Burnerd 3 jaw chuck

[exairman]

My Burnerd 3 jaw griptru chuck no longer does, grip true that is. The jaws appear to be bellmouthed and the first 6mm of small diameter bar is not held making it impossible to machine accurately. This is probably due to years of use and misuse. I was wondering if it is possible to have the jaws reworked l notice that the jaws have a serial number which ties in with the one on the chuck body so it would seem that new jaws are out of the question.

 

[abby]

Depends whether your chuck is imperial or metric.
New jaws are available for metric chucks but I could not find new imperial jaws except , strangely , soft ones.

 

[BaronJ]

Depends whether your chuck is imperial or metric.
New jaws are available for metric chucks but I could not find new imperial jaws except , strangely , soft ones.

Get ready to donate an arm or a leg, possibly both !
I got a price for a set of jaws for mine... Over £300 + vat

 

[necchiom]

Get ready to donate an arm or a leg, possibly both !
I got a price for a set of jaws for mine... Over £300 + vat

Whow! Are they made of gold Baron? Are they for you ML7 or for a larger chuck?

 

[mu38&Bg#]

Why not just true them? It's often talked about using a tool post grinder, but the right carbide boring bar will also get the job done. Make sure the lathe is turning a straight bore before doing so.

 

[exairman]

Given a price like that a new chuck would seem a more viable proposition. Comos do a Myford compatible chuck for a lot less than £300 food for that yes?

 

[exairman]

Sorry about that folks the firm with the new Myford 3jaw chucks is Chronos, it,s less than a £100 including internal and external jaws. Be interested to know if they have serial numbers on them!

 

[necchiom]

Sorry about that folks the firm with the new Myford 3jaw chucks is Chronos, it,s less than a £100 including internal and external jaws. Be interested to know if they have serial numbers on them!

In my opinion would be cheaper to buy a new chuck.
For hobby works I prefer cheap chuck, and replace it every 3-4 years, than eternal more precise but expensive one....

 

[BaronJ]

Whow! Are they made of gold Baron? Are they for you ML7 or for a larger chuck?

Yes for the S7 3.5" P&B chuck as supplied by Myford.

When I recovered from the shock I went and bought a 5" MII chuck and backplate. I ought to have done that in the first place.

Quick update:
I've now acquired a suitable piece of steel plate to make a fixture for machining three tool holder blocks. Whilst I was at it I also got a chunk of aluminium to make some locating lugs for the rotary table. I could do with getting another cheap four jaw to fit on it.

 

[BaronJ]

Sorry about that folks the firm with the new Myford 3jaw chucks is Chronos, it,s less than a £100 including internal and external jaws. Be interested to know if they have serial numbers on them!

Hi,
Its my understanding that they do. It would be very interesting to see what the quality and accuracy is like. Certainly I can't see them being upto P&B standards.

 

[exairman]

Why not just true them? It's often talked about using a tool post grinder, but the right carbide boring bar will also get the job done. Make sure the lathe is turning a straight bore before doing so.

This is a thought but ifyou were to do this would ot the jaws now have a radius on their tip? Also when you were to close the jaws their sides would meet before the tips touched and you would be left with the problem of not being able to hold small work. However, if it wre possible to have the tips ground parallel and a piece of hss steel fixed to it and then ground to the original profile, that would be great solution but does anyone do that? Regards exairman

 

[necchiom]

Hi,
Its my understanding that they do. It would be very interesting to see what the quality and accuracy is like. Certainly I can't see them being upto P&B standards.

With Chronos price list in mind, I guess they are made in the Eastern part of the world... Same size of chucks really "Made in Italy", in Germany and I suppose in UK..., cost at least the double.

 

[abby]

Dont know if this link will work but soft jaws are readily available from Cromwell tools at a reasonable price.
https://www.cromwell.co.uk/KEN4901030K

 

[mu38&Bg#]

This is a thought but ifyou were to do this would ot the jaws now have a radius on their tip?

The radius is really only a problem if it's smaller than the work being held. If you're worried about marring a finished OD that's larger than the jaw radius a piece of paper usually prevents it. I trued master and top hard jaws on an old Burnerd 6" chuck at something over 1" diameter and have used it for a few years since. Everything is dandy. If you do decide to true it. Take the time to take it apart and clean it prior, you don't want dirt in the scroll and master jaws.

 

[mu38&Bg#]

Soft jaws have their applications, but I can't see buying soft jaws where the chuck doesn't have top jaws. Maybe for a job where you have many to make, but otherwise soft jaws are consumed fairly quickly.

 

[BaronJ]

This is a thought but ifyou were to do this would ot the jaws now have a radius on their tip? Also when you were to close the jaws their sides would meet before the tips touched and you would be left with the problem of not being able to hold small work. However, if it wre possible to have the tips ground parallel and a piece of hss steel fixed to it and then ground to the original profile, that would be great solution but does anyone do that? Regards exairman

Hi Guys,
I've never actually done it but have seen it done. A steel disk is bored out so that it fits over the outside of the jaws and then the jaws opened up to grip the disk. The inside of the jaws are then ground whilst the chuck is rotated at a fairly low speed. The lathe on which I saw the jaws being ground had a 9 or 10 inch diameter chuck, actually a Herbert 5A. With the coolant spray you couldn't tell that any grinding was taking place, it was very quiet. The noise from the gears drowned out any grinder noise. The actual grinder motor was mounted on the turret with a flexible shaft driving a small abrasive wheel.

 

[BaronJ]

Dont know if this link will work but soft jaws are readily available from Cromwell tools at a reasonable price.
https://www.cromwell.co.uk/KEN4901030K

None of those will fit a P&B chuck as fitted to a Myford S7 or ML7 lathe.

 

[BaronJ]

Soft jaws have their applications, but I can't see buying soft jaws where the chuck doesn't have top jaws. Maybe for a job where you have many to make, but otherwise soft jaws are consumed fairly quickly.

I agree with your comments in the other post. Cleanliness is vital if you are going to go down that route.

As far as soft jaws go that is an easy one ! Make a set that fit over the existing jaws and throw them away when worn out. I use aluminium for mine.

 

[abby]

The soft jaws sold by Cromwell fit MY P-B chuck on MY Myford ML7 , I posted this link because it was the only place I could find ANY jaws for imperial sized Burnerd chucks , if they haven't got your's that's bad luck.
Please explain how to fit an aluminium set over existing jaws , I can't see how you could fix them in place. The whole point of soft jaws is that they can be machined for a particular job , taken out and put back in the chuck without losing the initial accuracy. I have several sets , each for a particular production job that is too large for a collet.
You don't need to bore out a steel disc , the outer race of a large roller bearing is easy to obtain , very accurate and will do the job admirably , however the reground jaws will only be truly accurate at the ground diameter as the forces on the jaw teeth and scroll will be reversed from those applied when in actual use. Even so badly bell mouthed jaws can be improved using the method.

 

[Charles Lamont]

I regound the bell-mouthed jaws of my Griptru a few years ago and it made a vast improvement. I followed pretty much exactly the advice given here:

http://www.homemetalshopclub.org/news/aug04/aug04.html

The time consuming job was making a decent toolholder for the die grinder, shown at the bottom of this page (I have linked to this from HMEM before, but it is relevant here):

http://www.charleslamont.me.uk/iqc_toolpost4.htm