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After replacing grand damper guide-rail bushing cloth of the proper thickness , how does one burnish or "size" the bushing for proper fit if it turns out a little bit snug?

Try inserting bridge pins slightly larger diameter than the damper wire with some water alcohol for sizing.

I use Bill Spurlock's method with alcohol and bridge pins. Just scroll down to section 3 and it is explained. The whole article is good read FWIW...

http://www.rennerusa.com/PDF/flange-bushing.pdf

Insert #6 bridge pins and saturate with VS Profelt, or a mixture of alcohol and water. Make sure you polish the damper wires before you re-install the dampers.

Use an upright damper blade, heat the wire, and burnish the felt .

Then lube with talcuum .

Traditional method but the alcohol/water sizing is good, while less predicteable, as it shrink the cloth.

It may work less with a cloth mixed with synthetic fabrics.

Very little easing may be necessary once the glue have set (with a big pin in the hole yet while drying)

Also, burnishing is necessary for those cloth, you can iron them prior to gluing too.

Be careful not to harden the cloth with the glue. Yes the Spurlock instructions are very good,as usual

I keep a piece of ancient umbrella wire stuck into a handle that is precisely the half round size for doing this job quickly without disassembling anything.

It has to be from the inner stems of an umbrella made some 20-30 yrs ago. Modern umbrellas are made of square stock and won't work for this so you'll have to check your attic.

The first 2" or so are smooth for burnishing and then, further down, I have roughened the surface for stubborn cases.

Saves hours.

I have found old umbrellas in many countries that are the right size. The one I use now I made from one I found in a trashcan on a stormy day in Virginia. I made a few out of it and gave them to my colleagues.

HA,, the umbrella !!! nice tip, it may be very smooth, once I had lost a bushing with an unadapted one (was made of whale teeth possibly ;))

The return of corset in fashion will help the piano technicians !

Ah. Yes. Thanks for reminding me, I did thin and round the insertion point. The need for this would become readily apparent on the first attempt at use. Yes, corset steels or a length of thin whalebone made the best soundboard cleaners. Lots of ladies walking around lopsided in those days.

I like Isaac's method of using heat. Heat irons the felt, and makes for more consistent sizing. I made an tool with a soldering iron. It's a bridge pin inserted into a piece of brass rod. Then the brass is big enough to tighten in the end of the soldering iron. I always finish up with this, as it seems like a more permanent fit. The level of heat is controlled with a rheostat.

The umbrella wire seems good to carry around out in the field. Not as bulky as a soldering iron.

This is a must, I was happy to find a specific rheostat for irons (up to 500W) Never seen them sold elsewhere it is simply sending voltage trains at a more or less frequent speed, but the process make the heat to stay stable (for some reason explained by the maker)
The standard rheostat that can be used on light bulbs break in less than a year if used to regulate an iron

Too much glue in the budhing cloths is to be avoid because the cloth will wear faster when hardened with the glue, even if it is only on 1/2 of its thickness.

Hide glue is very advantageous for that as you can allow it to gel a hair before gluing so the cloth is preserved.

I like the speed we gain when using PVC for gluing bushing cloths, but a lot of care have to be taken not to allow the glue to enter the cloth.

It counts in years of use when key bushings are concerned.

You usually don't have to use glue to hold the damper guide rail bushings in place.

depends of the shape of the hole(possibly), both versions exist

with a thin flat plank I belmieve they are glued, and with a thicker one and a conical shape on the underside, may be not.

may be irrelevant, SUzan Kline should have stated that very well...

Just make sure to chamfer the holes top and bottom (making an hourglass cross-section) and no glue is necessary.

- Mark