I'll expand on my earlier post on annealing brass rails. I consider actions with brass rails to be exceptionally good quality, and the brass rail design superior in most ways; it is not susceptible to humidity swings, and it is more rigid in supporting good tone. Mechanically the design is more firm, as well.
First, the Schaff catalog still includes a brass rail duplication service, item 595. However, it doesn't show up in the actual online webstore, so I don't know if it's still available. The one time I had this done, I was very satisfied. No doubt a machine shop could also duplicate the rails, but the design is complex and the cost will be high. But if the rails are not damaged they can be annealed.
There is a likelihood that the brass rails are brittle, and tongues can and do break at their weakest spots (the notch for the centerpin, or at the screw hole). If the rails are intact they are brittle, but well worth saving and re-using. Brittle brass rails can be annealed to remove the brittleness by placing in the oven broiler at top heat for 30 minutes. This is true for unbroken brass butt plates too, but the brass is softer after annealing and butt plates are thinner and susceptible to bending.
If you doubt this, try bending an unbroken butt plate between two pliers. It will not bend, but snap, usually at the screw hole. But annealed, it will bend. The butt plates are a little more difficult, because they are more likely to have begun to break, and some will have hairline cracks you don't easily see. So it is preferable to buy new butt plates. These butt plates will fit the overwhelming number of American brass rail actions. (I HAVE used annealed butt plates with success, but it's sometimes very tough to see hairline cracks in the butt plate, so there's some risk - you can try to bend each butt plate after annealing with just enough force to break a damaged butt plate, to eliminate bad ones. Some shops have dismantled old butt plate actions, and the old butt plates might be useful as spares, if you're re-using butt plates.)
Brass is very expensive today, especially when compared to the cost of a short use of the oven!
Tokiwa makes a high quality butt for the brass rail, item 05 U508T with Pacific Piano Supply Co (Schaff has this part also).
Some builders have cost-prohibitive needs:
Chickering uprights with brass rails are an entirely different challenge, as the design is different, typically a Schwander return spring is used and the spring cord is tied to the brass butt plate. Further, the Chickering butt plate is very thin. I have replaced Chickering brass rails with Schwander butts and flanges with some success, and have re-used the brass parts too (a new cord must be made for the Schwander style spring).
Kimballs with brass rails are not usually worth the trouble, as there are also very thin butt plates for the damper flanges. These actions are usually too far along in deterioration. I find that the best Kimball verticals are those with a standard Schwander wood flange system. The current market for pianos will probably result in all Kimballs headed to the dump, but if grandma's piano HAS to be saved and money is no object....a spare Kimball action from a tossed Kimball will provide annealable used brass parts.
Finally, if your brass rail has a broken tongue it is possible to repair the tongue by silver soldering. This is a very strong repair.
Bill
Bill Shull, RPT, M.Mus.
Shull Piano
Period Piano Collection
909 796-4226