Bushing an egg-shaped hole without a lathe

 This wasn't the smartest idea I've ever had. My 1-jewel Swiss movement had an egg-shaped hole for the barrel arbour in the bridge and it couldn't be fixed properly with a staking set. Here we can see the result after hammertime - one axis was fine but the other was too wide. 

The accepted way to fix this issue is to use a lathe to increase the diameter of the hole so that it becomes perfectly round and centered then use the same lathe to make a bushing, use a depthing tool to center the hole and add a hole to the bushing.

But what if you don't have a lathe, you have too much time on your hands and are stubborn?

Bergeon supply some brass bushes in different sizes so it is possible to take take one of these and with quite a lot of work use it for the hole.

A bushing with the right outside diameter needs to be chosen, has to be quite larger than the barrel arbor. In this case 2.3mm was chosen.

 

 

The width of the hole measured so that the bushing can be ground down to the appropriate height. 

0.5mm needed to be removed. Sounds like very little but when considering that the amount to be removed needs to be exact and has to be done by hand this was quite a laborious process. Not difficult but time consuming.

Polishing frog was perfect for this. Some superglue, 1000 grit sandpaper and some elbow grease. No photos of the actual grinding but imagine there's one. 

 

Took quite a few grinding and measuing loops but got there eventually. Just a tiny fraction of a mm oversize, so good enough.

 

 

 The hole in the bridge now needed to be reamed out while making sure it is centered but luckily the Seitz master tool has exactly the right tool for the job.

 

 

 

This tool is meant for centering the jewel but the Chicago School of Watchmaking book explains how to use the tool in exactly this situation. The book suggests a pump center from the bottom and not 30155 but the latter works just fine for this purpose.

 

 

                                                                                     

The movement held in place, centered by the lower centering pin and reamed. Unfortunately the distance between the plates was not enough for the reamers to work properly but once the hole was rounded the last reamer could be used on it's own. The hole was centered and rounded and the reamers are self-centering so the final pass can be done, very carefully, without the centering set.

 

The bushing's hole then needed to be reamed to size. No photos, but this the Seitz setting holder, and reamed as above until the desired width was achieved.

 

Everything had to be deburred.

 

 

 

And then it was just a matter of pressing the bushing in place. The first photo shows the a flat anvil in the Horia tool but this wasn't used as it was too large, allowing the plate to flex. A proper sized anvil (250) was used instead. Bushing was placed on top of the hole from the bottom and pump pusher larger than the bushing used. My Horia set doesn't have a large enough size but the Seitz pushers can be used in the Horia tool. Just add some light oil to ensure good fit due to the age of the pushers (my Seitz set is from 1938) and tolerance differences.

And, that's it. The hole is now bushed and the barrel arbor has much less side-shake.

Will I do this again? Probably not because it is way too much work to do manually and it is too easy to screw things up. But a great learning experience to do at least once.

Depthing tool

 Depthing tools are used to make sure that the distance between pivot holes is correct and is useful when either making a movement or when working on unjewelled pivot holes, or barrel arbor holes.

These tools were manufactured in large quantities during the late 19th and early 20th century but not anymore because our modern technology allows us to calculate every detail of a watch movement. Still an invaluable tool when working on old movements with unjewelled holes or when manually making a movement scratch.

Operation is pretty straight forward. Both wheels are inserted in the runners and made to mesh at the correct height.

 Here we can see the result of a third wheel and a center seconds pinion being too close to eachother - the teeth are stuck.

 

 

Screw at the bottom is then adjusted and the wheels turned until the meshing of the teeth and pinion are just right. This is based on feel and experience, both of which I lack but it is possible to get the hang of it and get decent results in a short time.

 

 

 

 

Once the correct distance is found the movement can either be marked or the pivot holes checked. The tool needs to be completely perpendicular to the plate for this measurement to be correct.

 

 Here we can see that the holes are too close together; the left hole's center is ever so slightly to the left of the pointed tip of the tool's runner. This caused the wheels to bind and happened because the holes were not broached before being closed with a staking set.

It was possible to move the right hole by gently broaching one side causing it to become a little eggshaped and then broaching and finally closing with the staking set. A time-consuming and difficult operation because everything needs to be just right and a few hundreds of a millimeter make a huge difference. This is also something that cannot be done very often as a lot of material is lost during deburring so it will decrease the time before the hole needs to be bushed, probably by quite a lot.

Elgin 303 - 7j 1924 12s pocket watch on it's last legs

 

https://pocketwatchdatabase.com/search/result/elgin/26664950

Previous watchmarkers' marks, not really significant but always nice to see. Quite a few of them around the case so the original owner probably took good care of it. At some point, probably after the original owner died the watch was used for a long time without any servicing causing the pivot holes to become so egg-shaped that the escape wheel would not turn unless helped.

 

This 101 year-old pocket watch hasn't been serviced in a very, very long time. The case, however, is in immaculate condition which in this case is like getting the movement for free.

 

Wear to the plating causd by out of round pivot holes. 

 

 

At some point one of the barrel bridge's screw was either lost or broken. A watchmaker made a replacement that doesn't fit quite right, was slotted very poorly and wasn't finished and it seems that the material used was quite poor. No lathe at the moment so it will stay as is as buying replacement screws is too expensive. The other option is a donor movement but it isn't worth sacrificing a whole watch for one single screw.

