probably a stupid question, but I'll ask anyway. I see a lot of people that have sent their rails in to a few different well regarded guys to "get them done" - what exactly is it that they do that is so special?
I know absolutely nothing about table set up or table mechanics or anything like that. As such, I have a hard time imagining what they could possibly do to for it to be worth the investment. I'm guessing you're looking at close to $1000 for shipping to and fro plus the work? Maybe even more?
Something to consider: many local installers may only be proficient in setting up a table and installing cloth (if anything..). Because of this, many opt to send their rails to a qualified technician, for any number of advanced modification.
As for the modifications:
Pool table cushions are mounted on an angled surface. This angled surface is what controls the nose height of the cushion, which has a huge impact on the way that the balls rebound from the cushion.
Older Brunswick tables, prior to the mid-1970's, used a cushion profile that is no longer made. Because of this, the old rails require a change to this angular surface, in order to accept a modern day cushion profile. Unfortunately, while the change could be made by running the rail down a table saw, it won't necessarily produce the best results.. As such, those of us who perform quality rail modifications will have custom-made tooling, which allow very precise modification.
In addition to changing the angle of the cushion mounting surface, it will also be necessary to adjust the height of the sub-rail (the top side of the cushion mounting block). This provides consistency across the rail set, as they could vary. While the work is performed, the tooling allows for the rails to be bolted down, the same as if they were mounted on a pool table. This ensures that the modifications will be "perfect" when the rails are installed on the table.
After the rails have been modified to accept a modern-day cushion, the pocket work is performed. A good technician will know which angles to cut the ends of the rails, to create the desired play effect.
Lastly, the technician will likely be very proficient in covering rails, with a high level of quality.
These are only the basics....
Keep in mind, many of these old rails could be beat up from repeated recoverings, and poor execution by past installers. It could be necessary to completely replace the sub-rail, which is not a job for amateurs.
Also, most of the technicians performing this level of work will also replace the floating nut inserts (Gold Crown II+) or the figure 8 nut plate (Gold Crown I) with a
Stafast threaded insert, which is much more robust.