MadModder
Gallery, Projects and General => How do I?? => Topic started by: micktoon on June 04, 2014, 11:06:50 AM
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Hi all , I am hoping that someone can help with a problem of a chuck that is stuck on my lathe spindle. I am on the finishing jobs of my rebuilt Harrison L5 and had screwed the chuck on with very light hand pressure only after cleaning both spindle and chuck then applying light oil. I have not even turned anything in the lathe but when I have come to remove the chuck its stuck fast. Proper stuck fast too.
So far I have tried .
large hex bar in the chuck and big spanner on it, tapping the spanner to shock it and jerking spanner with the gear train locked so the spindle can not rotate.
The usual realeasing oils etc, left over night and also repeated after heat applied
Removing the chuck from the backplate , incerting 3 bolts through backplate holes and levering with 3 feet long 1 inch bar , hitting said bar to shock
Heating the backplate up with propane torch and trying to shift while hot , then when cooled again, tapping all around trying to break seal
Replacing chuck and chucking large hex bar then trying to loosen with large socket and windy gun. ( only thought of this after the other attempts )
The force used so far and the hits have gradually reached the point where something is likely to break if any more force used so looking for ideas. It would seem totally impossible that it has become stuck this tight. I know 100% the threads are clean, there is film of light oil and the chuck has not been tightened other than by light hand pressure. I am assuming the rear face is seated against the spindle shoulder and the 'lock' is between this and the threads, will this be the case ? I think it must be as this chuck has been on and off many times before and I know the register is clean and oiled as are the threads.
Here are some photos of what I am dealing with.
This is a samller bore Harrison spindle of the exact same design showing the thread, register and shoulder, then the chrome cover, note the shoulder sticks out the chrome cover a small amount. The actual one on the lathe is clean and spottless and oiled.
(http://i1167.photobucket.com/albums/q631/micktoon/Madmodders%202014/Harrisonstuckchuck010.jpg) (http://s1167.photobucket.com/user/micktoon/media/Madmodders%202014/Harrisonstuckchuck010.jpg.html)
This is the same design backplate that is stuck on my spindle, showing the register and rear face that is butted tight to the shoulder on the spindle.
(http://i1167.photobucket.com/albums/q631/micktoon/Madmodders%202014/Harrisonstuckchuck011.jpg) (http://s1167.photobucket.com/user/micktoon/media/Madmodders%202014/Harrisonstuckchuck011.jpg.html)
This is the stuck backplate with the bolts through it , that the large bar was acting against both jerking and hitting with the gear train locked stopping the spindle rotating, I have gone to maximum force with this , it would have shifted a truck wheel nut in my opinion.
(http://i1167.photobucket.com/albums/q631/micktoon/Madmodders%202014/Harrisonstuckchuck005.jpg) (http://s1167.photobucket.com/user/micktoon/media/Madmodders%202014/Harrisonstuckchuck005.jpg.html)
This is a shot to show the spindle shoulder just visible coming out the chrome cover, the backplate is mated up to this. I have a parting tool in the tool holder to show roughly what a plan might be ?
(http://i1167.photobucket.com/albums/q631/micktoon/Madmodders%202014/Harrisonstuckchuck007.jpg) (http://s1167.photobucket.com/user/micktoon/media/Madmodders%202014/Harrisonstuckchuck007.jpg.html)
The red small tube is pointing to the spot that I could with a slim parting tool slice into the backplate just shy of where it mates to the spindle shoulder and releave the tension or compression causing the locking.
(http://i1167.photobucket.com/albums/q631/micktoon/Madmodders%202014/Harrisonstuckchuck006.jpg) (http://s1167.photobucket.com/user/micktoon/media/Madmodders%202014/Harrisonstuckchuck006.jpg.html)
So really what do peolle think is causing the thing to be seized, what I think some sort of hydraulic type lock or taper type lock between the backplate mating to the spindle shoulder or could it be the threads ? they are clean and oiled. I would really like to svae tha backplate as a hard job to find them for decent price and do not want to have to make another one, I do not want to damage the lathe in any way.
