Alexander master toolmaker

I have now managed to steal an hour away from Grandfatherly duties to get oily. I think I have discovered the second problem I have with the mill. Although when I first got it going, it would power up and down quite easily, but that facility ceased. Now as I examine it I can see why. When the hand control selects DOWN, the upper dog is engaged . However, the detent device is only in the mid position, confirmed by the mechanism being equidistant from both threaded end stops. When the lever is knocked back to neutral, the upper dog is disengaged, but the detent device is then hard up against the lower threaded stop - so there is no ability to select UP and engage the lower dogclutch.

The cause appears to be that the shaft has somehow moved down the machine! There is a gap of about 4mm between the upper dog and the machine casting, whereas the lower dog has almost disappeared from view - perhaps flush with the machine casting at the lower end. How it can have done this is baffling as both dogs appeared to be pinned to the shaft, it shows no sign of wanting to move any further - and the bevel gear at the very top of the shaft is still in deep mesh with its cross slide counterparts! Seems like this shaft is the next thing to have to remove form the carriage!

I will add a couple of relevant pics to the growing gallery and await your comments.

I think this is the most telling shot - the 4mm gap above the upper dog clutch.

I thought I would continue tinkering and started to strip out the motor drive shaft, first by knocking the pins out of the dog clutches and then from the bevel gear at the top of the nut to try and fix the problem. The dog clutch pin moved nicely but the bevel gear one is solid. Reluctant to hit anything too hard until all possible alternatives are exhausted I cast about a bit for other opportunities. Out of curiosity I took a copper mallet and tapped the botton of the motor shaft - and it moved! A couple more taps and the 4mm gap in the photo had disappeared! (I hadn't removed the dog clutch pins at his point, just tapped them about a mm loose) Immediately I could get UP neutral and DOWN on the select lever and everything thing was meshing and spinning wonderfully. Remarkably the bevel gear had not moved at all! It clearly has a taper pin holding it on the end of the shaft, but it appears that this pin must run in some kind of slot?

I tapped all pins back in as they had been and the whole system works fine! Presumably the pin has failed that secures the bevel on to the drive shaft, presumably due to the motor drive trying to raise the table but the rusted bevel stopping any upward movement - so the drive shaft was pulled down instead and sheared that upper bevel pin?

I think I now need to apply myself to drilling out the upper bevel pin (now it is in roughly the correct location on the shaft) , and try and get the shaft out of the machine to replace the taper pin? This is not going to be easy, but it's the sort of thing that would work really nicely until the nachine was boxed back up again - only to allow the bevel to freewheel merrily the first time the power drive was engaged!

Can anyone confirm with me that all I need to do in order to withdraw the shaft is to remove the pins in the top bevel gear, upper and lower dog clutches and the shaft should then just pull down out of the carriage?

Never a dull moment.

I wish I could remember, but its years ago since mine was in bits, and then it was my dad doing most of the work apart from the heavy lifting.

I do know he told me of some difficulty in removing the drive dogs, but I am reasonably sure that would have been the horizontal ones as the vertical parts were missing when he got it.

It sounds like you are on the right track though, and those pins are designed to shear if you have a crash.

Do you have a manual for your machine ?

I have just sent you a PM

Phil

Edited By Phil P on 30/12/2019 19:44:53

I think I now need to apply myself to drilling out the upper bevel pin (now it is in roughly the correct location on the shaft) ,

Exactly how do you know the bevel pin is in the correct position, to drill it out, if you cannot see it? Roughly is not near enough. I would suggest you move the bevel sufficiently before simply tapping out the broken pin from the shaft, thereby avoiding drilling into the shaft. Removal of the bevel drive (no longer pinned to the shaft) will allow the broken pin to be tapped out without any drilling

I don’t think I have ever come across a tapered pin running in a slot, so a new one on me.

A cross section of the Deckel FP1 is the same as an Alexander.

I think if the shaft had dropped a few millimetres, that would mean it was already coming adrift from the bevel gear.

So if the pin has indeed already sheared the shaft will probably drop out of the bevel gear fairly easily once the other pins are removed, after which you can remove the remains of the pin as described by NDIY above. 