 

Even if this is a 7j watch it is still well made, just a cost cutting measure to allow everyone to own a well built watch that would last but compromises on timekeeping ability in order to reach a certain price point. The movement is still decorated to a good standard, so much better than the Swiss in the 1970s who would only decorate the very high end movements. Evem the balance well and the bottom of the mainplate are decorated, something that only watchmakers would ever see. They really took pride in their work and it shows.

Here we see the results of an ever escalating patent arms race. Not much has changed in the logic of watches in the past two hundred years, and Americans, as Americans do, came up with a large variety of setting and winding mechanisms in order to patent and market the watch.

Also visible is part of the lever setting mechanism indicating that this model is based on a railroad grade design. The lever doesn't go out of the movement so it cannot be used but it must have been cheaper to produce an extra part instead of re-tooling the whole manufacturing and assembly lines.

Escape wheel pivot holes all shot, need to be bushed. Never did this repair and it can go sideways really quickly.

 

 

Fourth weel is almost as bad, needs a bushing too.

 

Barrel, second and third wheels weren't as bad and the staking set fixed them.

 Fixing the center wheel holes. Both needed it. 

 Badly worn barrel hole. Clearly someone added stupid amounts of oil just to be able to say that the watch works. A common tactic used by unscrupulous watchmakers and sellers.

 

 

Progress was slow but steady and the result is quite excellent. 

Center wheel was next. Compare the before and after; run so much better after fixing the hole. Still need to ream the edges of the hole and to burnish the pivots so there's still some extra friction at this point. Both top and bottom holes needed help.

 

 

 

Blueing screws using heat

 First polish, then heat just enough.

 

First attempt; not great.

 

 

Second attempt was much better

Fixing a worn pivot hole

Lower quality watches cut costs by reducing the number of jewels in a movement. A 17 jewel movement is considered fully jeweled, 15 jewels are still quite high quality but it is all downhill from there.

7 jewel movements wre common, especially pre-1960s and were regarded as everyday watches for everyone which were still of decent quality as pallet fork and balance were properly jewelled. Anything less than 7 jewels would never function properly but these types of movements, especially one jewel ones were common in the 1930s to 1950s as extremely cheap, mass produced watches truly for the masses.

Jewels, made of synthetic ruby (or garnet and even glass in some cases for cost-cutting reasons) are extremely hard and flat thus providing a perfect material for bearings. Watch wheel pivots are made of hardened steel so the jewel will never wear out and with proper maintenance the pivots will also stay in good shape for a long time.

 There is a problem with unjewweled pivot holes. Watch plates are made of brass, most often plated with nickle, rhodium or some other metal. This means that unjewelled pivot holes are softer than the hardened steel pivots that ride inside them so eventually, and especially with older natural oils the pivot hole would stretch, become larger and go out of round.

There are two ways to fix this situation, either by closing the hole with a staking set or by completely cutting out the hole and inserting a friction-fit hard brass bushing. This is generally expected to be manufactured by the watchmaker so not every pivot size and bushing diameter combination are readily available to purchase. Such manufacturing requires a lathe.

In this post I'll show the repair of a worn pivot hole using a staking set, a smoothing broach and a reamer.

 

The pivot clearly cannot turn properly in the hole and sometimes rests at an angle. Other than causing increased friction at the pivot, the wheels will suffer from increased friction due to unoptimal meshing between the teeth of the wheel and the next wheel's pinion leaves. The whel here would barely rotate when blown at with a hand blower even if no other wheels were installed.

Always, always mark the hole. Update: round off the hole with a broach before proceeding! If not done this can cause the hole to wander just enough to cause the teeth to bind in the pinion.

Two rounded punches need to be used. A flat punch/stake can be used to support the hole from the bottom instead of a rounded punch but I find that doing this does not close the hole evenly vertically, with the bottom being wider than the top.

 

Tap tap tap.

The hole after closing with the staking set. A new inner ridge has formed where the hole closed. This also makes the hole round but there's a limit to how far gone a hole can be rounded with this method.

Checking the fit; pivot barely fits now.

Smoothing broach.

 

After broaching the pivot fits with just the right amount of play.

The hole from the top, nice and round. Broaching the hole causes a small burr to form on the edge so it needs to be deburred as otherwise oil would get stuck around the burr instead of flowing around the pivot. Due to the holes being so small (around 0.24mm in this case) a reamer needs to be used for deburring.

Seitz jewelling tool 106 reamer and reaming handle, perfect for the job.

 

The pivot in the hole; doesn't look like much but that's the point: if somethng would be noticed it means that something is wrong. Should look like a normal pivot in a normal hole.

 Both top and bottom holes will probably need this treatment and here we can see the difference fixing one or both holes makes. The first video is with the top hole fixed, an improvement surely but it is obvious that there's extra fiction.

With both fixed and a little 9010 oil in the top hole. The difference is massive and will help the watch run better. This has to be repeated for all unjeweled pivots which is a time consuming, exact task. Not difficult to be sure but there's quite some checking and re-checking. A fairly expensive repair due to the time involved and extremly specific skills required.

Junghans 620.00: bad manufacturing

 This one was torture. The movement had a broken escape wheel and missing exit stone so got a 620.52 donor movement.

However the movement was basically unservicable due to every steady post in the movement being extremely tight, badly finished or even crooked. So this movement commits the worse sin of all: horrible manufacturing.

The balance wheel was also warped and while trying to get the hairspring out it broke. 

 The donor did not have the same problems but unfortunately it did not fit in the case.

 And that horrible integrated barrel arbor/ratchet wheel design is just horrible.

I want to forget I ever came across this movement. An expensive lesson.