All Myself and a friend can come up with is to maybe drill very small holes in the backplate so releasing fluid could be directly introduced into the threaded area ( if that is what the problem will be) Or to make a special parting tool so it could part away the very end section of the backplate nearest to the spindle shoulder yet miss the spindle by a thou or two, I could also make the tool so it could not go in too deep and mark the spindle as I have a smaller spare backplate with the exact same register to measure.
Any help most appreciated
Cheers Mick
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Mick,
It probably needs a shock to remove it. To avoid damage, I would put a longish piece of wood in the three jaw, and clout it with one solid blow rather than try to lever it off. If all fails, the wood rather than anything else will go.
Regards
Norman
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Mick, now I know you do fine work, to get a wringing fit like that on a restoration job!
Any urchins wandered into the shop, with super glue?
Wife been smiling to herself lately?
I vote for Fergus' shock treatment, too.....
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Mick
With the methods you have tried ,and respecting your skills
The only way out IMHO is to turn the thing off to just larger than the register and threads, much safer than shock loading the gear train ect.
Some have had success with clamping the spindle with a stout wooden clamp and using that to hold it fast while you give it some wellie , but it's something I have not tried
Stuart
Btw great restoration
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No 'toffee hammers', at least you want a club hammer. You have to frighten it- not vice versa.
If you are squeamish, jam a wooden wedge to hold the spindle while you 'talk to it'.
I got one of these bastard Myford backplates which had been tapped 60 degree instead of 55 Whitworth- that is what I did.
It's a doddle compared to moving a stuck clutch plate on a tuned Mini Cooper :drool:
Norman
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Hi there, Mick,
Sorry to hear of your problem especially after all your work and with the lathe looking so good!
Could you make one of those gizmos that grip in the bore at the rear end of the spindle? With a tapered plug drawn into a tapered bore by a draw-bolt to expand it in the lathe mandrel bore. Like the mandrel handles some folks use for threading.
If that could be made to get a firm enough grip on the lathe mandrel, it would avoid using the gears to lock the mandrel and risking the dreaded toothe-ache!
If I remember rightly, you do have another lathe?
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Was the chuck at a different temperature to the spindle when you put them together?
Invert an HSS tool you care little for but is beefy in tool post, run lathe slowly in reverse, take an intermittent heavy cut on something suitable in scrap bin. Have 'chuck board' under chuck for when it unscrews, hover hand / foot or whatever over brake and watch like a hawk
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Mick,
with the chuck attached can you clamp a section of hex bar in the jaws and then use an air powered impact wrench like they use for car wheel nuts to undo it off the threads?
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Strip it back to the backplate as in your third picture and use heat, don't piss about with a blowlamp either use oxy/acet or a tig set up will keep the heat more concentrated and it should spin off no problem.
Mike
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I would go for the running in reverse using the cutter or the impact first.
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Hi lads thanks for the in put so far .
Stig, I have tried the windy impact gun on the about 30mm hex bar no luck, it is good windy gun and will shift most stuuborn bolts on Landrover etc.
Mike , I have ran out of oxygen , I dont want to damage the backplate by tig ing if I can but will if I have to.
Andrew, both lathe and chuck have been in the same place forever so will have been same temp, the inverted tool is good idea and I can probably try but to be honest
I have had real force applied to the backplate , I would say lots more than a cutting tool would produce ?
Norman, when I say I have give it some welly I mean really I have large copper hammer full belt onto inch bar wedged through M12 bolts through backplate with spindle locked via gears and the 3 feet long bar also jerked down with full weight until its flexing and it was a hardened steel bar. if the lathe was not frightened it must be hard as nails lol
Stuart, the wood clamp idea had crossed my mind its on the possible list but hoping not to have to make something complicated.
