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Bridge positioning method?

Discussion in 'Luthier's Corner' started by bholder, Dec 25, 2014.

  1. Dec 25, 2014 #1
    bholder

    bholder Affable Sociopath Gold Supporting Member Supporting Member

    Sep 2, 2001
    Vestal, NY
    Received a gift from Sire* (see sig)
    So I'm an amateur builder working on some projects where I'll need to determine the proper bridge position on blank bodies. Any good "rules of thumb" for doing this? Just measure the scale length from the nut, and place the bridge so the saddles are in the middle of their travel on that line?
     
  2. Dec 25, 2014 #2
    Andii Syckz

    Andii Syckz

    Jan 2, 2011
    Montreal
    Rule of thumb: measure out from the nut to the 12th fret, and multiply by 2. You'll have your scale length. then you put the g string saddle at just a little over half it's travel, and position the bridge to that it's centred with the centre line of the body (assuming you have drawn a line down the middle of the blank).
     
  3. Dec 25, 2014 #3
    bholder

    bholder Affable Sociopath Gold Supporting Member Supporting Member

    Sep 2, 2001
    Vestal, NY
    Received a gift from Sire* (see sig)
    Yeah, that was about what I was thinking, with the G string, so that the rest have adequate room to go further back. I did find a bridge positioning calculator online, but you have to know things like the weight per inch of the strings and so on, takes a while to figure that out, but I'll work through it as a cross-check. (That site is designed for a single diagonal bridge saddle, as in an acoustic, but should be very close to the actual bridge saddle positions with a metal bridge, if I plug in the right numbers for the strings.)
     
  4. Dec 25, 2014 #4
    Bruce Johnson

    Bruce Johnson Gold Supporting Member Commercial User

    Feb 4, 2011
    Fillmore, CA
    Professional Luthier
    First, attach the neck to the body. Make sure it's seated correctly in the pocket and locked down.

    Lay a 36" straightedge along the side of the neck, against the edge of the fingerboard, and laying across the body. Draw a line on the body back in the bridge area. Do the same on the other side of the neck. The bridge must be centered between those two lines. The pickups should be too, if you are doing any pickup routing.

    Verify your scale length by measuring from the fingerboard-side of the nut to the center of the 12th fret. Your scale length is exactly twice that. Measure that same distance, 1/2 the scale length, from the 12th fret back onto the body and make a mark. That's what we call the Zero Line.

    Now, adjust the bridge's saddles until they are almost at the front limit of their travel. With the saddles at that position, the bridge should be mounted with the saddle witness points right on the Zero Line. To get proper intonation, the saddles need to be able to be moved back from the Zero Line 1/8" to 3/8". The saddles will never be moved forward of the Zero Line.

    To get the bridge square, first spot, drill and screw the bridge down with just one center screw. Then take your time lining it up to make sure it looks right from across the room. Or you can measure from the back corners of the bridge to, say, the ends of the 12th fret. Get it right. Then spot, drill and install the outboard screws.
     
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  5. Dec 25, 2014 #5
    bholder

    bholder Affable Sociopath Gold Supporting Member Supporting Member

    Sep 2, 2001
    Vestal, NY
    Received a gift from Sire* (see sig)
    Thanks, good stuff!:thumbsup:
     
  6. Dec 25, 2014 #6
    bholder

    bholder Affable Sociopath Gold Supporting Member Supporting Member

    Sep 2, 2001
    Vestal, NY
    Received a gift from Sire* (see sig)
    The first project I'm getting back to has a nice center line in the top veneer, and bridge screw holes from the original bridge, so lining up and getting square should be easy enough - but I don't have the original bridge, no idea what the distances from those screw holes to the original bridge's saddle travel was. Good to go, now, just waiting on parts (making a "frankenSchecter"). :)
     
  7. Dec 25, 2014 #7
    Bruce Johnson

    Bruce Johnson Gold Supporting Member Commercial User

    Feb 4, 2011
    Fillmore, CA
    Professional Luthier
    Yeah, but still check it all very carefully. In particular, make sure the neck lines up with the center line in the veneer, before you start drilling holes. Do the layout with the straightedges to verify that.
     
  8. Dec 25, 2014 #8
    bholder

    bholder Affable Sociopath Gold Supporting Member Supporting Member

    Sep 2, 2001
    Vestal, NY
    Received a gift from Sire* (see sig)
    Thanks for the advice, will do. I'll get it all laid out in pencil and triple checked before I start drilling. :) Not even sure yet whether the old screw holes will be covered by the new bridge, but they're in 2 rows, so probably, I'm hoping. Should the old holes be filled with dowels and made flush? I mean, of course, if the old & new overlap and aren't aligned, but otherwise?