Hi Joyce,  I have replaced many of the old roller skate wheel and cast
iron casters on way too many old pianos.  I use the tilting shop dolly
to do it, and as a precaution, if I'm working alone, (as is usually the
case) I strap the dolly to the piano with a good wide ratchet strap.

The reason for this measure is to prevent the piano from rolling freely
on the new casters as I'm standing it back up in my shop on the cement
floor.  When that happens the piano lands on its back with a horrible
crash!  If you're doing the work on carpeting, it's not as likely to
happen.

I order new casters from Schaff for replacement.  If you are putting on
the dual wheel style, you need to expand the well the casters go in so
they'll rotate 360 degrees; otherwise, with the single wheel casters,
it's not necessary.

Dan Armstrong - Armstrong Piano Tuning & Repair
Pine River, Minnesota