Stuck chuck

[Simon CollierParticipant @simoncollier74340]

I am new to screw on chucks as my only lathe until recently has cam lock chucks. I cannot get the 4 jaw chuck off a Hercus 9" lathe, even though I only put it on a week ago, and only then to see how it looked! I have applied as much leverage against the back gears as I dare and I can see no way of locking or spraging the spindle. I have searched this forum, and Google, and there are several ideas, most of which I don't like. I don't want to damage the chuck or break gear teeth, obviously.

[Simon CollierParticipant @simoncollier74340]

[hthParticipant @hth]

Hi

You are in Australia ?

This might help

http://www.model-engineer.co.uk/forums/postings.asp?th=118159

[not done it yetParticipant @notdoneityet]

I use all manner of methods to remove the chuck. But if it is truly stuck and you will break off bull gear teeth, or worse, here is the idiot proof method of preventing the spindle from turning while applying considerable shock-force to the chuck.

Not the cheap

est of cures and needs some work, plus some imagination, possibly.

Open chuck jaws wide. Insert a tapered threaded arbor (of whatever taper your spindle accepts as a centre), tighten it in position with a drawbar through the spindle, attach some form of lever, either at the drawbar end (if it does not unscrew while applying chuck removal force) or at the chuck end. Job done as best possible, I would suggest.

 

My lathe had been laying outside for several years, yet did not need that much force to remove the chuck. The ultimate method would be to remove the chuck from the back plate and carefully destroy the back plate by turning it, making sure you do not damage the threaded nose on the spindle.

Edited By not done it yet on 20/06/2016 09:54:41

[Simon CollierParticipant @simoncollier74340]

The 3 jaw I took off had been on it for years and it came off easily. The stuck 4 jaw has no backplate. It is a thin bodied, directly threaded type in beautiful condition, probably unused. Yes I'm in Sydney, and thanks HTH, I have just read that post. I'll try the inertia method with a large shifter on a bit of square bar and failing that, I might make an expanding collet to go in the plain bore of the rear of the spindle bore, rather than risk damaging the spindle 3M taper.

[Brian WoodParticipant @brianwood45127]

Simon,

I hope you haven't screwed on an incompatible chuck, it is odd to have a grab after such a short time. The TPI of the nose thread for South Bend lathes and all it's clones [ Hercus, Boxford etc] is the same, but the thread pitch angle for the US lathe is 60 degrees.

Boxford I know is 55 degree Whitworth, but I am not sure about Hercus. They anglicised the gearbox with gearing for UK pipe thread pitches instead of the US 23 tpi pitch, and that process might have included the nose thread on the spindle as well

If John Ockleshaw in Oz reads this, he can advise you properly, he owns a Hercus 9" lathe

Regards Brian

[old AlParticipant @oldal]

Go find all of your 4 jaw jobs and do them first. getting the machine warm in the process, might take 3-4 hours of doing stuff. Then try and undo the thread. Dont do it the quick way and put a blowlanp on it.

[BazyleParticipant @bazyle]

I don't think you want to warm up the bearings first as that would expand the mandrel more than the chuck. An MT3 icicle might be better.

[Simon CollierParticipant @simoncollier74340]

Well I tried the shock/inertia method, with square bar in the jaws, and a large spanner on the bar, then hit with hammer, in low gear. Nothing. I am getting really worried now. I only screwed it on very recently. It came with the lathe so I don't see how it could be incompatible. It screwed on easily. Who invented screwed chucks anyway! What a stupid idea. I am about to go to bed with this problem swirling around in my dreams, if I can get to sleep that is.

Bazyle, if a 3 MT icicle is not as describled by "not done it yet" above, what is it please?

[HopperParticipant @hopper]

Just how much pressure have you put on the chuck while using the back gear to lock the spindle?

Have you tried a two-foot-six long piece of wood passed between the open jaws of the chuck and giving it a few good yanks?

You have to remember the back gear transmits the power from a half horse motor geared down considerably to deliver torque well in excess of what your arm will provide. (Try grabbing a spinning chuck and stopping it. – er no dont actually try it but imagine it)

Using a length of wood provides a bit of spring so is a little easier on the back gear than pounding on steel bars with hammers etc. Works for me.

