This is #12 in my series of basic watchmaking tips.

Combining two shorter topics here, because of a need I see on the forum for one, and a request was made to me via PM for the other.

First fitting a new stem. Now this is just the way I do it – you don’t have to follow this, but it works for me.

Here is a new stem and crown that needs to be fitted to a watch:



New stems tend to be very long, so I like to get them cut down first to something close, to make it easier to fine tune the final length. With the movement fitted into the case, install the stem – fully install it so if it uses a screw to lock the stem in place, make sure it’s locked down:



Now mark the stem right at the end of the case tube:



I typically mount the stem in a pin vise through this process, but when you do so, make sure that the 4 jaws of the pin vise are clamping on the 4 flat surfaces of the stem, and not the round surfaces:



Clamping on the round surfaces can raise burrs, that then essentially become cutting tools that will chew up the soft brass in the main plate:



Now cut the stem at the mark you made:



You can use different things to cut the stem, but I just use side cutters. This will leave a rather jagged end, so if using this kind of tool you have to be aware that you need to cut it in such a way that you can clean up that jagged end, and not have the stem too short. It won’t be too short here of course, because you have left plenty of length.

For cleaning up the end of the stem, there are different tools you can use. If you cut it with a Dremel cut off wheel, it will be pretty clean already. But if you need to remove uneven material, you can just use a small file. I tend to use a stone – holding the stem end against the stone, I move it in a figure 8 pattern that you can see on the stone. Using this pattern keeps the stem end perpendicular to the threads:



I always put a very slight chamfer on the end of the stem that I just cut, before screwing the crown on:



Next I install the stem and crown:



The next thing you need to do, is determine how much stem you still need to cut off. So something to use as a gauge is helpful, and I often use a screwdriver blade:



I can then remove the crown, hold the blade to the stem, and determining exactly how many threads I need to remove from the stem. Then it is given the final trim, and fitted to the watch:



Now if you want to use Loctite, apply a small amount to the threads of the stem, and then screw the crown on - back the threads out, then screw it on again. Of course the stem itself should be properly lubricated, as well as the case tube and crown gasket.

Note that there is a very small gap between the case and the crown. This helps ensure that you don’t cut it too short if there is some play between the movement and the case. It also helps people grip the crown better when they need to move it to the time setting position. Not sue much an issue with a large crown like this, but it can be with small crowns on smaller dressy watches.

If you have any questions on this, please ask.

Next post will be on screwdrivers...

 

I did pretty much all these things ....except using the case tube as a marker and the screwdriver as a gap gauge. Good tips for my next attempt when I get the 2165 crown closer the the case by about half.

As usual, greatly appreciate the pertinent content!

 

I have noticed in my re-reading of the technical and theory books quite a bit of admonition for burring parts. Especially the center wheel and sweep pinions.

 

@Archer what is a split stem and why do I hear that they are tricky? My Constellation has one… but I only know that because Ashton said so…

 

Split stems are typically for front loading cases, where you cannot release the stem from the movement while it is still in the case.

So the stem is in 2 parts. One is the movement part “with beak” as Omega refers to it. So it has the male portion, and the part in the crown is the female portion. The stem is fitted in much the same way, just that you are only trimming half the stem.

Not really more tricky, but if there is wear or the tynes on the female part are sprung, the two halves can come apart too easily.

 

Thanks for your time archer.

 

Okay moving on to screwdrivers...part 1

Screwdriver types and fitting.

There are generally two types/shapes of screwdriver blade shapes out there. The wedge shaped and the hollow ground. In addition to different shapes, different materials are also available.

Here is a copper bronze wedge shaped driver:





This is a high speed steel (tool steel) hollow ground blade:





Just to nail down some terminology first, when I refer to the length of a screwdriver blade, or the slot of the screw, I’m referring to this dimension:



If I refer to the thickness or width, it’s this dimension:



In addition to differences in screwdriver blades, there are differences in screws, so I wanted to show this as it can be quite extreme.

The photos above are from an ETA 2824-2, so this is a very modern screw:



Here is one from an Omega Cal. 1120 (so ETA 2892):



Many modern screws have very wide slots in them compared to vintage screws. This is a screw from a vintage Hamilton 980:



This is from a vintage Omega 30T2 movement:



As you can see, the slots in these vintage screws are narrower. But they also have another large difference – they are much deeper slots than modern screws. Back to our ETA 2824-2 example:



So a wide and shallow slot. Same thing with this ETA 7750 screw:



Back to the vintage Hamilton – the slot is cut much deeper into the screw head:



And here is an Omega 321 screw – again the slot is cut very deep into the screw head compared to a modern screw:



These differences are why many watchmakers, myself included, have more than one set of screwdrivers. Here are the two sets I use:



The top set are VOH screwdrivers, and these are dressed generally more in line with vintage screws, so the blades are narrower at the tips. The lower set is made by Horia, and these are dressed more suitable for modern watches.

