<html> <body> Tom & friends, I have devoted an unconscionable number of hours to this pursuit, to no avail.  The screw dimensions are .2125" (5.4mm) iameter and 28+ tpi.  There must be someone who knows the history of this screw, why these dimensions were employed and when it might have changed.  At this point it seems a matter useless curiosity, nothing more.  Thanks David Skolnik Hastings on Hudson, NY At 12:03 PM 7/22/2008, you wrote: <blockquote type=cite class=cite cite="">Hi, David I. and David S., and Colleagues -   I took a look at the pedal plate on an 1889 Steinway, the oldest on the premises at the moment.  (I figured if there were an oddball thread to be found it would be more likely the older the piano.)  I found that screws anchoring the pivot rod were garden-variety No. 8 32-thread x 1/2 inch flat head machine screws.  We have a box of these screws we keep on hand for the occasional replacement.   To David S.:  30-thread would be very odd indeed.  There is no current or recent (20th century) American, Canadian or British standard thread at 30 pitch.  And that's why many thread guages skip that pitch.  Metric threads don't quite approximate that either.  I accidentally deleted your post on the topic, but I recall you mentioned measuring your screw diameter at something like 0.213 inch.  That would be about right for a No. 12 screw, which should be 28 pitch in the fine-thread series.   There would be no point in S&S using special threads for this part.  Common hardware is available to do the job and it would be much more expensive to have custom-made screws and custom-made taps, etc.   ~ Tom McNeil ~ Vermont Piano Restorations VermontPiano.com</blockquote></body> </html>