just what is 7/32"?

[Carl Meyer]

Great question.

I have both taps for agraffes.  7/32 and 1/4 inch, both are 36 threads per
inch.

My machinists chart lists drill # 7 for 1/4-20 and drill # 3 for 1/4-28 or
32.
It doesn't list 36 threads per inch at all.  I think I would start with
drill # 3 and try to thread the holes with the 1/4-36 tap lubricated with
you favorite brew.
There are tapping and threading compounds available which are probably
expensive, repackaged light oils.  A slight countersink may be advisable to
make sure the threads do not bind if the agraffe hasn't been threaded all
the way to the bottom.  If the threading is difficult use a slightly larger
drill.  Finer threads are not as strong, but are used since it allows easier
adjustment to align the agraffes to the strings.

If someone has a chart listing 1/4-36 tap drill size I'd be interested to
know what it is.

Thanks

Carl Meyer




----- Original Message -----
From: Clark A Sprague <clarks11628@juno.com>
To: <pianotech@ptg.org>
Sent: Friday, April 20, 2001 5:49 PM
Subject: Re: just what is 7/32"?


>
> On Fri, 20 Apr 2001 18:49:07 EDT Yardarm103669107@AOL.COM writes:
> > In a message dated 4/20/2001 11:39:52 AM Central Daylight Time,
> > A440A@AOL.COM
> > writes:
> >
> > << Nossman suggests threading out to 1/4".  I have a natural
> > reluctance to
> >  begin machining on my only plate for this piano >>
> >
> > Ed:
> > I've done this twice, and it's easier than you think and very
> > non-threatening. Cast iron taps very easily and pretty cleanly,
> > certainly
> > more uniformly than the situation you have now.
> > PR-J
>
> Paul,  would you drill out the old holes first, and if so, what size
> drill?  (before tapping-out to fit 1/4" agraffes?)
> Clark Sprague
> Detroit/Windsor Chapter
> >