When selecting a screwdriver for the job, the first thing to look at, regardless of the type of blade you plan to use, is the length of the slot. This is equal to the diameter of the screw head.

Screwdrivers are sized in mm, so a 100 size screwdriver is a 1 mm blade. A 160 is a 1.6 mm blade, etc.

If you select the blade that is too long, the ends of the blade will hang over the screw head, and possibly gouge up the chamfer in the movement plate. The place I see this most often is around the setting lever screw, that releases the crown and stem from the movement, like this:



And this:



If you select a screwdriver blade that is too short, it can cause damage to the slot. Back to our Hamilton 980 screw, and you can see here the arrows indicate the length of the blade that was used, and the damage it caused to the slot:



I see damage like this a lot, where a blade that is too short is used. Sometimes it might be because the person doing the service doesn’t have the right size, but sometimes it appears just to be laziness where they can’t be bothered to put down one screwdriver, and pick up another.

Here is the ratchet wheel screw on a Panerai that uses an ETA 6497, and you can see that the screwdriver that was used was not nearly long enough:



Here’s another from a Panerai, and the upsetting thing is that it had just been serviced by Richemont. I would expect the service center for this brand to equip their watchmakers with the right tools, but maybe not...



All that is required is to use a proper 300 screwdriver:



To be continued...

 

Great explanation. Do you have a set of jis screwdrivers?

 

I don't know which OF member requested this via PM but I, for one, am glad they did because this is fabulous, thank you Al!

 

Thank you for the very informative post!

It is neat to see how different the slot depths are on vintage and modern screws. I wonder if one design is easier to work with? I also wonder why the trend towards shallower slots?

 

@Archer I will never work on a mechanical watch but I was recently using my Canadian Tire set to remove up to 7 screws on some cheap battery powered watches. Some of the screws appeared to be magnetically drawn by/to my screwdriver while others weren’t. Are all watch movement screws made of brass? If not, does this magnetic event occur to you and can it magnetize a watch?

This is my Canadian Tire set. I will stick to eyeglasses and cheap digital watches with this one.

 

Continuing...

The next thing is what thickness of blade you are going to use, and that will depend on a few things. As I have illustrated, it’s partly determined by the type of screw, so a 160 modern screw might require something very different that a 160 vintage screw.

Here is what you don’t want – the tip of the screwdriver blade contacting/riding the bottom of the screw slot:



This is for a couple of reasons, the first and primary one being that the blade will be far more likely to cam out of the slot if the blade tip is touching. This can lead to damage to the screw head, and to the surrounding materials when it actually does slip. Gouges and scratches on movement plates are common from this type of error. Another reason is that on some fully blued screws, the bottom of the screw slot is also blued, and if the blade touches it, it can damage that bluing.

Here is how the blade should engage in the slot:



The tip of the blade should just be above the bottom of the slot. This ensures that the sides of the screwdriver blade are firmly engaged with the screw, and cam out will be far less likely.

So what type of blade should you use? Well, the watchmakers I know use the standard wedge shaped driver. I’m sure there are some out there who use hollow ground blades, but I’ve never felt they offered any real advantage over the standard wedge style. Here is a hollow ground 160 blade (which is the proper length), in that Omega 321 bridge screw:



So right way, the blade is bottoming out in the slot. On a vintage screw like this, I could make it work by shortening the tip of the screwdriver blade so it doesn't bottom out. But on a modern screw like our ETA 2824-2, that would be very difficult to do and you would have to remove a ton of material from the blade to make it not bottom out on a shallow and wide slot like this:



So there may be a use case for vintage watches, or possibly modern watches that have more vintage-like slots in the screw heads, but for most the wedge style blades are the better choice.

The one area where I do use the hollow ground are for very round headed screws. Most watch screws are flat head screws, or perhaps have a very slight rounded head. When I encounter a fully rounded head, it’s usually a case screw of some kind, and the one that I use a hollow ground for often is the screws for the Panerai Luminor watches, that hold the crown lock device in place:





So, now that we have talked about the types of blades, types of screws, and how you want the two to fit together, how do you dress these blades to make that happen?

Hollow ground blades require some special equipment – I don’t have that equipment, but here is a link to one version:

https://www.esslinger.com/horotec-watchmakers-screwdriver-sharpener-msa-01-504/

Cost is about $400, and as you can see it has round stones to create the hollow ground profile:



Of course there are other ways to accomplish this – taken from another forum where a member there showed his technique:



So not an easy task. For a standard wedge shaped blade, there are different tools available – this is a roller style jig that I bought many moons ago:



It’s a roller system that grips the screwdriver, and allows you to move in on an abrasive surface of some kind. That could be a stone like I’m showing here for demonstration purposes, or it could be a file, or even abrasive paper/film that is on a hard backing.

