Remove Seized on chuck ??

[micktoon]

 Hi Oz , thanks for that I have ordered them as think I will have trouble setting correctly without them.

 This is the story of how the chuck was removed

I already had a boring bar I had made and a quick change tool holder that would hold it. The basic plan was to drill the end of this boring bar and make a parting tool incert to fit in the end of it that  would align with the very rear edge of the backplate just short of where it mated with the spindle shoulder.

Thes shots of making the bar are in my mate Daves workshop, using hid Kerry AG lathe and Emco FB2 mill, cheers again Dave.
Centre drilling the bar


Drilling the bar for the incert to fit


The incert test fitted in the bar, this was something Dave had lying around so just needed altering as it was already roughly what we needed.


The side of the bar needed milled of for clearance and the other side was milled flat, drilled , tapped M6 and grub screws used to lock the incert in place


This is the new tool in the holder lined up for action


Note the DTI this was to gauge how far the tool advanced to make sure it did not mark the spindle


So far so good , just going slowly, once it was only a fracion to go, I tried putting bolts back through the backplate and the slightest of taps loosened the B*****d


This is the backplate after its surgery, just as planned , the spindle not touched but the stress locking the thread releaved so free


The spindle survived the ordeal


This it the blow hole in the casting that has been threaded, soon as I saw this I remembered it was like this before, it was like this when the chuck came with the lathe and has been used many times, do people think this is what will have caused the problem and is it savable by filling with metal putty and reshaping or bin it ? bearing in mind its either hassle or expensive to get a six inch backplate.



So at least someone else will be able to use this method to remove a locked on chuck without damage .........the back plate has enough 'meat' to be used again if its repairable too.

Cheers Mick

[vtsteam]

do people think this is what will have caused the problem and is it savable by filling with metal putty and reshaping or bin it ? bearing in mind its either hassle or expensive to get a six inch backplate.

I think either a piece split off in that area or a piece of swarf got caught unnoticed in the cavity there.

I'd probably fill it with JB Weld metal filled epoxy and re-cut the thread, but that's just my nature, salvaging old metal if at all possible. Not necessarily good practice!

Also a great fan of the qualities of JB Weld in relation to cast iron

But it seems to me, if there are no holes for swarf to collect, and the thread is again smooth it is unlikely to happen again.

And now with a special tool to free it..........

[lordedmond]

 Mick

I would bin it ,buts that's me

There's a nasty crack to the left of the main cavity a couple of threads further out.

How many more threads are cracked ,looks like it has a lot of inclusions and stress fractures

But that is bases on what I see ,what does the mark one eye ball say , a good dig round with a brass probe may show up any more

It would be a right old pain in the rear if it happens again

Stuart

[awemawson]

I'm in the 'bin it' camp. Life's too short for this sort of thing to be repeated. Buy a steel backplate blank to avoid future issues.

[Fergus OMore]

In my earlier 'Number4' in this saga, I referred to two different threads on my Myford bit. I think that it was a Dividing head spindle- but no matter. Two issues arise- not one.

There is the question of the register which has not been addressed.  The threads on the chuck are academic and secondary . All that the threads do is hold the chuck onto the spindle. For what it is worth, you could file off the tops of the crests- so long as the chuck holds its register- and doesn't rotate off.

Sorry folks, but I did all this malarkey many years ago on an old ex-wartime Pools Major which probably none have heard about.

Regards

Norman

[awemawson]

Sorry folks, but I did all this malarkey many years ago on an old ex-wartime Pools Major which probably none have heard about.

Regards

Norman

Sadly I have 

[vtsteam]

Can I retract my earlier opinion? 

I thought about restoring the thread after the epoxy fill and decided that picking up the thread and re-cutting, or making a tap to suit, etc. would be as much work as cutting a new thread, and I know in that case I'd just be visiting Lester at the Old Tyme machine shop and buying a lump of steel for maybe $20 or $10 depending on the stories swapped, to make a new plate by preference. Because that would be fun for me!

But I wouldn't bin the old one. Cast iron is a valued scrap material for building something else, or re-melting and pouring it.


ps. next time I'm at Lester's I'm going to have to remember to bring a camera and post some pictures here. They will sort of look like Jackson Pollock paintings in various shades of black, in which you can just make out the shapes of ancient machinery and tooling and materials. As if arranged by a tornado.

