TromboneChat

If a trombone, lets say a Bach 50 with Hagmanns, was after market silver plated and the plating covered the inside of the rotor casing, but not the rotors themselves.

Would this be a problem for a trombone? Long term or short term

Not terribly likely.  Silver plating is less than one thousandth of an inch thick.  I doubt it would affect clearance (which is usually measured in thousandths -- more than one.

Further to the above comment, traditional electroplating requires movement of the liquid between the item being plated and the sacrificial metal supply ( silver), these areas such as the insides of tubes, or the insides of rotor casings / valve chambers etc are in a stagnant area of fluid movement, we find any plating happening in these areas to be incredibly thin. It can however affect the fitment of parts.

Most plating shops will cap of areas if you ask them too, so there is no chance of plating happening, but you need to specify this as most plating shops are not musical repair shops,

I had a customer pay a plating shop 1300 Australian dollars to have his trumpet replated in silver, nothing fitted any more when he got it back, it took around 6hrs of work to get everything to fit and slide nicely again.

Steve

I didnt think the plating should be too much of a problem... So how about this theory that the extra bit of material, the silver plate, causes the rotors to wear down quicker over time similar to a lapping compound?

Im trying to put forth a case in order to attempt to save an otherwise good Bach 50A3 from possibly being turned into scrap metal

Seems more likely that the brass rotors would wear off the layer of silver plating.

Quote from: Cubes on Aug 15, 2017, 10:00PMI didnt think the plating should be too much of a problem... So how about this theory that the extra bit of material, the silver plate, causes the rotors to wear down quicker over time similar to a lapping compound?

Im trying to put forth a case in order to attempt to save an otherwise good Bach 50A3 from possibly being turned into scrap metal

Brass and Silver are comparable in hardness, so unlikely one would exasperate the wear of the other, on the galvanic scale, Silver gives to Brass so no long term damage on this front.

Steve

I would prefer nickel plating for such a thing rather than silver plating.

John,

On a simple wear system like brass instruments, you normally have a soft and a hard side.  The brass case (and/or silver plated brass) would be the soft and the Piston or rotor would be the hard and nickel or chrome plated.

Whn refitting a valve they remachine the case to true it and replate the piston/rotor to tolereance, then finish with a hard coating for wear.

If you had 2 hard surface they would gall one another...

Quote from: john sandhagen on Dec 10, 2017, 07:14AMIf you had 2 hard surface they would gall one another...It's not a matter of two hard surfaces, it's a matter of similar (or identical) materials. Certain pairings (aluminum on aluminum, for example) will gall like crazy. Hardened steel mating parts usually won't gall except under extreme conditions. Of course, no one would want to make cores or casings out of steel (though we do now have some valves that use steel bearings).

I think it's really two soft surfaces that will gall most easily, but anything will with no lubrication.  And anything will be fine with sufficient lubrication.

In this situation, a "very" light lap with the finest compound should be all that is needed. There may still be a flash of silver on the inside of the casing, but it shouldn't be an issue.

John, we aren't talking about plating a rotor/piston for re-fitting here. We're talking about the outside of an instrument being plated, and a thin layer of plating being deposited inside the rotor/piston casing.

In the instance of building up a rotor/piston for re-fitting, then yes, nickel is the preferred material.

M

Doug is correct. Soft on soft galls. Running brass on brass with no lube will quickly create problems (assuming the fit is relatively tight)

M

Quote from: john sandhagen on Dec 10, 2017, 07:14AMJohn,

On a simple wear system like brass instruments, you normally have a soft and a hard side.  The brass case (and/or silver plated brass) would be the soft and the Piston or rotor would be the hard and nickel or chrome plated.

Whn refitting a valve they remachine the case to true it and replate the piston/rotor to tolereance, then finish with a hard coating for wear.

If you had 2 hard surface they would gall one another...

Hi John! I meant, nickel plating the rotor core is what I'd want to do. Apparently, I wasn't as clear as I had assumed.

Re-quoted...

"John, we aren't talking about plating a rotor/piston for re-fitting here. We're talking about the outside of an instrument being plated, and a thin layer of plating being deposited inside the rotor/piston casing".

M

Thanks, Matthew. I missed that from your original post. 

Thanks, Matthew. I missed that from your original post.