Pete, I think your idea gets the vote so far , mainly in part , what happens when this happens again, also as you say cutting all gears etc out the chain..........the last thing I wanted was another bloody project to make something to do a job......... but I should have known lol
Thanks again for the ideas so far................. so does anyone think they know exactly how it has become so stuck from putting on by hand, what is stuck to what ??
Cheers Mick
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Strip it back to the backplate as in your third picture and use heat, don't piss about with a blowlamp either use oxy/acet or a tig set up will keep the heat more concentrated and it should spin off no problem.
Mike
I agree this is the way I would go. Lock the gears and use a wooden wedge as well ! Use a long bar as a lever and apply some rapid intense heat around the backplate but keep away from the spindle bore. You want to expand the backplate not the spindle. Apply a high pressure to the bar whilst you heat it up.
I would suspect that the backplate was probably hot when it was screwed on.
HTH.
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Bummer....Can't really use too much impact because fear of brineling the bearings or breaking gears. Propably impact wrench with limited pressure would be least detrimental. Can't use too heat, because of the seals, bearings, hardened parts etc.
To me intermitent cut + some sort of bar inside the chuck to prevent the chuck (or back blate) bouncing around sounds worth trying, maybe a little heat from hot air gun outside the back plate and then cold spray inside the spindle .... it's not much, but combined effect might be enough. Here we probably want maximum diameter and plenty of extension from the chuck to make it walk out of the lock. You have penetrating oil, you need a little movement there.
I have had some joints I was pretty sure will not come out without a angle grinder but few days of penetrating oil and heat/cold cycle got them eventually undone. I know this is not rust, but situation is pretty much the same.
I'm really really reluctant to hit anything on lathe spindle if it has AC-bearings or such.
Pekka
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Id say awemason might have touched on the answer, if the chuck and register were hot and cold compared to one another then a snug fit could easily have become an interference fit once they equalise.
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Do not engage the gears - hold the spindle in neutral with a split bar gripper thing inserted into the rearof the spindle.
protect the bed with wood so nothing can hit it.
bolt a short bar to the back plate (get every thin a stiff as possible) and hit it hard n fast with a good size hammer .
Or
just machine it off - it would be a real shame to damage that beautiful restoration.
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As to causes, I was half joking about wringing, but maybe?
http://en.wikipedia.org/wiki/Wringing_%28gauge_blocks%29#Wringing
The other thing I was thinking of was an unnoticed cracked thread working loose and jamming across in a way that the more pressure applied the greater the jamming force.
In tractor restoration work one thing sometimes written about is trying to turn in the tightening direction first to break loose a really bad lock.
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sitting quietly reading this with interest and finally V T said what i'd been thinking...tightening first has always worked for me but then ive never had a problem this size before.. I would'nt imagine it could get any tighter so i'd give it a go,,1 whack to tighten followed by a bigger one to loosen,,but use the hand turning shaft in the back end of the spindle..to brace against....
as for causes,?? no idea,, but if theres a tight vacuum in there would a very small hole towards the shoulder or even the thread help break the seal??
...Mike..
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Steve, the wringing theory is worthy of considering but I honestly don't believe that there is anywhere near sufficient cling to resist the type of force Mick has been using to try and remove the threaded chuck plate.
All the twisting force and shock that Mick has applied would have easily broken the attraction/bond of any wringing that may be potentially caused by oil on the 2 faces.
The easiest way to separate 2 wrung surfaces is to apply sideways shearing force to slide them apart which is exactly what Mick is doing by trying to unthread the chuck plate.
I do wonder if the soft iron thread inside the backplate has torn or galled a bit when it was screwed on,or if the thread in the backplate has run up against the shoulder of the spindle register and caused the lead thread to deform slightly.
The spindle nose/thread and backplates on my Harrison are the same as Mick's and to remove a chuck I use a 2 foot long piece of 1" square box section gripped across the jaws and with the lathe in a low speed gear for resistance normally only requires a good thump with the palm of my hand to break free.
There have been occasions after some heavy turning has tightened things more than normal the I have had to resort to using the copper mallet to strike the end of the piece of box section and a couple of very firm blows have been required to get things moving.
