clean - don't ream!

[david c. brown]

>"Clean - don't Ream" was the title of a technical done at a long-ago seminar
>by Wendell Eaton and ? (I forget who).  Their premise was that cleaning
>tuning pin holes with a rifle cleaning brush chucked up in a drill was a
>better way to approach the repinning problem than reaming the holes.
>
>I've been less than happy with some of the repinning work I've done over the
>years......none have been underpinned, but there have been some jumpers and
>a lot of supertight pins,  particularly where I've not done anything at all
>to clean or ream the holes.
>
>Now I have to repin the bass on a Steinway "O".  It's never been touched,
>and  a few of the pins wouldn't hold at all, so I tapped them very lightly
>just to hold them for a week till I get down to work.
>
>As I consider reaming the holes, I checked in the Schaff and Apsco
>catalogues for reamer specs, and I note that the tolerances between
>recommended reamer size and pin size are not the same for both suppliers:
>(Pianotek's reamers come in assorted sizes, but no pin sizes are mentioned
>in the book).
>
>For 3/0 pins (nominally .286) Schaff suggests a .276 reamer, while Apsco
>lists a .280 reamer.
>
>For 4/0 pins (nominally .281) Schaff's reamer is .291 and Apsco's is .285.
>
>I know from drilling new pinblocks that there is a hell of a difference in
>torque between  holes drilled at  .010 tolerance and those at .006
>tolerance.
>
>So what's the advice of the list on this?  Should I ream, clean, or just
>plug 'em in? (I'd be using 4/0 in the bass, probably.  And if reaming is
>best, what size reamer should I use?
>
>Rob Stuart-Vail


Rob and List-

This is an excellent topic that I tried to engender some discussion on a
few months ago. Figuring pin sizes in an existing block is more of a crap
shoot than in new. Here's my 2 cents worth.

First I would not recommend chucking a gun brush in a drill to clean holes.
I have done that on one pin as an experiment, and the amount of  dust on
the keybed and the resulting  low low torque levels prompted me to instead
tightly secure a brush in a heavy T handle and go at it by hand. The first
few holes require a bit of effort, but things soon smooth out. Use several
brushes throughout as the do loose their bite pretty quickly.  If I get to
an area that I feel is too tight during stringing I will brush again.
Remember too that you may be driving these pins deeper after initial
stringing to even their level. What is OK at first can quickly become too
tight a few mm deeper in the block.

Prior to this I would take careful torque measurements and see just what
size pin you would need. I am finding on our pianos here at school that
sometimes a 2 size jump is too much. Given that they are newer pianos,
sometimes with many string replacements in the capo, getting even torque
can be difficult. I am beginning experiments w/ spoon reamers, again in a T
handle to try for more even torque. I think that the more reamer sizes you
have, the greater control you can get. Don't be so concerned with what
supply house says is the correct size. Machinist's supply stores are a good
source for these items as well.\

Hope this helps-


It's your attitude
Not your aptitude
That gives you
Altitude


David C. Brown RPT
School of Music
The University of Texas at Austin
dcbrown@mail.utexas.edu