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Need help with bridge placement new P-Bass

Discussion in 'Luthier's Corner' started by brainhertz, Feb 21, 2004.

  1. brainhertz


    Feb 21, 2004
    I'm about to build a P-bass and the one thing I'm having trouble finding is detailed information about placing the bridge since I bought a Mighty Mite body without the bridge holes predrilled. Since bridge placement is so crucial I want to make sure I get it right. Can anyone here walk me through it step by step?
  2. Skips


    Feb 19, 2003
    I've never done it, but, I'd assume that you just measure it so that the saddles are (when in the center posistion) 34" inches from the nut (on a 34" bass), or slightly farther, as the heavier strings will need to be slightly farther to adjust for Compensation (I think that's the right term...it has to do with the fact that you bend a string slightly when you fret it.) I Just measured my bass, and it's 34.4" for the B and 34 for the G. But you don't have to be too exact, since your saddles should move enough to work it out.
  3. RobbieK


    Jun 14, 2003
    Wind the saddles out to the end of the tailpiece and then back a little, suss out where the string's witness point on the saddles is, and use this point for your reference - you'll only need to wind them in the direction away from the neck when you are setting up your new axe. Bolt the neck up, and use a straight-edge to get the centre line on the body. Even if your body has a bookmatched top, don't take the glue seam as a true centre line. If you have one, use a drillpress for the holes. Just to make sure, measure from the front edge of the nut to the middle of the 12th fret. This is half scale. Should be 17 inches/432mm, but some basses actually have a 860mm scale....

    best of luck!
  4. That last bit should read: "Just to make sure, measure from the center of the saddle to the middle of the 12th fret."

    BTW, to "suss out" the witness point means to measure from the 12th fret towards the bridge location. On your bass, that measurement will be 17" or exactly half of the full scale length of 34". That locates the "witness point" or the point at which the string stops vibrating - as it breaks over the saddle.

    Robbie is right in that once the bridge is in position and strung up, you'll only be moving the saddles to the rear for proper intonation.

    Here's the method for finding the centerline of your neck (just expanding on Robbie's tip):

    Bolt the neck to the body. Take some masking tape and run a strip from alongside the neck back to the heel of the body on both sides and one strip directly down the center of the body. These are so you can make visible marks on the body without damaging it. Now, using a long straight edge, lay it alongside the neck against the edge and draw a line down the body (on the tape!!) on both sides of the neck. What you'll have is a pair of converging lines that get further apart as they near the rear of the body. You are essentially extending the taper of the neck all the way to the end. When that's done, pick a point near the neck and measure the space betweent these lines and mark the exact center (on the centerline tape!). Then move towards the bridge and do the same thing. Choose two points that are spaced well because this will increase your accuracy. Once you've got the two points marked for center, draw a line connecting the dots and you've created a centerline to your NECK and that's the important one.

    Hope this helps
  5. brainhertz


    Feb 21, 2004
    Thanks for all the info. With these instructions I'm sure to get it right. FYI, I got a chance to take measurements on a P-bass last night and found that with a standard Fender bridge (L-shaped bent metal variety) that the distance from the nut to the center of the mounting screws was 35" and that the center of the center mounting screw was aligned perfectly with the center of the fingerboard, using the dots as a guide. I've bought a drill press for this project. Now all I need to do is find my roll of masking tape and I think I'll be ready to roll. I have another question about drilling. Should I use brad point bits or would standard drill bits be OK?
  6. Standard is fine.

    I find it funny that you don't have a lot of experience yet you inquire about brad point bits! Bravo!
  7. RobbieK


    Jun 14, 2003
    Hambone I meant the front edge of the nut (the bone or plastic thing near the headstock with the string grooves). I have come across a few necks that look like 34" scale, but are in fact slightly less (860m). So by measuring the half scale on the neck, you can just make sure.

    By the "string's witness point" I mean, literally where the string is gonna start vibrating at the saddle. (For a fender type barrel saddle, for example, about the middle of the upper side).

    As for the centre line, don't always take the centre of the dot inlays to be right on the centre. (Some necks have dots that are surprising inaccurate.)

    I'm no goemetry guru, Hambone, but I'm not sure that your method of finding the centre line is the most accurate, unless you know the angle at which to place your ruler to measure between the convergent lines, across the body. It won't be 90 degrees because the lines are not parallel. IOW, unless the angle the ruler makes with the two lines you've marked is the same on both sides, the half way point won't be on the centre line. I usually grab the neck and measure across the frets in a few places, mark the centre (on bits of masking tape), then tape a metre rule down the centre line. Of course, with the neck bolted up, the ruler will be off the body by a bit, but you can sight and mark points on the center line with a squared block or something. Or simply slide the bridge under the ruler and mark the holes directly.

    hope this makes sense...

    (sometimes my Australian accent can confuse people) ;)

  8. If you pick 2 points on the measuring tape - say 2" and 5" - then put the 2" mark on the left line and the 5" mark on the right line, precisely mind you, the 3½" mark is exactly the center between the lines. Yes, you are correct the lines would have to be parallel to work with a diagonal but this is a very accurate method as is.

    Measuring across the frets could be a dubious method in my mind. Slightly different fret lengths, uneven fret dressing on each side, or an imperfectly relieved fretboard edge could throw the measurement off. And, like you mentioned, the dots are definitely off limits for a decent measurement