Norton Quick Change Gearbox Removal

I had a jam up on my lathe this afternoon which has caused damage somewhere in the Norton quick change gearbox - it also stripped several teeth off the input gear!

The lathe is a well built German Weiler LZ 280 lathe of uncertain vintage - probably late 1960's very early 1970's. The quick change gearbox has the usual two shaft outlets, a leadscrew for screw threading on top and a splined shaft - posh term for a shaft with a longitudinal keyway - in the bottom for power feeds.

I am trying to remove the gearbox to see what damage has been done and to repair it. The box has been detached from the lathe and the leadscrew is out but it is resisting all attempts to detach the power feed shaft. The manual gives no instruction for removal but states there is a "safety slip-clutch of spring-loaded key-drive design, located in the end bearing of feed shaft at quick change gear box, protection is assured against overload" (lost a little in the translation perhaps!) but the drawing is less than clear and offers little to no guidance to the shaft's removal.

Where the feed shaft disappears into the box there was a circlip which I thought might be holding things back but it's removal has not helped, it doesn't want to come out and prefers to just slide through the apron as I try to pull it clear.

As an extreme measure I suppose I could pull the feed shaft all the way out the apron, but then I fear the mating key might fall out and that would mean the apron would need stripping down, but before I venture down that route:

Has anyone any idea how the feed shaft is removed? There has got to be an easy way - I just don't know it!

All help gratefully received.

Chris

Chris

It sounds like the description of colchesters to removing the feed shaft..there's a spring loaded ball clutch in the shaft..as i remember you loosen an Allen screw and the ball comes out and then the shaft withdraws..any pictures of your set up?

Hi Ian, No pictures as yet, will try some tomorrow - am all cleaned up and in reflective beer supping mode now!

Sounds reasonable your solution, but where would the allen screw be? Not seen one, but that is not to say there isn't one. Will look again in the morning, it should be fairly visible if there is one, I would have thought.

Chris

OK - two photos of the problem:

So, the circlip is off and that's it. the feed shaft is still solid in the box. The little dark dot on the feed collar would suggest a pin through the shaft and it's collar, except that no pin is visible in the collar, it's just a hole down to the shaft (I think). I might try drilling through, just to be sure, it's a 2mm hole.

Pulling the shaft out through the apron is not an option, the feed shaft keyway does not extend to the end of the shaft.

My thought are now, if the feed shaft will not come out, I am thinking of cutting the shaft near the box, under the leadscrew sleeve above. This will free the box so I can get it to the bench. Then I will make a collar to cover the cut and secure it to both sides of the shaft with grub screws into the keyway, when it gets reinstalled Unless anyone can flag up a problem with doing this! Then at least I have a means to remove the box easily in the future, should it be necessary. I don't like the idea of cutting the shaft but I don't see an alternative.

Without any bright ideas on getting the feed shaft out the box I don't know what else to do. Cannot see any allen screws to undo to release the clutch, there appears nothing obvious. More pondering to do!

Chris

Are you sure that the hole isn't a taper pin perhaps with a thread in to extract it...when i enlarge the picture there seems to be slight sight of a ring around the hole..the arrangement in your picture is nothing like the colchester feed shaft clutch

Cutting and making a collar to span the cut would certainly work but it surely should come out easily

The shaft must have been in one piece when it was installed, so, it must come out. ( don't ask me how )

Roy

Ian - Either side of the hole the collar and the shaft are marked with an 'o' which to me are witness marks, which in turn suggests the shaft should come out. The hole is only 2mm diameter and it appears solid a little way down, The same the other side. I can try grinding down a pin punch to fit the hole and see I can punch it through, see if that works

If not I will try drilling through the hole to ensure it's clear and then try pulling the shaft out again.

I agree, it surely should come out easily, the problem is, it doesn't. Story of engineering life really!

Roy - Indeed the shaft was in one piece when it went in, so it must come out. Trouble is, I don't know how it went in - I was hoping someone on here would know how, it must have been seen before.

Chris

**LINK**

Take a look at this, the rebuild shows that the shaft should withdraw from the collar on the rt. hd. side of gearbox

A pin through a cross hole is common practice when joining such shafts to a bored to fit collar. Frequently the pin is made small and / or weak so that it shears when overloaded to protect the drive train. Unfortunately if a plain pin is used it can smear at the shear line between the shaft and the collar instead of breaking cleanly. If this happens things tend to twist a bit and jam up solid with the remains of the pin somewhat out of line with the holes in the collar.