I was simply taught to use a small file:



I have a piece of wood that is in a drawer at my bench, and I’ve used a file to cut a V shaped notch in it, and I put the screwdriver into the notch, and use the file to dress the blade. That does take a fair bit of skill to keep the blade sides parallel to each other, so using a jig of some kind can make the job a fair bit easier of you are just starting out. The one problem with the roller style jig I showed above, it uses a bearing on either end and over time debris has entered one of those and seized it up solid.

So to make the blade fatter, you just shorten it. To make it thinner, you dress the sides to make it sharper. It doesn't get much easier than that.

I hope this helps.

Cheers, Al

 

No, I do not.

 

There are a lot of variables that determine how easy they are to work with. Some screws are terribly soft and easily damaged, while some are very hard and difficult to damage.

What I would say is that the screws with very shallow heads can be problematic, in that the heads can split. So you end up with half the screw head still attached to the threaded part of the screw, and half snaps off. You then have to use the half that is there to unscrew it and install a new screw.

Also, if the slot is cut deeply into the screw head, it can cause the head to twist right off quite easily. I find this happen a fair bit on Speedmaster movements (861 and following series) where they use larger headed screws with fairly thin heads for attaching various chronograph parts.

In general, I would say vintage cause fewer issues overall.

 

No, the screws are typically made of steel. There are some exception - the very small screws on the balance may be made of a brass alloy, or even gold, but most are steel.

Part of maintaining your tools is to keep them free of magnetism, so this includes screwdrivers, tweezers, etc.

 

Very interesting, thank you for sharing these insights!

I had not thought about hardness, or head/slot design as it pertains to potential failure.

 

Thank you Archer for this thread and for the fine photographs.



I would like to replace a couple of case screws in a couple of pocket watches I have on hand here. Would this set provide the proper fitting screwdriver for the task?

I ordered out a couple of proper replacement screws for these Illinois watches.


The movement is loose in the case because of the broken case screw. I will need to extract the remains of the screw before replacement.


This movement features gold screws, one of which was replaced at some point. I have a gold screw ready to install as replacement for the silver headed case screw, but no screwdriver to fit. Even the screwdrivers from an eyeglass repair set won't work. I'd prefer proper screwdrivers for the purpose rather than attempting to fabricate something.


Any advice suggested will be appreciated.

 

Very informative as always, thank you once again for taking time to pass along your knowledge.

 

I find on the older wrecked screws tend to tear up the nicely dressed screwdrivers. So I keep a set of cheap screwdrivers for working on them.

Over the years I have acquired different dressing things like @Archer showed. What works best for me is a diamond hone. Not unlike the small file shown. I do have the roller thingy. It is really easy to grind groves into the dressing stone. The bearings also get bunged up easy.

I also have a large slow wet grinder (from the enameling days) which I use for roughing things out. When I got the 21s century watchmaking book by W.O. Smith Jr. I Impulse purchased a crocker tool and motorized diamond lap (for graver sharpening.) There is no panacea that can replace in person mentoring and experience. I only ever used this fancy system once in nearly 30 years. Setting up the water cooling drip system is a real PITA.

While the fancy boxed sets with ergonomic handles are pricey. The replacement blades are not. The handles are also sold individually. These were common at the NAWCC marts and seem to pepper eBay. I suspect a lot of folk get them and find they are not magic wands. My favorites are some of the old ones that fit my hand well. This is another place where having someone watch to correct bad habits is probably a good thing.

One of my other fantasy projects is to make a dremel jig should I ever want hollow ground drivers.

One thing that was impressive on the factory tours, was how the drivers fit the screw so well, they could pick up the screws and place it with almost a single motion. That sort of skill can only come from in person training and a lot of practice.

I personally would like to know more about broken screw removal. The Alum works great when the metals differ. When one has a broken scres in a barrel arbor or chronograph bridge, such can not disolve out. And the bergeon 30209 tends to tear around the edge of the screw, or the points simply smashes. I found I had to make and dress my own points with mixed results. Barrel arbors are not drilled through so this style tool can not work.

Kano slikroil and Evap-O-Rust do seem to work. This dicolores the screw as they chemically convert the oxide.

Drilling is the last resort. The drill however tends to wonder. Micro endmills may be a better option they break when one looks at them. If drilling is done, such has to be in the lathe with a face plate. (I forgot this and attempted to use the dumore) PcBoard drills used to show up in the surplus stores. These also break when you look at them. Harbor Fright had some last week unmarked so out of tolerance rejects. These are designed to work in air bushings at 20 to 30000 rpm. Dremmels are simply slot car hobby motors with a chuck, so they are not really precice enough. The drill will alwasy bite into the soft metal surrounding the screw,

In production and warranty repair, it is much simpler to replace the part than fix it. Would like to know though if there is a better way?