Machine Threads in Pinblock, was WD-40, now plate screws!

[Paul Chick]

Hi Terry:

 

This is ever so slightly off topic at hand, but I’ll run with it anyway.
I’m going to be using the 3/8” x 16 thread x 4” long socket set screws for
plate screws as you, Ron, Del, and others are doing.  What size drill bit
are you using to drill the hole in the rim? (or drill the plugs glued  in
the holes, as it were).  Are you tapping afterwards?  What size tap if so?

 

I was able to get these screws, acorn nuts, etc at my local Fastenal.  One
inch round brass stock as well for mass loading.  I mention this for others,
as there are supposedly 4000 of these stores in the

 U. S., so you may just be able to run down the street instead of mail
ordering.   Lots of other stuff there that us weird piano rebuilders might
use or adapt, and they have a huge catalog.  

 

Also, these 3/8” screws miked out at .369 instead of the .375 that 3/8”
works out to.  Does that differ from your stock?

 

Thanks for your help!

 

Will Truitt

 

By the way, I think this set up is absolutely brilliant in its simplicity
and application.  Kudos to Del and Ron for coming up with it.

 

Hi Ron!  I also use coarse thread as you do. However, I have tried tapping
the maple and found that it made the hole too big - I used the proper tap
for the given machine screw. I figured that the maple must have enough give
in it (compared to metal), that caused the poor fit. I've gone to simply
drilling a hole a little smaller than the thread and simply running a
buttered (wax) machine screw into the hole (just like one does with a wood
screw). I seem to get the nice tight fit that way. Do you find that you
machine screw have a snug fit after tapping the hole?

 

Terry Farrell

Fenton,

 

. . . Would you recommend a fine or coarse thread?

 

Always course threads in wood. We use the regular tapping tools after
drilling the minor diameter.

Ron O.

 

You can make a “tap” from the threaded rod you intend to use: drill your
minor diameter holes as planned.  Put about a 45 degree angle on the end of
a piece of the threaded rod just enough to be less than the minor diameter
hole to form a lead on your rod just like the lead on a machined tap.
Looking at the rod from the end: visualize the end to be divided into
quarters with an “X” that gives you  a north-south, east- west
configuration.  Grind a trough in two opposite quarters with one edge
parallel to the north-south line, and the other edge parallel to the
east-west line.  A square edge on a grinding wheel does a tidy job.  The
trough must be deeper the minor diameter of the thread and taper to
infinity, about ½” long.  Put a suitable handle on the other end, and “tap”
your holes. This also works great for chasing damaged threads.  Your
threaded rod will fit better than using a machined tap.

Paul C

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