[pianotech] Taps from the other side

[Ron Nossaman]

On 8/17/2012 1:01 AM, John Ross wrote:
> What is the size of the screws that goes in brass flanges?
> When the brass plate breaks the screw does not fit the replacement
> plate, from Schaff.
> The screw that  is supplied with the new plate is too long, and the
> round head isn't right.
> What tap do I need?

I don't know, John. It's either a #3, or 2.5mm, and I don't have a 
thread gauge that goes down that fine, so I can't measure the thread 
even if I could see the thing. They sure are different threads though, 
even though the same diameter. A tap wouldn't help anyway, as you likely 
wouldn't end up with enough thread in the plate to do any good. Can't 
help with the head, but you could screw the new screw into the new plate 
with a tad sticking out the other side and file or grind it down to 
length. Shouldn't be necessary, but there are a lot of things in that 
category.


> I seem to have trouble trying to figure out the size.

So does Schaff, who has a long history of thread confusion. Some of the 
folks out there might remember their 9/32x36 double helix thread 
oversize agraffe replacement that wouldn't go into any threaded hole on 
the planet including one threaded with the tap they sold for them. They 
never did understand that the threads needed to have been single helix 
to work, and sold those things at great expense in time and frustration 
(not to mention damage) to their customers, for twenty years that I know 
of. I finally bought the last of them just to get them out of circulation.
Ron N