Bridge Pin Offset

[Farrell]

Hello Ron Overs - or anyone else that cares to chime in - in your.....not-so-recent post below, you indicate that you use 10 degrees of string offset (between front and back rows of bridge pins), and a 20 degree pin inclination.

I was laying in bed this morning trying to work through the process of punching some holes in a bridge top (well, actually, the process of locating the holes). Now I can do a pretty good job of copying a pattern off an old bridge and transferring it to a new one - I can even straighten things out a little bit. But one should be able to start from scratch and get a straight line from the tuning pin, under the capo, down the speaking length, get the targeted offset angles across the bridge and come out with a wire oriented parrallel to the speaking length on its way to the hitch pin.

It sounds simple enough, but when you actually get down to it, it appears difficult to do with precision. Many take the course of marking the bridge top with two dots along a straight line from the capo/agraffe to the hitch pin. While that may be "good enough" in many cases, I would feel more comfortable having complete control over this process.

There are several factors that will conspire to make this process a less-than-straightforward one: varying string diameter, bridge pin angle (and resultant string position away from bridge pin hole in bridge top), distance between forward and aft bridge pins, hitch pin position, and softness of bridge cap (I suppose we are using maple/boxwood/whatever hard enough to not worry about this?).

Do you have a methodical approach for locating new bridge pin holes that result in the desired 10 degrees of string offset? Thanks.

Terry Farrell
  
----- Original Message ----- 
From: "Overs Pianos" <sec@overspianos.com.au>
To: <mfarrel2@tampabay.rr.com>
Sent: Sunday, September 10, 2000 7:52 AM
Subject: Re: False Beats


> Terry,
> 
> >Very interesting experiment. Your "string offset angle which is often below
> >10 degrees" - the string offset being the angle that the string makes as it
> >goes from the speaking length and bends around the first bridge pin? And
> >that angle being controlled by the placement of the rear bridge pin. Am I
> >right? Just making sure. Thanks
> 
> Sorry for the delay in getting  back to you and the list. I got a bit 
> tied up with work towards the end of the thread, which caused me not 
> to catch up with some of the latest contributions.
> 
> I decided to answer you personally since the topic has since faded 
> from discussion.
> 
> The answer to your question is yes. However, we don't use angles of 
> less than 10 degrees of string offset. The matter I referred to was a 
> piano where the offsets were incorrectly calculated.  We use ten 
> degrees of string offset, combined with a bridge pin inclination of 
> 20 degrees off the vertical.
> 
> Hope this helps,
> 
> Regards,
> 
> Ron Overs
> -- 
> 
> _________________________
> 
> Website:  www.overspianos.com.au
> Email:      ron@overspianos.com.au
> _________________________
>