindle nose should be the same as Boxford, that is 1 1/2" x 8 whitworth (BSW),

And this was mentioned on a forum from a guy who owns two of these Fortis lathes.

So all you need is a 6" 4 jaw such as the one i linked to above (£66 including shipping) and a suitable boxford back plate. I would just buy one around 4" diameter and with the boxford thread but no screw holes(around £20).

If your register is slightly small on the backplate simply mount the backplate on your spindle backwards with a spacer so you could turn the register . (though according to the guy on the forum i mentioned boxford stuff should fit directly onto the spindle nose,so may be no need for it)

Turn the register on the backplate to fit the register on the chuck. Then just drill and tap the back plate for the four mounting bolts.

[sean logieParticipant @seanlogie69385]

Thanks Mark ,very interesting, was the forum .

Sean

[sean logieParticipant @seanlogie69385]

Mark would the 8″ the guy on ebay is selling be too big .

Sean

[mark smith 20Participant @marksmith20]

Sean, the chuck you point to on ebay won`t fit your lathe as its Myford 1 1/8" x 12 direct screw on.

The one i pointed to is the same but needs a boxford back plate which you would have to purchase seperately.

£66 for the chuck i point to and £20 for a back plate comes to £86 which is £24 cheaper than the one your looking at.

You`d need a chuck key or two but very easily made up from a couple of bits of scrap round bar.

Hopefully all you`d really need to do would be skim the back plate register to the size on the chuck then drill and tap four holes for the mounted machine screws. You would also learn something in the process .

 

An 8" wouldnt be too big for your lathe as its 12" swing but you would still need to fit it to your 1 1/2" x 8 BSW spindle nose.

You could use a 6" 4 jaw and get a faceplate if you need to turn anything bigger  which is what i do. I have one of these:

http://www.ebay.co.uk/itm/genuine-BOXFORD-LATHE-FACEPLATE-WILL-FIT-THE-AUD-BUD-TUD-lathes-/201746543751?hash=item2ef907f487:g:BL8AAOSwux5YTV9J

Edited By mark smith 20 on 13/12/2016 11:14:13

[sean logieParticipant @seanlogie69385]

I’ve ordered the backplate from rdg ,in the middle of negotiations with the chuck .

Sean

[mark smith 20Participant @marksmith20]

Which back plate did you order and which chuck?

[sean logieParticipant @seanlogie69385]

The two links you gave me .

Sean

[mark smith 20Participant @marksmith20]

Ok Sean, let us know when you have the back plate and/or chuck.

The register on my chuck is 82.5mm so when you get a chuck you may have to reduce the turned section on the backplate down to match your chuck (which may be the same as mine or slightly different)which is easy as long as you go slowly and keep checking for a reasonably tight fit..

[sean logieParticipant @seanlogie69385]

Cheers Mark and thank you for all your help. Which forum did the guy have the two fortis lathes . They seem to be quite rare .

Sean

[mark smith 20Participant @marksmith20]

HI Sean, its the same guy who posted on your Steadall thread, called Robert Hamblin who i think is in New Zealand. He made the comment back in 2008 on the practical machinist forum. He said the Boxford nose is the same size and that none of the Clausing spare parts fit the Fortis lathes.

[sean logieParticipant @seanlogie69385]

Hi the back plate arrived today and it doesn’t fit it’s too small. I’m going to add some photos a nd a rough sketch of my dimensions of the spindle and threads .

Sean

[peak4Participant @peak4]

Sean, I don't know if it's of any interest to you, but Tony over at Lathes.co.uk actually has photos of your actual lathe on his web site. You can tell by the blue paint spot on the brass thread cutting chart.

He also has a set of 3 manuals appropriate to it See Here. but do make sure I'm not misleading you, as these are for the Clausing 100.

He was a friendly enough chap when I bought some stuff off him many years ago, so I'm sure if you linked to the actual photos of your lathe on his site, he would be able to assist with some copies of the original manuals.

[mark smith 20Participant @marksmith20]

Hi Sean, sorry to hear , are you able to send the back plate back? i think RDG have a 7 day returns policy.

Looks like you have a 1.75" x 8 thread, do you know when your lathe was built approx.??? Apparently Clausing 4900 series lathes made in the 1960`s had that larger thread.

Lathes .co.uk do sell the 1 3/4" x 8 back plates for Smart and Brown sabel lathes which have that size thread but they are expensive..

 

Edited By mark smith 20 on 17/12/2016 19:08:44

[sean logieParticipant @seanlogie69385]

I wonder if the back plate can be made to suit the 1 3/4 8 thread

Sean

[mark smith 20Participant @marksmith20]

Sean you could thread it internally but its a bit harder than outside threading. What is the total depth of the back plate ?

Is it over the 1.6" depth you need?(according to your measurements.)

You need to bore out the back plate  right through somehow to 1.5" ,then you could thread it  for 1 3/4" x 8. You could then screw it on the spindle nose and machine the register.

Edited By mark smith 20 on 17/12/2016 19:44:21

Edited By mark smith 20 on 17/12/2016 19:49:01

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