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Mag chuck dismantling

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gerry madden23/10/2021 16:54:20
250 forum posts
131 photos

Afternoon chaps, just trying to dismantle my mag chuck as the handle is much stiffer than I think it ought to be.

Does any one know how the handle is retained on the shaft ? It's not a roll pin or a screw, at least that I can make out, in fact it looks more like a rivet. What I do know is that both ends are a bit of a mess suggesting I'm not the first to try to remove it. It presently looks like this:-



Also, in terms of the separation of the two halves of the chuck itself I'm struggling here too. I have removed 11 long countersunk screws from the base and I can see that there are four locating dowels which must be keeping the two main sections together as seen below.


However, quite a lot of hammering on the overhanging ends of the top plate wont budge it off these dowels. I'm thinking of using a press to force a wedge between the upper an lower plates but thought I better check with the experts on here before getting too aggressive in case I've missed something


Brian Wood23/10/2021 17:36:38
2549 forum posts
39 photos


You are either being very brave or something less flattering!

Eclipse mark these chucks as having no user servicable parts inside and probably for very good reason. I suspect that if you can separate the two haves, getting it back together again will be a real nightmare without appropriate jibs etc that are available at the factory.

Before you go any further with the job, I assume you have given the operating shaft a good soaking in easing oil, and if not I would try that with hot air warming to get it to penetrate.



Dave Halford23/10/2021 18:08:32
2004 forum posts
23 photos

The magnets are said to loose their magnetism pretty quickly.

They are oil filled. follow the link


And here

Edited By Dave Halford on 23/10/2021 18:15:16

Baz23/10/2021 18:23:02
705 forum posts
2 photos

I took my Eclipse 10 by 5 mag chuck apart many years ago because the on off handle was very stiff. The handle on mine was held in by a taper pin and a good wallop got it out. Undo all the screws in the base and it should come apart quite easily, there are three pieces, top and bottom plates and an ally casting for the middle bit. Mine was full of crud, it had been used with coolant and some had got inside and rusted everything. A good wash out and reassembled the same way it came apart and jobs a good un. Would be worth just kissing the top over just to make sure everything is dead true, I was always taught to grind the top of the chuck with the magnets on, others say with them off, no doubt someone will tell me what is correct and why.

Martin Kyte23/10/2021 19:10:10
2721 forum posts
48 photos

If you suppose the chuck is going to distort a little when the magnets are on then I guess you would want to grind with them on. If you do grind with them on you don't get rid of the grinding dust so I suppose you pays your money and takes your pick.

regards Martin

gerry madden23/10/2021 19:31:22
250 forum posts
131 photos

Brian, its probably the latter. My wife tells me that all the time I'm pretty sure its not just the shaft that's seizing up. There something pretty foul-smelling inside this contraption which I found when removing the screws. Baz describes it as 'crud'. I'm not sure that's quite how I would describe mine! I think a large animal has got inside and died.

Dave - thanks for the links. Very useful info. I must remember to do a bit more searching on here before posting As regards losing magnetism there seems to be some debate about that on the internet. But if I do, I'll just have to find out for myself how limiting that is for my tasks. I might be able to live with it. If not then I'll buy a new chuck.

Baz - thanks for your experience. I'll give that a go on the handle. After that I'm not sure mine is going to come apart as easily as yours did. But let me play a bit more and see what happens.


Edited By gerry madden on 23/10/2021 19:32:57

Brian Wood23/10/2021 20:36:47
2549 forum posts
39 photos


The handle on mine is a lift off key, square form male into a socket if I remember correctly without going out to check it. The handle itself is die cast carburettor metal which will not take severe torque on the small area of the square key. I have used total immersion methods in kerosene to free off seized or partially seized mechanisms, leave it overnight to give it a chance to creep inside.


PS My wife is frequently of the same opinion but we still get along well together!

Baz23/10/2021 21:31:57
705 forum posts
2 photos

Gerry, don’t bother removing the handle, it should come away with the centre section of the chuck. I have taken a few of these apart in my time and some can be reluctant to come apart, one chuck needed persuading with a four inch bricklayers bolster applied under the top plate to lift it up, it had to come apart, it was seized solid, others have fallen apart as soon as the screws came out.

peak423/10/2021 21:43:34
1671 forum posts
175 photos

For an Eclipse permanent magnet chuck, the instructions from the makers, say that the handle should be "Off" when re-grinding.
Not that other makers may have different guidelines, particularly for electric chucks.


peak423/10/2021 22:33:37
1671 forum posts
175 photos

p.s. I'd forgotten, the manual is available on this site


Baz24/10/2021 09:36:04
705 forum posts
2 photos

Thanks Bill, I will in future grind it with magnet off. Never seen any manual for the chucks before.

gerry madden21/11/2021 12:53:48
250 forum posts
131 photos

As Mark Bolan said 'all I want is easy action' and that's what I now have on my mag chuck. It was a bit of a struggle to get the beast apart. I had to clamp the base-plate to my bench and get a crow-bar on the top-plate to separate it, but once apart it was really just a clean-up operation. A wire brushing and a dunk or two on a bucket of white spirit was mainly all that was required.

There were a couple of points worth mentioning for anyone else attempting this often frowned-upon task. The first one is that I found the epoxy fillings between the poles were protruding quite significantly above the inside surface for the top plate. Suspecting that these could be part of the cause of the operational stiffness I cut them back with a blade until they were absolutely flush. The chuck couldn't have been made like this so my guess is that the epoxy has swelled a little over time from oil absorption. In the pic below the 'white bits' indicate where the epoxy was cut back. This pic by the way was taken in the almost-finished condition. There was much more protrusion beforehand.


The second point was that the aluminium frame came with only one oil lubrication hole in it. This didn't make any sense to me as its just as important to let the rubbish out as put new oil in. So I drilled and tapped 3 additional M10 grub-screw holes so that there were two on each side.. I can now add oil and drain simultaneously whilst operating the chuck.


I have to say that this was a job well worth doing and I'm astounded at the improvement its made. I can operate the on/off handle easily with one hand now where as previously I needed two arms and an extension tube. Of course some might say that this improvement is because I have lost all the magnetism. I suppose I might have lost some, I can't actually prove it either way, but I honestly can't tell that the chuck is any different to before. If I put a rough cast iron plate 3" x 5" on the chuck I simply cannot move it by hand and that's good enough for me.


Edited By gerry madden on 21/11/2021 12:56:34

Baz21/11/2021 13:42:35
705 forum posts
2 photos

Glad you have got it working and thanks for letting us know, like the idea of extra oil holes.

bernard towers22/11/2021 00:35:36
568 forum posts
109 photos

My round eclipse chuck was stiff to operate when I bought it (secondhand) but had an oil filler hole , plug removed and nothing came out so in with some hyd oil and now is silky smooth.

John Olsen22/11/2021 05:02:21
1240 forum posts
94 photos
1 articles

Being apart for long enough to clean the chuck out is unlikely to have any noticeable effect on the magnets. It will depend a bit on how old they are, the older materials were not as good.. If you need to have a chuck apart for a long time, rig up some sort of keeper for the magnets, it just needs to be iron or steel that provides a path from one pole to the other. The Alnico material used by Eclipse is pretty good, I'm not sure when they started using it by I think maybe some time after the war. Later materials are even better.


Michael Gilligan22/11/2021 07:53:54
20057 forum posts
1040 photos

Good result, Gerry yes

Thanks for sharing the experience.


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