I wouldn't bother with air driven impact guns because the mass of the chuck or even the backplate is such that the relatively small inertia force from the gun is absorbed by the mass.
Mick, by all means try some heat and a couple of thumps with the mallet again,but beware of transferring too much heat into the head bearings.
This may very well be a situation where some very careful machining work is the only viable option to remove the backplate.
Another option I would seriously consider is splitting the backplate thread along its length.This would require at least one groove or slit be cut in the backplate parallel to the spindle and down as near to the crest of the spindle thread as possible,then a wedge or chisel used to open the slit and produce a break along the cut line axis.
Mick, beware that because neither the spindle or backplate are hardened if the thread has galled then just unscrewing it forcibly could tear and do a lot of damage to the spindle thread,that's why splitting it may be the best option. If you need any comparative measurements from my spindle for reference just ask......OZ.
Edit to add: your cutting the register boss with a parting tool idea also has merit,but just make sure no cast iron swarf or dust enters the small clearance gap between the chrome bearing cover and the spindle.
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Off topic for a second, but ..
Mick your lathe restoration is looking magnificent..I love it... :drool: I really feel for you, getting a monster snag like this especially at this stage when your so close to completion... :bang:
best of luck...
...Mike..
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I'm not sure I can offer any useful advice but I can offer sympathy.
If the chuck wasn't fully screwed home and the lathe started it might have seated with a jerk which can get things fairly tight.
It seems to me that the main difficulty is applying enough force without damaging the rest of the lathe - in that case pulling the spindle out might be the best option - you could make suitable clamps to hold it without damage.
The other option is to sacrifice the back plate - which will cover your beautiful restoration with loads of nasty cast iron dust.
Good luck.
Russell
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I am merely guessing but the bull wheel etc will be or should be held on the spindle with a long key.
This is the bit that will take the brunt of the clout. The rest of the gears etc can be locked with wooden vee wedges forced between the gears and the headstock casting. ( This is how it goes on a Myford anyway)
If you can put a long steel rod neatly onto the 3 backplate, you can clout it loose.
OK, you can bugger the keyway mentioned and you might need a very long scaffolding pole but it should 'give'.
I recall using a scaffolding pole to release what should have been on at 140 lbs.feet and literally jumping on it with all of 11 stone massively constructed masculinity( well!) but it did give.
Brute force and applied ignorance!
You know I was thinking of the screaming of tortured car body metal when pulled with a 'warwick' into alignment after a crash.
Best of luck
Norman
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Mick, I do have a 1" drive air operated impact driver you could use if you have a big enough air source - I run it off a road compressor. Big hex in chuck and suitable socket should eventually shift it. (Got it for various big bolts on farm machinery)
I still think that a heavy reverse interupted cut would do it
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I still think that a heavy reverse interupted cut would do it
yes, but think what would happen when it does ;-)
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Fergus OMore said:I am merely guessing but the bull wheel etc will be or should be held on the spindle with a long key.This is the bit that will take the brunt of the clout
Fergus, the spindle and sliding bull wheel are located on very beefy splines rather than a keyway,there is little likelihood of damaging either through high torque or shock......OZ.
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I still think that a heavy reverse interupted cut would do it
yes, but think what would happen when it does ;-)
Nowt if the chuck is holding a long bar that goes up it's spout - but as I said earlier, use a chuck board over the ways, slow speed, and hand / foot hovering over brake.
Might start with washing up bowl under chuck and pour a few kettles of boiling water over the back plate before starting (not forgetting to remove the bowl before running :ddb: )
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Mick, I do have a 1" drive air operated impact driver you could use if you have a big enough air source - I run it off a road compressor. Big hex in chuck and suitable socket should eventually shift it. (Got it for various big bolts on farm machinery)
I still think that a heavy reverse interupted cut would do it
Hi Andrew, as I said earlier my real concern with this approach being that the threads may have picked up and galled. Any forced effort to fully unscrew the backplate off could do dreadful damage to the spindle thread.
