[CAUT] steinway pedal plate screws

[David Skolnik]

Tom -
I don't know which I find more insulting: that you deleted my post or 
that the South Bend Precision intentionally excluded my size screw 
from their machine.  humph!  So, I could resend you my post, but as 
Jon Page would tell you, you can check the archives. (you don't 
really need either)

I assumed, and still do, that the original question referred to the 
round head pedal plate screw, not the one's you mentioned in your 
opening paragraph, though that's useful info.

I decided to remeasure today, since I was still coming off one of my 
regular summertime binges and my eyes were having trouble 
focusing.   I was guesstimating because that's the jump on my leaf 
gauge, and it seemed to be somewhere in between.  Here's what I'm 
seeing now, with the un-Lasiked, myopic 60 or so year old eye:  Over 
the interval of 4 gauge teeth on the 28tpi leaf, the gauge teeth go 
from bearing against  the 'front' peak to bearing against the 'rear' 
peak.  As I try to place more of the entire quage on the full length 
of the screw, any semblance of congruency fails.  So what could that be?  28.5?

As far as whether Steinway made custom screws, I hope someone with 
more knowledge can speak up.  I know that there are sizes, certainly 
in wood screws, that were standardly available at that time, though 
no longer.  As I told David I., look at the old keystop rail prop 
pins & nuts, or the old action rail screws.


At 12:03 PM 7/22/2008, Tom wrote:
>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.
>
>Sidebar:  I have a very nice South Bend Precision Lathe that cuts 48 
>different thread pitches.  Conspicuously absent from that list is 30-pitch.
>
>Another Sidebar:  It is not desirable to set these screws "gorilla 
>tight".  Notice that the pivot rod makes contact with the screw very 
>much off center from the axis of the screw.  Using a screw this way 
>would be considered abusive in some circles; it will cause the screw 
>to break well below the tension needed to break a screw with 
>concentric loading.  However, tightening the screw moderately snug 
>is more than adequate to hold the pivot rod.  It's another example 
>of an elegant mechanical design from S&S!!

Are you being sassy?

Regards

David Skolnik
Hastings on Hudson, NY


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