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