Once off, lube up the chuck threads and the spindle's with Never Seez copper slip etc and you shold not have the problem again, provided chuck is the correct thread etc.

[BazyleParticipant @bazyle]

Icicle is the opposite of warming up the bearings. 3MT to fit in spindle nose and cool it as in Oz I imagine it is fairly warm at the moment. Obviously don't cool down a steel MT3 and put it in the hole as it will expand and jam.

Not sure which previous threads you have read but one of the ways of relieving the strain on the bull wheel teeth is to make a curved length of aluminium with filed teeth on the inside to fit the wheel. This then spreads the force over multiple teeth and being Al it gives to make up for your initial roughly filed teeth.

[peak4Participant @peak4]

Posted by Bazyle on 20/06/2016 14:08:42:

Not sure which previous threads you have read but one of the ways of relieving the strain on the bull wheel teeth is to make a curved length of aluminium with filed teeth on the inside to fit the wheel. This then spreads the force over multiple teeth and being Al it gives to make up for your initial roughly filed teeth.

I've never tried it myself, but I guess, depending on clearance, one could put a strap wrench round the bull wheel.

This might spread the load out a bit.

Personally, I've gone down the route of engaging the clutch, and spinning the belt by hand. If a suitable length of wood is stood on end on the lathe bed, a jaw will catch it and the inertia of the gear train and motor has always freed off a stuck Myford chuck; just remember to do it in the correct direction.

[JssParticipant @jss]

How about warming the chuck, with a hot air gun, until it's nearly too hot to touch and then squirting one of those freeze sprays, that DIY stores sell for freezing water pipes, into the spindle morse taper? You may have to blow warm air in afterwards to take away any condensation that forms inside the spindle.

John.

[mark smith 20Participant @marksmith20]

When you put the chuck on did it screw on easily all the way with the same pressure. My South bend came with good chucks but the backplates were probably Boxford. One of them screwed on with little pressure and then goes very stiff and locks around 1/4" from the spindle register . Luckily i noticed something was wrong before i tried to put more pressure on the chuck to get it further on. The nose threads suffered no damage.

Seemed strange that the retired engineer i bought the lathe and tooling from was using an improperly fitting backplate for years .

There are many sellers particularly on ebay selling backplates claiming to fit Southbends and Boxfords, other clones etc.. but they just don`t fit as mentioned above ,wrong thread angle.

[mark smith 20Participant @marksmith20]

When you put the chuck on did it screw on easily all the way with the same pressure. My South bend came with good chucks but the backplates were probably Boxford. One of them screwed on with little pressure and then goes very stiff and locks around 1/4" from the spindle register . Luckily i noticed something was wrong before i tried to put more pressure on the chuck to get it further on. The nose threads suffered no damage.

Seemed strange that the retired engineer i bought the lathe and tooling from, was using an improperly fitting backplates for years on all the chucks .

There are many sellers particularly on ebay selling backplates claiming to fit Southbends and Boxfords, other clones etc.. but they just don`t fit as mentioned above ,wrong thread angle.

[nigel jones 5Participant @nigeljones5]

So its not just me then! My 3 jaw comes off easy but the 4 jaw is a complete nightmare to break free. Both have very free running threads and I keep them lubricated!

[Neil WyattModerator @neilwyatt]

I have limited experience of screw on chucks, but might a smidge of copper-ease be a sensible precaution in future?

Neil

[not done it yetParticipant @notdoneityet]

As above, I have a screw on chuck. Yes, I would prefer an alternative but it is what it is. I believe that most back gear breakages occur because the gear train is locked by engaging both back and forward gears together (yes, I am guilty of doing this to easily remove my chuck – but I don't over do the force!). My spindle centre is MT4 and I don't think I could damage the contact surfaces with any amount of reasonable force applied to the chuck. An MT3 should not suffer, either, if the drawbar is tightened sufficiently.

Another problem is fitting at different temperatures – cold and hot do not mix when making tight connections as they will either loosen or tighten. Many a morse taper has been made very difficult to remove, by expansion after fitting tight. Slightly wrong threads may make things even more troublesome.

I always use plenty of oil when putting on the chuck. I reckon that the excess, when squeezed out, is likely to carry with it any unwanted particles which may cause problems (just a precaution, not an excuse to spin onto dirty threads!).