[Manxmodder]

In my earlier 'Number4' in this saga, I referred to two different threads on my Myford bit. I think that it was a Dividing head spindle- but no matter. Two issues arise- not one.

There is the question of the register which has not been addressed.  The threads on the chuck are academic and secondary . All that the threads do is hold the chuck onto the spindle. For what it is worth, you could file off the tops of the crests- so long as the chuck holds its register- and doesn't rotate off.
 
Sorry folks, but I did all this malarkey many years ago on an old ex-wartime Pools Major which probably none have heard about.

Regards

Norman

I agree with Fergus here. There are 2 separate potential problems that caused the backplate to jam.

If the thread was the cause then galling or tearing of the thread would be evident. If the thread had galled then relieving the axial force as Mick has done with the parting tool would not have enabled him to undo it so easily as he did.

Looking at this now,I think the locking on problem has been in the area where the register face meets the spindle shoulder .  The use of JB weld or metal repair putty is a very acceptable and well documented method of repairing voids or blow holes in castings and threads.....OZ

[Fergus OMore]

Thanks Oz for supporting my views. There seems to be  a need to check exactly how round and how parallel the register on the spindle is. Again, there seems to be a need for the mating surfaces on the chuck body part of the register. It suggests making a go and no go gauge. If it jams somewhere, it can be belted out. Obviously I am not 'au fait' with Mick's lathe but making up such elementary test gear goes a long way to avoiding the same old problems arising- again and again.

Clearly it is not in the book for run of the mill model making but my suggestions are commonplace in an inspection department.

Me, I'd like to know if my memory is still in one piece. It's a Looooong time since I played with a guessing stick- sorry , slide rule.

Meantime, cheers.

Norman

[vtsteam]

But the register wouldn't have changed suddenly -- this chuck had been put on many times before with no problems, and this time was put on lightly, cleaned, oiled and not run against anything. A register problem would have acted differently, I think. Maybe it was a combination of things.

[Fergus OMore]

I'm merely reading the 'evidence' as reported. What there is an increase of heat which could alter cast iron and steel dimensionally. What is normal is that cast iron is cut roughly to size  and then left to the elements to 'weather' before finish machining - and that finish machining is not the finish. Lathes 'move' and move.  Somewhere, there is a note of someone building a mill. When I built a original Westbury, I had it all 'ticketty- boo' until I split the head stock- and it seized. I made a 'first 'Quorn' and split it- and had to make a second casting.  The late George Thomas reported that his first Staking Tool pair of arms moved and now there is something called 'Mark11' castings.
 Sadly, no one seems to know when and why. about things but I'm not surprised any more.

I'd merely want to avoid or minimise future problems for our poster.

Regards

Norman

[mcostello]

I cannot help to believe that any kind of epoxy on the threads MIGHT come loose and make another similar problem when least wanted.

[Manxmodder]

Epoxy putty,JB Weld or Belzona are all epoxy based metal repair pastes specifically designed for this type of repair.

Providing the part to be repaired is properly degreased and has a good surface key then no problems should arise from this method.

I have also made and used my own metal repair pastes using graded cast iron powder,brass powder, and bronze powder mixed with epoxy resin for various repair applications over the years.....OZ.

[vtsteam]

JB Weld is also rated at 500 F, I believe, considerably higher than most over-the-counter epoxies which soften above 200-250 F. I've done some miracle repairs with it, and once built a thermostat housing for a Lister type diesel generator using the stuff instead of welding. It's still going 6 years later. Also a casting repair that has lasted 12 years in the pivot bushing area of my John Deere Model M tractor. The bushing area had worn egg shaped after wearing through the original bushing. I rebuilt it to original round and added a new bushing.

[PekkaNF]

Is a little armchair engineering allowed?
* As stated earlier this thread does not locate the back plate - would it be possible to turn thread off and replace the tread with flange/bushing type thread insert on the nose side of the back plate? That would keep the register intact, put the cast iron on compression when tightened and prevent rotation if this insert is pinned, glued or fastened to back plate. The question is: Is there enough room for it?

