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stuck chuck again

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Philip Burley05/06/2020 11:21:57
198 forum posts
1 photos

I cant get the chuck off my Suoer 7 , The pin at the rear wont hold the shaft , I have tried all the usual methods . Thinking about un bolting the chuck and turning the back plate away , or removing the spindle and hopefully griping more tightly . . Others must have had the same problem Or simply leaving it on and using my other lathe if I need a 4 jaw job


Tony Pratt 105/06/2020 11:46:24
1698 forum posts
8 photos

Ok I had a super 7 for 50 years but never had a completely stuck chuck, I would suggest either putting a chuck key in the chuck & whacking it down with a hammer or putting a hexagon bar in the chuck applying a ring spanner & hitting it with again a hammer, all the time protecting the lathe bits & pieces, I also wouldn't put it in back gear to do this as something may break, quite often a sharp tap will do the trick, careful does it.

PS, missed the bit about the pin not holding, first find out why not, I always used that to hold the spindle.


Edited By Tony Pratt 1 on 05/06/2020 11:47:39

Sandgrounder05/06/2020 11:47:34
229 forum posts
6 photos

My apologies if you know this already but the pin that won't hold the shaft, is it in the right hole? On mine to lock the headstock shaft I push the pin in and turn the chuck until it locks, but there are 2 holes diametrically opposite, one has the oiling nipple and the pin won't fully engage and slides out when the chuck is turned and the other the pin fully enters, I can't see how the latter won't hold, it may break something but shouldn't slip.

Edited By Sandgrounder on 05/06/2020 11:50:40

peak405/06/2020 12:26:52
1496 forum posts
162 photos

Try the following, bind the two halves of the headstock V belt together to lock the spindle, after making sure you have normal drive, rather than backgear engaged.
If it's a 3 jaw tighten a large allen key in the chuck with the long side extending towards you and smack the nearest end of it with a hammer sharply.
Alternatively, if no large allen keys, a large diameter piece of hex bar and suitable spanner to fit.
A similar arrangement can be set up for a 4 jaw, or use a length of square bar across the face of the chuck and held by all 4 jaws.


Edited By peak4 on 05/06/2020 12:27:57

Baz05/06/2020 12:31:35
585 forum posts
2 photos

Don’t remove a chuck by putting the chuck key in the chuck and hitting it, you will break the square out of the pinion. Use a piece of square bar, I use a piece of 1/2 square about a foot long, place it between the chuck jaws and a good push should remove the chuck. Engage the pin at rear of headstock as Sandgrounder says, do not engage back gear, you will probably strip some teeth off.

Peter Sansom05/06/2020 12:32:48
96 forum posts
2 photos

Remive the locking pin for the chuck. then you can have a look through the pin hole. Use a piece of wire, welding rod etc, to feel the hole in the pulley. You should be able to see how far the wire goes in the hole.

If tehre is nothing jammed in the pullley hole use a bolt that is smaller than the locking pin to lock the pulley.

Never use a chuck key to remove the chuck and NEVER hit the chuck key. I use a strap wrench which will not damage the chuck. The strap wrench I have uses 25mm webbing. I had to put a longer lenght of webbing in to go around the 6" chuck


Tony Pratt 105/06/2020 12:48:29
1698 forum posts
8 photos

Plenty of advice on here now, let us know how it goessmiley


Grindstone Cowboy05/06/2020 13:16:49
711 forum posts
58 photos

Just one thing that seems to have been missed - put a piece of wood on the bed to protect it when the Allen key you are hitting to loosen the chuck spins round and hits the front shear. Don't ask me how I know this...


Philip Burley05/06/2020 13:42:33
198 forum posts
1 photos

I have tried all those methods , except checking if I am using the right hole for the locking pin . not used back gear , not hit the chuck key

I will check that this afternoon


Mike Henderson 105/06/2020 13:58:03
28 forum posts

I had a Super 7 for a long time and once had a very stuck chuck. The locking pin wouldn't hold for me either. IIRC the pin actually locks the pulley. the 'flipover ' lever locks the pulley gear to the bullwheel which is keyed to the mandrel.

The weak point was that the pulley was a force fit onto the bronze (?) pinion. Trying to remove the chuck caused slip of the force fit.


Final solution was lock with the pin AND knock a wooden wedge between the bullwheel and the headstock casting - that's a firm knock, not flog it into place with a lump hammer. Then a square bar in the chuck, a suitable spanner . a couple of firm taps on the spanner to set the wedge and a good clout.

All done with extreme trepidation.

