Bushing a hole in a thin brass plate

[AlanB]

Very rarely need to do this in a watch (as opposed to a clock) since usually the holes in thinner parts are jewelled and the ones that need bushing are the larger ones with more metal around them e.g. the barrel or centre wheel, but I have an example of a hammer pivot running in a thin part of the main plate of a repeater which has too much side shake and needs sorting. 

Are there any tricks to doing this, or should I (reluctantly) be thinking of the domed punch - which normally I'd avoid.

I'd like to add a photo but this is only really visible under the microscope and my microscope doesn't have a camera attachment.

[nevenbekriev]

Hi Alan,

First of all, I would'n worry about a hammer bearing wear as much as You do, espscially if a microscope is needed to see the wear.

No matter, the bushing in pocket watches bearings doesn't differ from the clocks ones, just the scale is different. You will need to make smaller bush in smaller hole. Acuracy is needed to make the things look good, as the result is seen on top of the movement. Usually it is harder to repair the verge side bearing for the crown wheel of small werge movements, as there is verry small surface and the plate is really thin, there it is beter to solder the bush than just press it, and riveting the bush in this specific bearing is bad idea

[AlanB]

That's a good idea to use a little soft solder - I don't think riveting is going to work in this location.  

Looks like I also need to bush the star wheel/snail, that's a bit more challenging.

[nevenbekriev]

59 minutes ago, AlanB said:

Looks like I also need to bush the star wheel/snail, that's a bit more challenging.

Please, do not do that before true understanding of the way the repeater works. First, I have never seen wear in this place, even in 300 years old pieces. No logic at all to expect wear there. Second - there must be free play in the hole where the bottom of the star sits, that is needed to ensure the wheel together with the whole lever on which it sits will sink when the repeater lever is pressed and thus unlock the function of repeating. If You see a problem that You need to solve, please, make video and show it here to discuss on it.

[AlanB]

Thanks - very much appreciate the offer of advice. I can explain the problem but can try and make a video. 

There is indeed play for the all or nothing piece that is fine.  What is causing the issue is that the snail can tilt on its arbor which lets the rack tail slide underneath it and then it has to go right in before it releases the all or nothing piece and consequently the repeater strikes 12 hours.  The rack tail is very thin (see photo where parts of quarter striking have been removed to show more clearly what is going on). I don't know if a previous repairer has "got at it" or if this is just for it to slide under the star wheel.   For hours 1-6 it generally works fine and becomes less reliable for the higher hours.

[It is probably worth saying this arrived in very bad condition as a "box of parts", so far I have

*silver soldered a cracked repeat bridge

* let in a piece to the main plate for one of the wheels in the repeat train which had cut right through the edge of a recess in the plate (ringed red in photo)

*new repeat main spring (missing)

*replaced broken screws in repeat bridge and shimmed the ratchet pawl which didn't hold properly

*new "comma shaped" cam to drive quarter rack, old one was missing.

I have plenty of experience with timepieces and making parts but not repeaters!]

It now works, quarters perfect, but sometimes gives 12 strikes...

Edited June 10, 2024 by AlanB

[nevenbekriev]

Ok, sorry, I have underestimated You skills.

What You describe, that the rack tail goes under the snail, may be is because someone has hammered thinner the rack tail in order to elongate it, which sometimes is needed for adjustment of correct strike numbers. If the snail/star wheel has big free play, then decision is rather to make new post for it. I am curiose to see how much the free play is present there. The post and the bearing are made of steel and will never wear, unless someone will decide to ream the hole. What is the free play of the bearing/post of the lever on which the snail wheel sits? But may be the beter way to solve the problem is to bend a little only the tip of the rack tail up.