Wheel Plating

[springdetent]

I am aware brass mainplates and bridges get nickel + rhodium plated after finishing and decoration, but what is done with the wheels? I have seen a single source refer to this by saying the gear blanks are plated before tooth cutting, and a single video where they are plated after cutting (I'm fairly sure this approach is wrong, as the plating would come off the meshing surfaces and goop between the wheels.) No other watchmaking or repair resource I have found mentions the topic, but cannot imagine that Patek, for example, leaves their wheels untreated as they would tarnish. I have also seen a few movement manufacturers move on to using copper beryllium alloys for wheels instead of brass, but could not find any information whatsoever as to the specific alloy or finishing techniques used for that. Is there anyone here who could help clear this up for me?

[RichardHarris123]

Interesting question, I don't know either. 

[mikepilk]

I don't think they are ever plated, just machined from solid brass alloys, or gold etc.

See them being hand made : 

 

I've just stripped and Omega 620, so the wheels are a coppery colour to match the mainplate and bridges. I assume it's a brass alloy with more copper in to get the colour.  

Edited March 18, 2023 by mikepilk

[nickelsilver]

Generally speaking they are plated except for very cheap movements. Ideally they are plated before cutting the teeth, but not always, and it's not really an issue except for barrel teeth where there's just a whole lot of power. Beryllium copper is used for some watch gearing, yes, but only where needed- it is closer to steel in general strength and wear resistance than copper. But it too needs plating or it can turn quite dark. It would often be seen in autowind components or in some cases even ratchet wheels.

 

On old watches, like over 100 years old, if you look around the union of the pinion and wheel, you will often see dark tarnished brass. Back then (in Switzerland at least), wheels were cut oversize, then mounted on their pinion. In some cases the teeth were simple saw gashes, or they could be roughly formed. They were fit up with the mating pinion in a depthing tool and finished to size in a topping or rounding up tool. Finally, they were plated- but the steel pinion would be protected with a lacquer, thus the dark area of brass right at the mounted pinion.

[springdetent]

I wonder if they're gold plated then, as the color is closer to raw brass - I've never seen a rhodium plated/white going train, I don't think. And yes, neither Smith nor Daniels mention the subject at all, which is partly how I got confused in the first place. I'm sure if I could ask Smith he'd have an interesting answer.

[grsnovi]

5 hours ago, mikepilk said:

I've just stripped and Omega 620, so the wheels are a coppery colour to match the mainplate and bridges.

I've not had the bridges off the 620 I have but if you look closely you might see a wheel or two. Not nearly as brilliant as the bridges.

Edited March 18, 2023 by grsnovi

[nickelsilver]

Generally gold plated, could be rhodium or whatever. I worked on a bunch of Harry Winston Opus 7 pieces where the main wheel (3 wheel gear train) was blue. Inside of teeth not blue; those were expensive to make as there was a lot of beveling and graining to do before cutting the teeth- then cut the teeth without blemishing the finish.

 

Often dial side gearing like minute and hour wheel don't get plated, even on higher grade stuff.

 

 

 

Omega bridges plates and (sometimes) wheels were plated with a proprietary "recipe" for the copper color. I've read that tests have proven it's pure copper plate, but in my experience next to impossible to replicate with pure copper. But there are a LOT of variables in plating.

[mikepilk]

4 hours ago, grsnovi said:

I've not had the bridges off the 620 I have but if you look closely you might see a wheel or two. Not nearly as brilliant as the bridges.

 

It's hard to tell from the pic with the way the light reflects, but they look the same colour to my eyes 

(and that's before cleaning)