JB weld and such:
* To my knwledge threads are not leaded evenly and pretty often only few threads take up most of the load, that suggest that thread part is pretty unevenly loaded member and discontinuities will create probles?
* JB welds et al. has very much lower strengt than cast iron, I think here it cover the blowhole and reduce ingress of dirt, but probably not doing much to prevent the cast iron from disintegrating next to it (fault). I think that It's pretty probable that same thing could occur again when a part of thread next to blowhole would collapse.

Pekka

[awemawson]

I cannot quote chapter and verse, but I distinctly remember John Stevenson on another forum asserting that the thread AND the register hold the chuck concentric, as even a loosely fitting thread, when under tension, settles on the pitch circle of male and female forcing concentrically.  John is an engineer who's views I respect, and he has a huge wealth of practical experience.

[lordedmond]

 My take on what happened on further inspection of the pics is

That a small piece of the casting in the thread region broke loose and jammed up the thread thus causing a cam like lock or one way clutch so to speak

Parting part way through relieved the tension just enough to move the backplate thus relieving the cam lock

IMHO I cannot see the parallel register had any part to play In the jamming/locking of the back plate

As for the JB Weld repair yes it's good stuff I do use it but the parts do need to be clean and oil free it would be one hell of a job to ensure that was the case this case , a good soak in trike followed by a ultrasonic clean but the can you be 100%sure. It's a none starter for this application

Stuart

[PekkaNF]

I cannot quote chapter and verse, but I distinctly remember John Stevenson on another forum asserting that the thread AND the register hold the chuck concentric, as even a loosely fitting thread, when under tension, settles on the pitch circle of male and female forcing concentrically.  John is an engineer who's views I respect, and he has a huge wealth of practical experience.

I agree about John Stevenson, he pretty much knows what he is talking about.

I just see here two surfaces that (radial and axial) register back plate, I assume that the tread is dimenssioned not to interfere with rest of the register. I could be easily wrong, there could be an additional aspect here I'm not aware. I have been reading myford register/gauge plug turning material and some steps are not very clear to me - I have been assuming that the great care used to spend on making thread was to ensure that the thread pulls backplate squarely to spindle nose I.E. not to offset it anyways.

Pekka

[Manxmodder]

I cannot quote chapter and verse, but I distinctly remember John Stevenson on another forum asserting that the thread AND the register hold the chuck concentric, as even a loosely fitting thread, when under tension, settles on the pitch circle of male and female forcing concentrically.  John is an engineer who's views I respect, and he has a huge wealth of practical experience.

Andrew, your thinking is correct about the threads self centering axially about the PCD when tension is applied through tightening.......OZ.

[micktoon]

Hi Lads, well this topic has certainly got some banter going anyway  I am not going to re use this backplate just from common sense point of view really , I might have been lucky not to have damaged the spindle threads and might not be so lucky next time, if this did happen I would be kicking myself  . If it was the last one in the world and you had to make a part for the boat to be able to escape the desert island you were trapped on I dare say it could be repaired with JB or what ever and it might also be fine for further use....................BUT I know my luck and do not want to increase my chances of hassle lol.
  So I will try to get a backplate , If I can not find one I will have to make one, I have my four jaw chuck to use the lathe anyway. As for the threads and the register, I had thought the register was what held the cuck in the correct position as it was screwed on and the threads in effect were only keeping the chuck on the register and not in themselves actually putting the chuck into position.

  Cheers Mick

[chipenter]

Tony at lathes.co.uk has backplates on stock for £65 .

[doubleboost]

The register is the bit that gives the chuck / face plate ect its accuracy
The thread can be slack (ish)
I have a drive plate that wobbles up the thread but always runs dead true once tight
John

[awemawson]

I think John Stevenson's point was that even a thread that wobbles as you describe when not under tension will pull itself concentric when tensioned.

[Manxmodder]

Tony at lathes.co.uk has backplates on stock for £65 .

 If that price is for a cast iron blank that needs machining then it is very expensive.

I think I'd be sourcing a piece of steel bar butt end or looking for a suitably sized car flywheel from the scrappy than pay that.....OZ.

[stig]

if its just a blank then they're available far cheaper off evilbay

smaller item in link below as example
http://www.ebay.co.uk/itm/300921529064