If Mick can get the backplate to undo just enough to be clear of the register shoulder and it is still tight to turn then it will be safe to assume the thread has picked up and galled and unscrewing it any further will only do more harm.....OZ.
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I'm just glad I've never owned a lathe with a threaded spindle mount. Only had L0 and D1-4 on manual lathes which don't potentially present this problem.
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Andrew, I absolutely agree with you,threaded spindles are the devil's work.
The worst of it being that Harrison offered the threaded nose as an option on the L6,the standard fitting being L00.
When Mick was doing the L5 restoration thread I did suggest that converting the threaded nose to taper fitting by means of an adaptor was something I plan to do to mine.
Seeing Mick's current predicament has further convinced me that a taper conversion is the way forward for me....OZ.
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Thinking of Tapers(Oz!) is there room to put in a wafer thin pair of taper wedges to marginally jump the threads onto another part of the thread and break or alter the galling. It is classic engineering where the crests of the threads are probably too high. and adding to the jam. It does reshape the threads -a tiny bit thinning them.
OK, it is hardly a time to lecture about the rounded crests and whatever they should be but it has been written about by others more expert than me.
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Oz, I think that's right, it couldn't be wringing force because unscrewing would put it in shear, where it is weakest.
Likewise I don't think it's any kind of suction force because of the same way it is being attacked -- suction can only be 14.7 lbs/sq in, which isn't much whe figuring the area involved, and it's oriented the wrong way to resist turning -- just like a suction cup on oiled glass -- you can slide it sideways relatively easily. And in addition, the threads apply mechanical advantage to breaking the seal in the axial direction -- plus the advantage of a 3 foot bar Mick used as a lever.
I don't think its suction or wringing.
That leaves galling in either register or threads as the only other possibilities. Since it went on easily, was oiled and cleaned, and wasn't tightened hard or worked while turning, the most likely problem is that something jammed in those areas that wasn't seen or felt, and did not inhibit screwing the chuck on, but only acted when trying to remove it.
For that mysterious circumstance, I can imagine a piece of thread with a crack in it, maybe in the backplate, not being noticed and staying in place when the chuck was screwed on. That would explain the ease. But then when unscrewing the thread piece is forced outwards and jams, like a latch lock. As more unscrewing pressure is applied the thread piece, being relatively soft, deforms in length, increases in width and becomes more like a plug. Expanding and locking the thread further with every increase in force.
That's about all I can think of considering the conditions things started with -- which would seem to have been ideal.
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If it is anything like that, galling in the threads, broken thread piece, or unnoticed plug of swarf, force can only damage the area where it is located if enough is applied to break the parts free. Only by damage can it be freed.
So if it is true, I would cut the backplate off, in hopes of saving the spindle.
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Don't forget that a thread is a wedge wound around a shaft, the leverage is like driving a wedge in between two not parallel surfaces, it can behave like a tapered cone on tooling .
I would humbly suggest warming up and a dead blow on a piece of wood across the chuck. unless you get the end of the spindle red hot, your not going to damage anything. I doubt very much that there is anything wrong with the thread. An oiled thread can lock on like an oiled taper.
Regards, Matthew
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Well Mick
is it OFF yet we are all waiting to see who came up with the working solution so we can file it away for our own use ( those of us that have a threaded spindle nose that is )
Stuart
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I reckon Mick mixed up the oil can and the Loctite bottle when he 'oiled' it :lol:
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Andrew, on a serious note I have been considering some of the extra strong loctite retaining compound as a possible means to retain a threaded to taper adaptor conversion on my L6 spindle. Many a true word spoken in jest......OZ.
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Hi all , thanks again for all theadvice and for the offer of 1inch windy gun too Andrew.
The Ba##### is off after my mate Dave and myself had more tries we have then made a special parting tool and went with the plan of parting a slit in the back plate just a fraction where it mates with the shoulder of the spindle. The reason being it might work and the back plate might be able to be used again as enough metal there or if not it would be easier to turn it off in the threaded area with this tool rather than turning the whole six inch plate away.
