1914 'Trench watch' calibre ID and stem removal??

[Pict]

Recently rediscovered this watch - I think it belonged to my great grandfather. I'm interested in cleaning the case and fitting a new crystal. The movement runs. Does anyone recognise the movement or can tell me how I might go about putting an ID on it? The silver case has a Birmingham assay mark and a P for what I believe is 1914, along with the sponsor stamp for Zenith Watch Company.  

The watch has a screw on bezel which releases fine, so I need some advice on what style of crystal is required and how to correctly size it please. I want to use mineral glass rather than acrylic if at all possible. The original watch glass is missing so I don't have a reference.

I am also mystified as to how to release the stem on this movement. There is a well worn screw to the left of the start of the serial number, but it seems too far away from the stem to be the release. Might it be a split stem? Any advice on how to get the movement out of the case appreciated.

The only other issue appears to be a missing screw at the edge of the movement which I presume helps lock it into the case. Is this an item that can be replaced with any ease?

It is very dirty but the dial and hands are in good shape and I feel confident it will clean up quite well.

Thanks,

John

[ro63rto]

If it's one of the screws, they should move slightly when you pull the crown out to the setting position.

Sent from my Honor 5c

[Pict]

Yes I can't see anything move when I click the crown out and in.

[wls1971]

it looks like a variant of a three part borgel case screw back and screw bezel, the stem should be split and the movement held in place by a threaded movement ring, remove the back and screw the bezel back on and with the crown pulled outwards turn the bezel as if continuing to tighten and the movement should start unscrewing from the case. Three part borgel cases are quite rare they are usually two part. the case back actually srews onto the rear of the movement retaing ring.

The missing screw retains the movement in the threaded movement ring,

you may find this site useful for this watch,

http://www.vintagewatchstraps.com/borgel.php

Edited May 4, 2017 by wls1971

[wls1971]

Tthe hallmarks show that the watch was imported into England in 1914 through the birmingham assay office and the Z.W.C sponsors mark is for the Zenith watch company as you have already stated so just use the ranftt movement site you should find a match on there

Edited May 4, 2017 by wls1971

[Pict]

The crystal bezel is screw on, but the back is a snap on. I removed the remaining screw that retains the movement at the edge of the case, and the movement wanted to fall out, but was off course still trapped by the stem. I don't think I saw any sign of a threaded movement holder, so I don't think it is a borgel case as you describe. I will take another look tomorrow and double check. Thanks for the info.

[clockboy]

I think it is the Borgel design. If so then the whole movement should drop out much the same as you would with a pocket watch. The stem has to be in the out position the remaining case screw removed. However having read the excellent link by "wis1971" posted it might have a small screw in the side of the stem to release the stem. Keep us informed I and many will be intrigued. 

 

[Marc]

The missing movement retaining screw isn't missing, it's in the wrong place; what's missing is one of the bridge screws.

If you look at the two screws to the left of the S/N you'll see that one overlaps the other. Compare that screw head both with the other two bridge screws and with the other movement retaining screw; you can see that it has a larger head to overlap the edge of the case thus clamping the movement in place, and a bevelled edge to provide clearance for the case back, just like the other retaining screw. The correct bridge screw has a smaller diameter head so that it fits into the counter sink in the bridge, and a tall enough head such that it sits flush with the surface of the bridge. The top of the head should be squared off with no bevel as is the case with the other two bridge screws.

If you put the movement clamping screw back in its rightful place then try the other bridge screws in the vacated hole to see if any of them fit without the end of the screw fouling anything on the other side of the plate then you will hopefully have one you can use as a pattern to measure. If you let me know the thread diameter, the head diameter, the thread length, and the height of the head, I can have a look and see if I can find a match in my stash of spares. The only variable then will be the thread pitch which could be a problem but it's worth a try.

It could be a split stem Borgel case as Wls1971 suggested but that then begs the question "what is the function of the (well worn) screw?" It could be a dial foot clamping screw but if that were the case then I would expect to see another one roughly opposite it, which I can't. It could however be the stem release screw. Even though it is a fair way from the stem this is not a reliable indication that it doesn't perform this function as there are various designs of keyless works that could displace the screw further from the stem than might be expected. If it were me I would loosen it off and see what happens. If it does release the stem but the movement still won't release then you could still have a Borgel case.

The crystal should be fairly easy to replace. If you measure the opening using calipers then order the next size up; you don't want it to be a drop in fit. You will need to heat up the bezel so that it expands enough to admit the crystal and then locks onto it as it cools. It might be wise to get one each of the next two sizes up so if one is still loose you have a larger one to try. Most supply houses carry round mineral glass crystals, both flat and domed, in a wide range of sizes and they aren't expensive.

By the way, that's a nice watch. Serviced and cleaned up it should be a good time keeper, and of course a fantastic heirloom.