Phil

Edited By Phil P on 30/12/2019 22:24:40

Well the shaft actually moved quite well after a tap, so I was hugely relieved and quite optimistic about getting it out of the bevel without much further effort. The problem of course is that you cannot actually get behind it with a drift to tap the shaft back down again! I wasn't actually being serious by the way when I suggested that the bevel gear pin must be running in a slot to allow for such movement on the shaft.

My outline plan was to knock out the pin in the upper dog clutch and then hope the shaft can be persuaded to slide down through the detent mechanism on its way to freedom? The diagram you have posted seems to confirm this?

The job will be tackled in the morning - before the next wave of family turn up for the New Year celebration!

I wasn't actually being serious by the way when I suggested that the bevel gear pin must be running in a slot to allow for such movement on the shaft.

Really?

Yippee! The shaft was extracted this morning and remains of taper pins also safely extracted. All I need now is a new taper pin to replace the old one and I can start the reassembly. The Deckel handbook identifies the pin as a "4 x 30 Din 1" which would probably not be far away but would be a different taper than an Imperial pin? Measuring the holes in the bevel gear seems to suggest 11/64" x 1 1/8" as the nearest fractional imperial size, so it looks like a job for the old Raglan - unless anyone knows where such a thing might be bought in quantities of less than 100?

Thanks again for all the help and advice given on this forum,

Dave

David, I can let you have 2 or 3 pins at 3,94 at the large end by 32,46 long if they are any use. If so just PM me with your address.

Brian

Or, a search on Ebay has possibilities

Edited By Brian H on 31/12/2019 14:28:03

Where is this 4mm gap your refering to?

Take a look at the photo, the 4mm gap is between the top of the dog clutch and the bearing tube as it emerges from the casting. You can also see on this photo that the selector quadrant is against its lower stop although the upper dog clutch is fully engaged.

As I discovered this was due to the lower bevel drive being rusted solid to the drive shaft lower down. As the machine tried to move the table upwards under power, the rusted bevel drive didn't allow the shaft to move, so the carriage moved without it - effectively pulling the shaft downwards, shearing the taper pin in the upper bevel drive and creating the 4mm gap you see. I hope that's clear - it isn't easy to desc ribe in so few words!

Does this help ?

Thanks , does mine look right??

In my limited, recent experience I would say yours looks fine. The 4mm gap I saw was the distance that the carriage had been pulled off the shaft, shearing the taper pin in the upper bevel gear in the process. There can't have been much shaft still within the bevel gear actually, although it still worked as the mechanism was turned by hand. The gap was the only indication that anything was actually wrong.

Normally the distance between the upper dog clutch and the upper bevel gear is fixed by both parts being located on the shaft by taper pins. In fact that is the only vertical location provided for the shaft, everything else being keyed to slide up and down it. There is a thick washer under the upper bevel gear, which may possibly be some kind of selective assembly fit as there are no other shims or packers in the system to eliminate any up and down movement. My guess would be that the thick washer maintains the optimum clearance between the upper bevel gear and the upper dog clutch to the bearing tube that sits between those two parts and sits slightly proud of the casting as it emerges top and bottom. The correct setting of the upper bevel gear into the two crown wheels within which it runs is then achieved by moving this bearing tube within the machine casting. Once set this tube is fixed in place by a pair of grub screws. The diagram posted by Phil P illustrates this relationship pretty well - although it only shows one grub screw holding what may even be a two part bearing tube in the Deckel machine whereas my machine has an upper and lower grub screw. .

To me it looks like the whole thing is designed to run for a long time without being messed about with - unless of course the machine is left outside for several years and bits get stuck together with rust causing a taper pin to shear!

You can buy just a single one here:

https://www.ebay.co.uk/itm/Qualfast-4x30mm-Taper-Pin-Turned/143060355755

and FWIW that listing helpfully also includes a note that "Standard inch-sized taper pins have a taper on diameter of 1:48 while metric ones have a taper of 1:50".

Edited By Bikepete on 02/01/2020 11:42:34

Doh! Well spotted Phil. Did seem like the price was 'ambitious' for just one...

Great to see this proceeding towards a successful conclusion - as a former owner of a very similar Deckel it is good to see it being given a new lease of life. Good work David and hope it serves you well once repaired.

David, I put some pins in the post for you this morning (02-01-2020).

Brian