Jacobs Chuck

Hi all,

Along with a few tools for my newly aquired Naerok mill / drill, it came with a good condition Jacobs Chuck 36 (3/16 to 3/4 inch or 5 to 20 mm - 3 taper).

It nips up OK, but if you apply more pressure the outside body turns with no more torque being applied to the tool or drill.

I had a good look but can see no way in for a clean and grease - is it possible to take it apart and if so how?

Thanks for any suggestions - Paul.

Paul

they are easy to take to bits but you need a press or large vice and spacers to push the body ring off..having said that i have one that does what you describe and i cant see anything wrong with it inside..

Fate decided to intervene to prevent you using milling cutters in a drill chuck.

Thanks Ian - which way does the body ring push off?

Pete - the cutting tool was only used to prove to myself that there is an issue with the chuck.

Regards - Paul.

The outer ring is a press fit on the screw ring inside. Seems like yours is slipping. Check the outer ring carefully for any hair-line cracks especially in the bottom corner of the grooves.

I would also tend to suspect a cracked outer ring, the interferance fit should be enough to prevent the tightening forces causing slippage.

Have a look at the web site as it tells you how to repair the chucks.

http://www.jacobschuck.com/tech-support/

David

Fair enough, it just looked like the shank of the cutter was shiny then marred exactly where the chuck Jaws are, like it had been slipping, good to know you know better.

If you have access to previous copies of MEW, there have been at least two articles on stripping, cleaning and reassembling drill chucks.

Howard

The ring pushes off over the printing, back off the jaws underflush before pressing. There are marks on the jaws to help when refitting them in the correct order like the jaws in a scroll chuck.

Edited By old mart on 01/02/2021 18:10:09

Lots of info on the web just search “Jacobs Chuck disassembly” I have no t looked at any but lots of videos etc etc.

Never tried this but regarding the slippage of the outer ring maybe reassembly with Loctite May solve the problem? Any thoughts anyone !

John

And run a file or stone around the snout to knock off any high spots before pushing it into the ring. Sometimes there are burrs there, especially around the three keyholes.

When you disassemble it, the nut will be in two pieces and look as if it is broken. It is made that way: in one piece with weak points and then split to facilitate assembly.

If you cannot find any visible cracks, and do not want to proceed straight to disassembly, make up a clamping collar to go around the ring, squeeze it up tight and see if the wheelspin disappears.

Possibly, you could repair it by drilling and tapping the outer ring for grubscrews. Rather than exerting pressure on the nut, which might not be a good idea, you might have to grind a dimple in the nut just so the grubscrew stops relative rotation of the two parts.

From David George's advice. Here is the instructions.

Steve

To repair a keyed chuck

All - thanks for all the information.

There are no cracks in the outer ring.

I pushed the outer ring off in my vice, a bit rusty inside but not too bad.

Washed it all out and removed the rust, then greased it all and re-assembled, ensuring that the interferance surfaces are clean and dry.

Just the same, slips when pressure applied.

I like DC31k idea above of grub screws to stop any slip between the outer ring and the split nut. You could not just do them up as the pressure on the split nut would lock the jaws. Rather locktight them in place in a dimple in the split nut - one each side. 

Thanks - Paul.

Edited By Paul Smith 39 on 01/02/2021 20:26:23

Could you see the signs of the slipping? I don't think Loctite would work, it requires enough clearance to glue the joint, and a light push fit would just push the Loctite out of the way. The grubscrew approach may be your only solution. I don't know how thick the wall of the outer sleeve is, or whether the parts would be hardened.

I would be inclined to try a somewhat nasty fudge to restore the necessary interference between the split ring and the outer ring. Find some 2 thou (or thereby) brass shim and make packing pieces to insert in the splits. Brass would be more able to conform to the irregular split line and bed to a uniform spacing, and if necessary, anneal it.

Putting 2 thou in both splits would result in circa 1.3 thou increase in diameter, so quite a tight interference. You would probably need to glue the slivers of shim in place for assembly, but once pressed together it would be solid.

While I hate to throw out anything repairable, a Jacobs 36 chuck appears to cost between 55 and 75 quid from a quick internet search, so before you go mad, what do you cost your time out at? - if you spend several hours and don't get a 100% as new result, was it worth it?

Edited By Nick Clarke 3 on 02/02/2021 22:29:32

The current Jacobs chucks are made in China and are not reconed to be of the same standard as the UK, or USA products. I have been lucky and have picked up a NOS 1/2" British made one. The best running chuck we have at the museum is an R8 integral shank 1/2" Cutwell keyless one. You may be lucky buying a cheap chuck, they all seem to vary in runout, even the expensive ones. My favourites are the Kawasaki keyless, they will run in reverse if needed.

Edited By old mart on 03/02/2021 12:16:17

Thanks alll for the further suggestions. I ended up at G&M tools Ashington and have bought a very good condition Jacobs 36 on a MT3, plus a Jacobs keyless chuck also on MT3. I've had to buy a R8 adapter to take the MT3 - cheap on eBay.

So - all resolved now. Thanks - Paul.