 

[wls1971]

I have based my observations about this case on the following, although the case back may snap on and off, the back seems to have a thread running around the inside, please look at the back carefully under a loupe to determine if this is the case, because snapping it on and off may eventually strain the back to the point of it no longer fitting correctley,

The case is a silver case but there appears to be a diffrence in the metals looking from the back of the watch with a clear ring around the movement again look very carefully at the edge of this ring under a loupe the high res pictures you have supplied appear to suggest to me a thread

The screw looks to be some kind of dreadful bodge carried out in the past and is a badly mauled plate screw and it appears that someone has drilled a hole next to it and inserted the movement retainig screw there

[vinn3]

the stem is held in place by a collet - much like a pocket watch.  if the stem is too long or is rusted in place - the mvt. wount come out.  just like a pocket watch.  I suggest applying  penetrating oil to the stem and wait for it to work.  good luck.  vinn 

[Pict]

Clockboy, when the sole remaining movement retaining screw is removed the movement does want to drop out of the case, but with the crown pulled out to the hand setting position the stem remains attached and is visible entering the movement and won't let go when you try and ease the movement away. I don't see any screw heads in the stem tube either.

Marc, I had a closer look at the misplaced movement retaining screw. When removed it is similar in design to the other one but is a larger thread and does not fit the vacant movement retaining hole (too big). It conceals a very crude countersink, but the rebate for the original screw is still visible. I suspect someone stripped the bridge screw hole and tapped it for a larger thread and used a spare movement retaining screw from something else as the new bridge screw. I'll see if I can measure the current thread and the old head diameter.. as you say there may be the possibility of getting a screw with a more elegant fit, and I appreciate the offer to have a look. 

wls1971, you are right - I need to pay attention and look closer. The case back looked to be snapon as it is already distorted and appeared to have a case knife slot. It is in fact threaded and will still thread on. I should be able to clean the threads and remove some of the distortion in the case back in due course. I don't think that it threads onto a movement retaining ring though I might be wrong. I cleaned the junction between the thread and the case but it is impossible for me to tell whether it is part of the case or a threaded ring. Looking at the inside of the case with the movement tilted out, I'd guess it was part of the case - metal colour is uniform fresh silver on the inside surface.

Removing the only remaining case screw and removing the crystal bezel allows the movement to tilt out the top of the case as expected. With the crown pulled out to the hand setting position however, the stem still appears to be captive in the movement. I can move the movement away from the case about 1mm until the crown hits the end of the stem tube, but the stem appears to be attached to the movement. If I wiggle the movement around the stem will also wiggle laterally in the case stem tube a little, so it doesn’t seem like the tube contains any tight fitting détente spring sleeve, as might be the case with a negative set movement. The crown cants at an angle also in line with the tilted movement so I presume this can’t be a negative set movement? http://www.vintagewatchstraps.com/watchmovement.php#posnegset

[Pict]

Also meant to say that the small distressed screw under the bigger screw on the barrel bridge doesn't seem to do anything. I tried turning it a few turns while pulling the crown and nothing happened. This screw turns with very little resistance and does not appear to thread out or in when turned. Not sure what it is or if this represents another stripped thread. It looks like it widens out into a larger diameter flange under the plate... sort of visible in the photo.

Edited May 4, 2017 by Pict
Forgot to mention something

[clockboy]

I suspect this is how it is supposed to come out but damage or dirt is stopping this or it is a split stem. If it was me I would first try pulling on the stem to check if it is a split stem BUT not to much force. If there is still no progress then I would remove the crown wheel,ratchet wheel then remove the bridge.You might then just be lucky and be able to see how the stem is attached. PS power must be removed from mainspring first.

[Pict]

Thanks clockboy, I've tried pulling fairly hard on the crown with no luck. The stem may be split but I am reluctant to try harder. Removing the bridge may well be the way forward. The stem appears to function correctly in both positions so getting a glimpse of the keyless work would be a big help I think. I need to do some study before I dive into disassembly though, as I've only rebuilt quartz mechanical movements thus far.

[Pict]

Found the solution to getting the stem out. The situation was much clearer once I removed the barrel bridge. The small slotted screw that sat under the bad bridge screw repair is actually the end of a 'sliding post'. This post has a rebate in it that carries the end of a spring bar that runs across the stem and stops the stem pulling out all the way. The solution was to remove the dial and push the post in from the other side to raise the locking bar and release the stem. This post was possibly threaded at one time so you could screw out the post from the backside and release, though the protruding end on the dial side is rounded like a little button so maybe it is meant to just be sliding and not threaded. Seems a daft design if the dial and hands indeed have to be removed to release the stem. The story will be clearer on further disassembly. 

[transporter]

Well done mate, for the case I would soapy water in an ultra sonic first, then silver dip then polish it up, the dial I would do what ive just done on an old enamel dial (see my latest post) use a streradent tablet and it will come up gleaming, and inest in so L&R ultra fine cleaning solution.

[Pict]

Your watch came up really well. The steradent looks to have lifted some of the dirt from the dial crack, which is an issue I have as well between the 4 and 5 hour markers. How much water did you use with one tablet and how long did you immerse it for please? I'd like to try that technique but I'd better have a close look at the dial and make sure the lettering is enamelled.

[transporter]

Just a standard drinking glass of warm water and 1 tablet for 3 mins, I think you should be safe with the numbers as the cleaning is very gentle