After that, I never left the chuck fully screwed on the mandrel at the end of a workshop session - and always remembered not to start the lathe with the chuck slack. I should also add that the pulley/pinion fit never slipped in use.

Incidentally, while I have used quite a few lathes over the years, the Super7/ML7-R is the only one I've come across to have a mandrel lock. Are there others?

Keep safe


Edited By Mike Henderson 1 on 05/06/2020 14:00:08

Hopper05/06/2020 14:03:04
5505 forum posts
137 photos mentions the method of placing a block of wood on the rear bed way and starting the lathe up in reverse in lowest back gear. When the chuck jaw hits the block of wood, chuck should come loose. May take several attempts, it says.

More details and some other suggestions here **LINK**

Philip Burley05/06/2020 14:27:49
198 forum posts
1 photos

YES YES YES , Done it , I must have been using the wrong hole for the locking pin , 5/8 square bar i the chuck and a copper hammer and it came first time . I cant imagine why it wouldn't move before ,

I have heard that a gasket on the mandrel before screwing the chuck on will prevent it happening again , is that right ? I have been doing quite a bit of heavy machining , but only on aluminium .

Thanks again guys for the help , I was seriously thinking of dismantling the spindle , or machining the back plate away


Brian Wood05/06/2020 14:54:48
2452 forum posts
37 photos

Hello Philip,

Avoid the gasket, it could well throw the chuck alignment out. Those faces need to be in intimate contact to ensure true running, the gasket will introduce error from variable thickness in the rolling if it is present

Regards Brian

PS. You would never have been able to grip the bare spindle well enough without causing damage to it to overcome the tight fit. On a different lathe [ Smart and Brown Sable] I was forced to try that method on a hardening spindle using shaped wooden blocks as a pair of vice jaws. It just laughed at those and I had to turn off the backplate in the end 

Edited By Brian Wood on 05/06/2020 15:00:15

Brian H05/06/2020 15:05:56
2230 forum posts
113 photos

Incidentally, while I have used quite a few lathes over the years, the Super7/ML7-R is the only one I've come across to have a mandrel lock. Are there others?

Keep safe


Hello Mike, the Boxford lathe has a spindle lock. It's a round button on the front of the headstock that is pushed in and the the spindle is rotated until it engages.


old mart05/06/2020 15:42:14
3347 forum posts
208 photos

I use a sturdy strap wrench to unscrew the Smart & Brown 1 3/4 x 8 spindle thread, it is much safer than chuck keys and hammers. The Pratt 6" lightweight four jaw independent jaw screws are particularly easy to split using this method to unscrew the chuck. The threads on both parts should be dead clean and be lightly oiled before mounting the chuck or plate.

Howard Lewis05/06/2020 18:35:04
5320 forum posts
13 photos

Another possible way to free a stuck chuck is to clamp a piece of sturdy (18 mm + ) hexagon bar, firmly in the chuck, and then apply a well fitting ring spanner, or a socket and power bar.

With the belts tight (to utilise the inertia of the motor) give the far end of the spanner a hard blow with a copper mallet, following through.

After two or three such blows, most stuck chucks come free.

(My lathe has a 8 " four jaw chuck, so no lightweight. A 8mm hole drilled into the rim, and a hefty bar with short length of 8mm silver steel, inserted into the hole, when hit in this way, frees the chuck, every time )


AdrianR05/06/2020 18:49:02
540 forum posts
36 photos

I have the same lathe as Howard, I keep a 30mm sq x 300mm length of beach in my drip tray. Tighten it across the jaws, grab both sides of the v belt in my left hand and wallop the wood with a rubber mallet.

As Howard said, the trick is the follow through.

If your chuck is regularly getting stuck it sounds like something is wrong. Maybe a very light stoning of the register faces to see if there is a burr. Or check the threads for roughness or imbedded swarf. Then of course there is the debate to oil or not oil. I wipe it dry each time i fit in the belief oil helps it tighten more than it helps it loosen.


Howard Lewis05/06/2020 19:01:44
5320 forum posts
13 photos

As Adrian says, the threads and registers should be checked to ensure that they are clean, before fitting.

An old tooth brush can be a handy way for doing this.


Hopper05/06/2020 23:56:44
5505 forum posts
137 photos

Always put some copper anti-seize grease on the threads and spindle before screwing the chuck on. Makes a big difference.

Edited By Hopper on 05/06/2020 23:57:31

Philip Burley06/06/2020 07:42:13
198 forum posts
1 photos

The copper grease sounds like a sensible idea I wil get some .. have to be on line though , till local shops reopen


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