Photos will follow but once almost through but before risking hitting the spindle , it came off with hand pressure on an adjustable spanner.
What I found ( and had seen befoe once I saw it to remind myself ) was a fault in the threads of the backplate, its got a blow whole in the casting and the threads run through this fault leaving sharp edges that must be the cause I presume.
Anyway its off and the spindle is ok so I just need to make or find a backplate now but have the four jaw chuck until then.
For anyone else with the same problem as I think it was Pete W said with the rifle barrels this method does work so well worth noting .
Cheers Mick
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Glad to hear it didn't damage the spindle thread.....OZ.
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QED
As we used to put after a math problem was solved
Well done and no damage to boot
Stuart
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:thumbup: Excellent news Mick :thumbup:
At least you'll be able to sleep tonight! If the backplate is cast iron (I'd wrongly assumed steel) then perhaps a bit of the material around the casting defect crumbled and jammed. Can you get at the blow hole with a die grinder to relieve around it - sort of blending in, or is it too far into the bore?
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Glad it's off!!
Photos?
Regards, Matthew
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Mick,while we're on the subject of Harrison spindles can I ask how did you determine how much to tighten the adjustment nut behind the timken head bearings. I've had to strip the L6 headstock down to remedy a couple of issues and just wondered how much you tightened your adjusting nut before tightening the second lock nut.
I do have the 2 proper Harrison peg spanners for the job,unlike the butcher who was in there before me with a hammer and punch.......OZ
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Phew! :clap:
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Great :) no damage done or blood spilled :clap:
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Glad you got it off without too many problems. I too would be interested in seeing any photographs.
A blow hole in the casting particularly if there is any loose debris in there would act like a wedge. Not something that would be very obvious.
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SNIP
The Ba##### is off
SNIP
For anyone else with the same problem as I think it was Pete W said with the rifle barrels this method does work so well worth noting .
Cheers Mick
Hi there, Mick,
I'm pleased you've resolved the problem. :D :thumbup: :D :thumbup: :D :thumbup:
Regarding the above quote: not me Guv, I don't do guns!!
I understand what you wrote about having to make more things to do jobs. Still, I think making up a mandrel-gripper gizmo would be time well-spent.
eBay abounds with lathes with gears with missing teeth, usually due to using the back-gear to lock the mandrel. Geared-head lathes aren't immune to such damage, either, leastways if their gears are made of cast iron!
I'd start with a suitable length of large mild steel hexi bar and turn all but about two inches of it down to a snug fit in the rear end of the lathe mandrel. Drill through for a draw-bar and open out the end to form a slow female taper nearly the full diameter of the bar at its open end, then machine two or three longitudinal slits. Make a plug with a threaded axial hole to suit the draw-bar and a male taper to suit the bore of the gizmo's main part. Devise a suitable pin-in-slot to stop the plug rotating in the bore.
It's really a sort of inside-out collet. When it's locked into the rear end of the mandrel bore, the two inches of remaining hex enable gripping with a large spanner to prevent the mandrel from turning. There - it sounds such a good idea, I might even make one myself!
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Good thing. Congrats. Least possible damage.
Pekka
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Hi Lads , I am well impressed at the response and well wishes , I have not had time to post the photos but will tommorow, I owe Dave a few favours as he spent all morning and a few hours yesterday..........good to have mates like that to muck in when times get tricky lolI would do te same but life is so much easier with this sort of arrangement :thumbup:
So I am looking for a six inch backplate I think as probably not worth risking using this one again. Still a puzzle how this chuck and backplate have been used for years by me with no problem before after heavy turning too.