Given the small size of you joining pin I suspect this has indeed sheared at the joint line and smeared across so drilling out won't help. The smeared material takes up clearances and holds in against movement in all directions. Odds are it sheared one side first then the other after bending the pin slightly. The bend makes the smearing effect worse.

Best way to release things is to twist the shaft relative to the collar bringing the pin back into alignment with the hole so it can be driven out. If you can get things moving can be possible to feel the smeared pin moving back into alignment with the holes for driving out. 50/50 chance if the four similar jobs I've done are typical. Anoint with plenty of plus gas or similar releasing stuff, heat, try, re-anoint, wait and have another go type job.

Solid clamp on levers to hold the shaft and collar for mutual twisting will be more secure and less damaging than grips. Ideally alloy on steel as this holds better than steel on steel..

Clive

PS:-  KWIL posted whilst I was typing.  Interesting picture and smeared pin theorry may not apply but that one looks to be slightly different design to yours.

Edited By Clive Foster on 04/07/2017 10:28:35

KWIL - I was just looking at the link you posted and that exact picture. Slightly different arrangement there to mine I think, but there is a suggestion on other pictures on/in the link that at least some part of it unscrews. However on mine there are no flats or knurls to suggest a screw. The shaft MUST withdraw somehow. Are the pegs just temporary locators perhaps? I don't like butchering innocent parts but to unscrew mine I would have to use stilsons or similar to hold one bit whilst I turned another. Thinking out aloud here. Perhaps as it's been in there for so long there is a certain tightness developed? It needs another dose of 'looking at'!

Clive - on the collar and on the shaft are two what I think are witness marks - a little 'o' stamped on each. They are inline with each other which made me think that the shaft hadn't twisted round. However, that is not to say it hasn't moved in or out, or even around. At the moment I haven't been able to move the shaft round relative to the collar, but I will try again - and I have Plus Gas! I hope that the pin hasn't sheared and cause a seizure, that won't help at all, but it would explain the reluctance to move.

Chris

PS - indeed, the picture that KWIL posted does look different to mine, but I suppose the same basic design could have changed or evolved during the production run

Edited By ChrisH on 04/07/2017 10:48:23

Eureka! The feed shaft is out. Holding the collar and turning the shaft did not work but , after noticing the collar would move in and out the box a little I had a sudden inspiration. I tapped the collar inwards whilst holding the shaft and collar out and it moved relative to the shaft. Pulling the shaft and collar out then tapping the collar in, and repeating and repeating worked, the shaft slid out. And Clive, you were quite correct, there was a pin sheared in the shaft and the shaft had at some time moved out about 3mm. Pin is now removed, new 2mm dia pin to find, and I can now sort the gear box out.

Just for the record, don't know what the exact internal set up is still, but there are two collars - you can see them in my pictures. When the inner collar is moved to the right it engages with the outer collar and both rotate together. When the inner collar is moved to the left it disengages with the outer collar, you can rotate it but the outer collar stays put. The outer collar provides the drive from the gearbox.  It sort of helps me understand, a bit!

Thank you to all who have contributed, it's nice to know there are people out there willing to help.

Chris

Edited By ChrisH on 04/07/2017 11:51:39

Great that you have it out.

Rather than simply replacing the pin with another 2 mm once consider re-emgineering things to avoid similar sheared pin jamming issues in future. I'd drill the holes out to 3.5 or 4 mm and make a new pin with shallow, taper sided grooves turned into it at the joint line. Threading tool with the tip rounded off worked for me. Half mm, maybe a touch more, deep should do fine. That way if it shears the break line and distortion will be contained in the holes so no smear to jam up. May still have a bit of twisting'n shifting to do to line things up before it can be punched out but that should be relatively easy. Light knurl on the collar ends held fine for me. Brass or aluminium alloy is often recommended for such pins. Never tried myself.

If confident that there is no shear risk I use rollers out of scrap needle roller bearings as pins. Keep a stash primarily to use as dowel and alignment pins.

Clive.

Clive - have freed off the box - don't know how or even what was binding but it's freed off now - and put the lot back. Like your idea for a 'shear' type pin and will do so in due course, has a 2mm nail in at the moment just to prove the system works, no more, got to sort out the toothless gear wheel next to get a run and then we shall see if all is OK! Getting there!

Chris