How do I undo this ?

[gerry maddenParticipant @gerrymadden53711]

I need to release a feed-screw shaft so that I can remove the worm-wheel gearbox from my J&S grinder. The shaft is held in end by two ‘hook-spanner’ type nuts as you see in the picture below.

My problem is that only one of the nuts partially protrudes above the face of the casting, so hook-spanners cannot be the solution for unscrewing them. What ‘I think’ I need is a pair of coaxial castellated box spanners !  Are such things made ? Probably not!

I have tried to unscrew the lower and smaller of the two nuts using flat-ended pin punch and hammer but its doing damage and not moving anything. Its difficult to hold the screw shaft.

Can anyone suggest a solution?….or a tool ? I would prefer to buy rather than make, as time is of the essence and I have plenty of other tasks to keep me going while it arrives.

Gerry

 

[JasonBModerator @jasonb]

Find a bit of tube and cut some castellations into the end. Or cut from plate and bend to replicate the ER collet nut spanners for the large one and standard hook spanner on the other

[JasonB]

On JasonB Said:

Find a bit of tube and cut some castellations into the end. […]

A selection of old sockets from the flea market is a very useful ‘make-from’ source on such occasions.

MichaelG.

[DC31kParticipant @dc31k]

The sockets do exist to buy. “Axial lock nut socket” is today’s Enigma key.

https://www.bearingsrus.co.uk/skf-tools/skf-spanners-sockets/tmfs0-skf

(complete SKF tooling range catalogue available on same page).

You would need to confirm dimensions – I have no idea if that style of nut is available in both imperial and metric versions.

A bush way is to grind the jaws of a pair of mole grips to the correct width, clamp them on and use a bar through their body to turn them.

[JasonBModerator @jasonb]

The problem with sockets is you may be able to hold the large one but then can’t get at the smaller top one. At least with a holemade one you can chop it about to get access. Or simply have one tubular one inside a shart larger dia one.

Or just buy these if there is room for them

[MichaelRParticipant @michaelr]

If you prefer to buy a tool try this site Link https://impactsocket.co.uk/product/axial-nut-socket-km/ you may find what you require all sizes listed

MichaelR

[Clive FosterParticipant @clivefoster55965]

Surprisingly quick to cut a concentric pair of box spanner style ones from suitable tube if you have mill and rotary table to do the cutting along with a welder to stick handles on.

Way back in a similar situation I spent significantly longer trying “a number of things” and generally trying to be clever than it took to make the proper things.

As a result of this and many similar incidents my (0fficial) rule is to spend no more than five minutes on improvisation before rolling up sleeves to make an adequate version of the real tool. A rule regrettably observed more in breach than following, almost invariably to my distress.

Clive

[noel shelleyParticipant @noelshelley55608]

Take a socket of suitable size and cut down to fit the cutouts. A cutting disc on a 4.5″ grinder makes this an easy task. The socket will be tough so will take a good loading – should work. Noel

[Robert Atkinson 2Participant @robertatkinson2]

+1 for making out of a socket or piece of tube. It is particuarly easy if you make it with two lugs rather than 4. A short piece of tube held in grips can hold the large nut while the small one is loosened.

I’ve seen special tools for similar jet engine and other aerospace fastners made from sockets. When making something like this a socket is a low cost source of forged high quality steel and as a bonus has the square drive ready made Mind you from the cost you would think they were made from gold not Facom or Snap-on parts.

[MikeKParticipant @mikek40713]

I agree with grinding the end of a socket.  I’ve done it for an automotive application.  An angle grinder makes short work of it.  I even made one from bar stock, when I didn’t want to wait for the tool to arrive for my bike.

[gerry maddenParticipant @gerrymadden53711]

Thanks all for your thoughts and ideas. Sometimes one just needs a bit of encouragement to do the sensible thing.

Not finding anything on the web with anything like suitable dimensions, I machined up an castellated alloy ring (for the big nut) and pressed this into a hole bored piece of scrap 1/2inch thick plate. I made it about 40 microns (a thou and a half) interference to ensure it didn’t slip. That was probably a bit much as it proved quite difficult to press in. It required about about 5 tons…I suspect that was less to do with the interference and more to do with it ‘cold welding’ itself on the way in.

I then machined a surplus 1/2″ drive socket to fit coaxially in the alloy part, to mesh with the small nut. To ensure I could use two hands on the socket ratchet handle, I put two holes in the alloy plate so this could be held positively on the casting using studs and nuts. This would also ensure its castellations would stay in positive engagement.

So best part of a day in the making…. but would it work ? Quite honestly I expected something to go wrong, as these things always end up being a development project, but for a change it didn’t. But goodness me, was that small nut tight ! I was convinced I would strip the teeth off the alloy ring, but somehow got away with it this time. Within 30 seconds the job was complete. The shaft was released and this allowed me to take out the gearbox. Its all down hill from here 🙂

Gerry

[Howard LewisParticipant @howardlewis46836]

Good to read that you have succeeded.

Thanks for the feedback

Howard

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