Pinblocks and o/s pins

[Farrell]

Or, what really works like a new pinblock, is to epoxy in 1/2" pinblock plugs, and drill for appropriate size pin. That way you are back to 2/0 or whatever pins, have new pinblock material, and all holes are of similar characteristics - works just like a new pinblock. It really is not hard to do. IMHO, a better way to go, if not replacing pinblock.

Terry Farrell
  
----- Original Message ----- 
From: "Bill Ballard" <yardbird@pop.vermontel.net>
To: <pianotech@ptg.org>
Sent: Sunday, May 12, 2002 1:30 PM
Subject: Re: Pinblocks and o/s pins


> At 10:03 AM -0700 5/12/02, David Love wrote:
> >When stringing a piano with oversize pins.   What method do people 
> >use to prepare the old block.  I've >been reaming with the gun 
> >cleaning stiff bristled brushes, but I wonder if there isn't a 
> >better and more >consistent way to get to fresh wood.
> 
> That's the best that I can do, to slough the dead wood off the tuning 
> pin hole walls with a gun bore brush. What with far more turning in 
> the middle sections, and the bass undergoing far more prying forces 
> due to the thicker plate web, I wouldn't expect to find consistent 
> wear on the tuning pins holes, across the block. On a block needing 
> oversized pins, it frequently takes a 4/0 pin in the middle to feel 
> identical to an original 2/0 up in the top treble of the block. So it 
> would take 10 mils of stock removal to equalize the pin torque 
> between these two holes. And that's not answering the question of 
> how that 10 mils should be tapered down from the loose pin hole in 
> the middle to the tight one in the treble. So consider adding 5 mils 
> to the stock removal and increasing the pin size to 5/0.
> 
> So you've got the entire set of holes re-bored (hopefully) at .296". 
> Given that the original difference between bore and pin diameter 
> might be anywhere from .031" to ".020" (a .281" pin in a hole bored 
> at either .250' or .261"), what size pin would be needed for this 
> re-bored hole, .265" or .276"? Remember, you just pulled a .281" pin 
> out of there which was a loose enough fit to require some sort of 
> repair, suggesting that the hole size might not be more than a few 
> mils down from .281".
> 
> Re-boring to get fresh wood is another matter entirely. Were we 
> supposed to do this with a hand drill? The one person I knew who did 
> this successfully was going .250" into marine plywood. The tolerances 
> in re-boring are far more critical. So much so to require re-boring 
> with a drill press. Unless the pinblock can just be lifted out of the 
> rim, it will require an "on-the-piano" drill press. Several good ones 
> have been described recently: one in the Journal within the last 
> year, and Terry Farrell's overhead version.
> 
> Oversized pins in the original block always contains an unknowable 
> risk: how is the pin size going to feel immediately after stringing, 
> and five years hence. I'd judge the block by how good or 3/0 placed 
> in a weak spot feels. The lousier it feels, the greater the 
> inconsistency you're going to ask the procedure (brushing/boring) to 
> overcome.
> 
> Maybe Epoxy reinforcement is a viable technique here, but even the 
> one paper I've read on it (from Epoxy Technology, the report of an 
> antique piano conservator) described it as plugging the tuning pins 
> holes and then re-boring (for 4/0 pins when replacing 2/0s).
> 
> Bill Ballard RPT
> NH Chapter, P.T.G.
> 
> "There are fifty ways to screw up on this job. If you can think of 
> twenty of them, you're a genius......and you aint no genius"
>      ...........Mickey Rourke to William Hurt, in "Body Heat", discussing arson.
> +++++++++++++++++++++