This is what was done when fitting mill diaphragm plates in large grinding installations (3000HP?), where the bolts were tightened until the heads sheared off. Grease was used, in that scenario, to carry away any grit that may otherwise have been trapped between the bolt seating surfaces. No going back to tighten after installation!

[HacksawParticipant @hacksaw]

45 years ago , I watched dear old Ken Finch (the metalwork teacher ) , pull a chuck by whopping the chuck key with a mallet …. As a child i saw Dad pull a Black'n Decker chuck off his pistol drill, by whopping the chuck key with a hammer… I'm afraid I thought this was the way to do it .. It never crossed my mind to tighten a bar in the jaws, and give it an American.. Everyday's a school day, I'll not abuse my chuck key again ….!!

[Paul LousickParticipant @paullousick59116]

Also as a child I saw someone hit the chuck key on a B&D drill with a hammer to remove the chuck. A few years ago tried this trick on an expensive cordless drill and smashed the gears. Will be more careful next time.

Paul.

[Martin 100Participant @martin100]

Posted by mark smith 20 on 20/06/2016 18:55:57:

There are many sellers particularly on ebay selling backplates claiming to fit Southbends and Boxfords, other clones etc.. but they just don`t fit as mentioned above ,wrong thread angle.

One of the UK based suppliers did that with their 'Boxford' spindle nose fitting ER chuck.   Complete PITA trying to resolve that one. 

We had a very stuck 3 jaw chuck on a Boxford a long time ago. Probably caused by a bit of swarf as it had been swapped with a 4 jaw numerous times.

In the end, after trying all the usual solutions – breaker bar on a socket extension gripped in the chuck, alternate heat and cold, penetrating fluids of various types, swearing, pleading etc, it was a case of remove the chuck leaving the backplate on the spindle, then apply a hacksaw cutting almost all the way down to the thread and lever the vee apart with a cold chisel while hitting it with an appropriate weight of birmingham screwdriver. It wasn't pretty, the bearings survived without issue but were replaced a few years afterwards, the spindle runs true and the lathe still turns parallel.

The backplate is still sat on a shelf at the back of the garage some 30 years later.

Edited By Martin 100 on 21/06/2016 00:29:15

Edited By Martin 100 on 21/06/2016 00:30:18

[Simon CollierParticipant @simoncollier74340]

It's off! I did sleep badly, but this morning I read the posts first thing, and tried Hopper's method with a bit of wood, 1-1/2 x 1-1/2 soft wood 3 or 4' long. The wood sprung, taking the load, then the chuck just turned. So thanks Hopper and thanks all for your thoughts and ideas. Never seize will be applied!

I checked the spindle thread once the chuck was off. My 8G Whitworth thread gauge was a perfect fit, although it is 55 degrees. The spindle thread is specified as 1-1/2 x 8 USS (obsolete but usual US 60 degrees, I think). I am, therefore quite confused about this. The chucks are UK made, the 4 jaw is Burnerd cat #1548-16080, if that means anything to anybody.

[Enough!Participant @enough]

Posted by Paul Lousick on 20/06/2016 23:27:36:

Also as a child I saw someone hit the chuck key on a B&D drill with a hammer to remove the chuck. A few years ago tried this trick on an expensive cordless drill and smashed the gears. Will be more careful next time.

….. and also remember it's a left-hand thread.

[Simon CollierParticipant @simoncollier74340]

Found a UN thread gauge; it fits better than Whitworth, so definitely 60 degrees on spindle nose.

[Paul LousickParticipant @paullousick59116]

Hi Simon,

I have a 9" Southbend lathe and the Hercus was a copy of the Southbend and should be similar to the one which I own. I am always careful not to over tighten the chuck when I screw it on. Only tighten with firm pressure. Do not spin it on at speed or you have trouble getting it off. Too much force on the back gears will break teeth. Luckily I have not had too much trouble.

The spindle drive gear on my lathe has large lugs at the side for the drive pin. I have not done this but you could place a block between the lug and the lathe bed to stop the spindle turning while undoing the chuck (see photograph).

A better option, instead of a block of steel would be to make a special spanner that would fit into the slot at the side of the gear to stop it turning. Use a large spanner or steel bar to turn the chuck.

Paul.

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