[pianotech] composite pinblock- Drill bit size

[Ron Nossaman]

On 9/23/2010 9:45 AM, David Renaud wrote:
> Thanks for the advise, and yes perhaps next time I will buy or make make one as per the suggestions. I do have 2 more Boesendorfer blocks to do.....
>
>     But....I have already made and fit this block, done.
>     It is 3/8 delignite over 1.5 inch bolduc block.
>
>     Was hoping on thoughts on drilling for this particular thing
> actually laying in front of me. Bolduc's drill bit reads .255.
> Lots of give in the maple...not so much in the 3/8 delignite top.
> Perhaps a very tight collar at the top will feel good, perhaps I
> should redrill the top 3/8 with a second pass and a bit correct
> for the delignite.....
>    I have extra material and will make up a sample the
> experiment with, but some of you have been here before and
> have opinions on this...


My system's been down, so I'm trying to catch up a little here.

The point of the hybrid block is to have the pin tighter and firmer in 
the dense top layer than in the softer bottom layer. Like with bridge 
caps, the top does most of the work. Making the bottom of the pin as 
tight a fit as the top defeats the friction gradient that makes these 
things tune so nicely. Do that, and you'd just as well be using Delignit 
blocks in the first place.

My 6.8mm final drill size is dependent on two preexisting conditions. 
The first is the Delignit density and thickness (It's pinblock 
equivalent, 9mm. I don't like the bridge capping stock. Too soft), and 
the main block density and hardness (I use the multi-lam). The second, 
and this is critical, is two pass drilling. You will get a consistently 
tighter and more uniform fit drilling in two passes than you will with 
anything you can come up with for a single pass.

So with the block you have, as with any block, make some test holes and 
learn how to get what you want from what you have and are willing to 
use. That advice never changes, as asking someone for specifics on 
something different from what they do won't get you dependable information.

And I still use Denros with no problems at all.
Ron N