I, too, ruin my fingers when I put on leather nuts.  I use a screw
starter to begin the threads or sometimes drill out the hole for larger
rods.  I have used Durrell Armstrong's plastic nuts once or twice
decades ago but found that they not only self "lock" but they lock
firmly enough to break the metal poppet wires when you try to readjust.

Most of my experience with them has been removing them from rebuilt
players from other rebuilders in the past.  One or two of them were
only "rebuilt" a few years ago.  These red-brown nuts must be cut off
or you will twist off the threaded ends of the poppets.  This fact has
made me never use them again.  The leather nuts tend to corrode, but it
takes years for this to happen.

I would be interested in the nylon nuts but I wonder how tight they
will become in future.  Their not corroding or rusting my beautifully
wire-wheeled and lacquered poppet wires would be a definite plus.
I always buy leather nuts by the thousands.  I go through quite a few
some years.

One other comment on the posting:  What is wrong with replacing felt
with felt?  For control rods I use keyboard center rail punchings or
hitch pin or butt spring punchings depending on what was there
originally.

Tips on leather nuts and saving fingers:

When putting nuts on a set of poppets, use your cordless or variable
speed drill on slow.  I have a Makita cordless drill with a finger
tightening chuck.  You may chuck up the straight wires into the drill
and start slowly.  Once it's on you can go to fast but do not strip it
out when it goes to the correct spot next to the chuck.

If there is a hook at the end you can chuck up the nut itself or you
can leave the chuck mostly open and fit the hook into the chuck loosely
and crank on the nuts that way.  You will have the wires out since you
will surely want to rebush the wood fingers with new felt, right?

D.L. Bullock    St. Louis
http://www.thepianoworld.com/