<html> <blockquote type=cite class=cite cite> Roger, I do not understand your abbreviation "spec'ed", but your sentence seems to imply Hamilton was made to use only Darnell type casters unless someone was trying to save some money. </blockquote> Hi Kieth,                 The specifications call for Darnell castors, from time to time there has been substitutes for what ever reason.  I assume it was penny pinching. and they gave problems. The spec's also call for a force fit.  Things go wrong in the plant, and  I have seen times when little short screws were used, and that also lead to problems. I would agree that the Hamilon's (45" studio piano) have not had so many problems with castors. <blockquote type=cite class=cite cite>I have yet to do caster work on any Hamilton Studio piano in 23 years that ever used Darnell castors, only the university style casters I referenced in an earlier post. To support this I have at least 40 Hamilton Studios and another 67 Baldwin Studios in my dbase, many of which I service annually.</blockquote> As for Hamilton's, we have been selling about 40 a year (on average) for the last 30yrs, so I think I have you beat for numbers dept. Where they are rolled over surfaces that go from solid to carpet, that is where the problems start.   Those carpet cleats play havoc with them. But to be fair, I don't think any caste r mount,will stand that for long. Regards Roger </html>