I just saw Pete W's post ......I will look and give proper credit where due lol..........been panicking too much to consentrate :palm:
Cheers Mick
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Thanks should have gone to Willie 'Highpower' from metalworking fun forum who said he had used the same idea of parting off right next to the end of rifle arrels and it had released the stuck threads just before it broke through :clap:
Oz I have not got the answer mate , I was about to run the lathe more then tighten a touch more , I have read that after running 20 mins at top speed the area should just be warm. with all this spindle business my locknut and adjusting nut on the bearings had worked loose though, I do not have the special spanners and my nuts are a bi :clap:t chewed up too. I wil be trying to find out more about bearings and making spanners so will keep you posted.
Cheers Mick
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Mick, I bought the genuine Harrison spanners from the plane iron shop guy for about £5 each.
I'll try and find them again,I'm sure he had some left.....OZ.
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Harrison WR 20 spindle adjusting spanners £6 each, here is the link if your interested.
http://www.ebay.com/itm/Harrison-L5-Adjusting-Wrench-WR20-/360406598334
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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
(http://i1167.photobucket.com/albums/q631/micktoon/Madmodders%202014/MicksL5001.jpg) (http://s1167.photobucket.com/user/micktoon/media/Madmodders%202014/MicksL5001.jpg.html)
Drilling the bar for the incert to fit
(http://i1167.photobucket.com/albums/q631/micktoon/Madmodders%202014/MicksL5002.jpg) (http://s1167.photobucket.com/user/micktoon/media/Madmodders%202014/MicksL5002.jpg.html)
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.
(http://i1167.photobucket.com/albums/q631/micktoon/Madmodders%202014/MicksL5003.jpg) (http://s1167.photobucket.com/user/micktoon/media/Madmodders%202014/MicksL5003.jpg.html)
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
(http://i1167.photobucket.com/albums/q631/micktoon/Madmodders%202014/MicksL5006.jpg) (http://s1167.photobucket.com/user/micktoon/media/Madmodders%202014/MicksL5006.jpg.html)
This is the new tool in the holder lined up for action
(http://i1167.photobucket.com/albums/q631/micktoon/Madmodders%202014/MicksL5007.jpg) (http://s1167.photobucket.com/user/micktoon/media/Madmodders%202014/MicksL5007.jpg.html)
Note the DTI this was to gauge how far the tool advanced to make sure it did not mark the spindle
(http://i1167.photobucket.com/albums/q631/micktoon/Madmodders%202014/MicksL5008.jpg) (http://s1167.photobucket.com/user/micktoon/media/Madmodders%202014/MicksL5008.jpg.html)
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
(http://i1167.photobucket.com/albums/q631/micktoon/Madmodders%202014/MicksL5009.jpg) (http://s1167.photobucket.com/user/micktoon/media/Madmodders%202014/MicksL5009.jpg.html)
This is the backplate after its surgery, just as planned , the spindle not touched but the stress locking the thread releaved so free
(http://i1167.photobucket.com/albums/q631/micktoon/Madmodders%202014/MicksL5010.jpg) (http://s1167.photobucket.com/user/micktoon/media/Madmodders%202014/MicksL5010.jpg.html)
The spindle survived the ordeal
(http://i1167.photobucket.com/albums/q631/micktoon/Madmodders%202014/MicksL5011.jpg) (http://s1167.photobucket.com/user/micktoon/media/Madmodders%202014/MicksL5011.jpg.html)
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.
(http://i1167.photobucket.com/albums/q631/micktoon/Madmodders%202014/MicksL5012.jpg) (http://s1167.photobucket.com/user/micktoon/media/Madmodders%202014/MicksL5012.jpg.html)
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
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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..........
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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
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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.
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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
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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 :scratch:
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Can I retract my earlier opinion? :lol:
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.
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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
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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
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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.
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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
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I cannot help to believe that any kind of epoxy on the threads MIGHT come loose and make another similar problem when least wanted.
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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.
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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.
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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
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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.
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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
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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
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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.
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Hi Lads, well this topic has certainly got some banter going anyway :thumbup: 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 :palm:. 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
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Tony at lathes.co.uk has backplates on stock for £65 .
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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
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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.
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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.
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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
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Some Harrison chucks and back plates on Homeworkshop at the moment:
Homeworkshop.org.uk