Bridge caps

[Ron Nossaman]

Good questions, I've wondered about these things too. I don't have answers,
but I have thoughts... as follows.

>1) I have noticed a large amount of variation regarding the string contact 
>area on the top of bridges.  I am not one to slavishly repeat a manufacture's 
>or a factory worker's poor design or poor execution. So I have often wondered 
>but never found an answer; what is, if the is any, the optimal amount of 
>contact surface?

I've seen as narrow as 10mm, up to ??? way out there. The 10mm thing was at
the treble break where the laminated bridge had insufficient dogleg to
allow the pin pattern to stay centered. The back row was relocated to keep
the pins on the bridge. Generally, I think, the pin rows should be far
enough away from the edge for adequate support, and far enough apart from
each other that the stagger angle is controllable. The closer together the
rows are, the less margin for error you have drilling the holes, and the
more the angle lessens as the bridge ages and the pins migrate from the
string tension. Bridge angle is figured in too. In the high treble, the
strings are nearly perpendicular to the bridge. In the low tenor, they are
more nearly parallel. This decreased crossing angle makes the effective
bridge width considerably wider down there. Low tenor pin spacing tends to
be wider accordingly. I don't know if there is a real difference in
termination quality as a result, but you certainly don't have to carve out
most of the cap in long notches if the spacing is adjusted accordingly.  


>2) A corollary would be should this contact surface be centered on the cap?  
>I have seen them all over the place with various degrees of splitting in all 
>cases.

No, but the cap should be centered under the contact surface, since the
bridge is (supposedly) built to accommodate the scale. The only reason I
can logically justify for centering is to get as much pin support as the
bridge width allows. Acoustically, I can't see how it could make a
difference one way or another except in the high treble, where the pin rows
are often off center forward to get the bridge footprint as far from the
belly rail as possible.


>3) Do we really need to grind off the tops of the pins for anything other 
>than an even appearance?  Those buggers get sharp, I know, I have the scares 
>to prove it.
>Andrew Remillard

Me too, so I quit doing it. This became "The Way It's Done", I think,
because Steinway did it. They did it because they hand drilled the holes,
and couldn't control the depth all that accurately. As a manufacturing
expedient, they just drilled the holes a little on the shallow side so the
pins could be driven in until they bottomed out (eliminating the need to
pay attention to final height), and filed down after the fact to make them
uniform. 

That's the tip of the iceberg, I know, but that's the short version.
Bridges don't seem to be any better understood by most folks that are
soundboards, which is why I'm going to attempt a class this summer in Reno.
Meanwhile, I'd like to see all the rational discussion I could get on the
subject. I can always use more ammunition.


Ron N