Intonation and bridge details.

Posted by D.C. Mansfield on February 3, 2011 at 2:55pm

 Hi all,

         I'm just making my second guitar, and I could do with some help to clear up a point that I don't understand.

On 6 string (and most 'proper') guitars, I've noticed the bridge isn't straight, and at a 90 degree parallel to the strings, but is set at an angle, so the lighter stings have a slightly shorter length.

  I was wondering why this is, and if it's necessary on a 3 string guitar?  If so, how do I calculate the angle of the bridge?

  My bridge design is a threaded bolt recessed into a oak base.

  Thanks all.

 - Duncan.

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Replies

  • mike g February 7, 2011 at 9:08am
    There is no intonation adjustment once the rivets are set. You can either set the intonation with a dummy bridge then mark your mounting holes or set the bridge close to correct and then file the bridge to change the string exit point. part of the beauty of these instruments is there unique sound (yes even imperfect intonation is OK) and the fact that there are really few rules that you NEED to follow so don't get caught up too much just build and have fun. Also in the future I will be making knurled height adjustment knobs on the lathe instead of the unsightly nuts, but couldn't justify them for the amount my friend was giving me to make this sucker.
  • MichaelS Country Boy Guitars February 6, 2011 at 6:49pm
    Is there any intonation adjustment with this?  Neat looking bridge anyway.


    mike g said:
    heres a few pics one of the riv nut gun and one of the mounted bridge w/o slots and set at the lowest point which once slotted shouls put the strings almost on the frets. there is about .250 adjustment available but more if you get longer screws.
    305698491?profile=RESIZE_1024x1024
    305699630?profile=RESIZE_1024x1024
  • mike g February 6, 2011 at 5:23pm
    heres a few pics one of the riv nut gun and one of the mounted bridge w/o slots and set at the lowest point which once slotted shouls put the strings almost on the frets. there is about .250 adjustment available but more if you get longer screws.
    305698491?profile=RESIZE_1024x1024
    305699630?profile=RESIZE_1024x1024

  • Wichita Sam February 6, 2011 at 2:28pm

    very nice looking.... send pic of it inplace... should be great...



    mike g said:

    thanks much. I'm just about to mount a handmade adjustable bridge and will follow your advice. the reasoning is sound and makes perfect sense. here is a pic of the bridge pre slotting.

     

    bridge info:

     

    this bridge is 1/4" copper stock milled and filed to the shape you see and uses two metric panhead machine screws with some nuts underneath to lock the screw 305695910?profile=RESIZE_1024x1024under the bridge and at the bottom and will be affixed to the soundboard via two Riv-Nuts. If you don't know what Riv Nuts are they are  rivets that have threads in them so you can pop rivet a piece of sheet metal and ad a threaded attachment point. I experimented and found that these fasten well to the soundboard albeit in an awkward way. rather than spreading out on the backside of the soundboard they actually spread somewhere between the front and back of the board like a concrete anchor. you need to be careful not to overdo it and crack the wood. after attachment you can put a few drops of gorilla glue to the back side for extra support. just figured i'd share my little project. wish me luck.

     

    oh yeah and thanks much for all the great info and personal help.

  • mike g February 6, 2011 at 1:58pm

    thanks much. I'm just about to mount a handmade adjustable bridge and will follow your advice. the reasoning is sound and makes perfect sense. here is a pic of the bridge pre slotting.

     

    bridge info:

     

    this bridge is 1/4" copper stock milled and filed to the shape you see and uses two metric panhead machine screws with some nuts underneath to lock the screw 305695910?profile=RESIZE_1024x1024under the bridge and at the bottom and will be affixed to the soundboard via two Riv-Nuts. If you don't know what Riv Nuts are they are  rivets that have threads in them so you can pop rivet a piece of sheet metal and ad a threaded attachment point. I experimented and found that these fasten well to the soundboard albeit in an awkward way. rather than spreading out on the backside of the soundboard they actually spread somewhere between the front and back of the board like a concrete anchor. you need to be careful not to overdo it and crack the wood. after attachment you can put a few drops of gorilla glue to the back side for extra support. just figured i'd share my little project. wish me luck.

     

    oh yeah and thanks much for all the great info and personal help.

  • Wichita Sam February 6, 2011 at 1:39pm

    mike g,

     

    it is the small gauge strings that deform the most, resulting in the greatest pitch shift (to the sharp side), so that it is the treble end of the bar that is made shorter vs. Scale Length to compensate for the shapening of the fretted pitch....

     

    If you think about it, there is no mechanism that would make a string pitch down (flat) when fretted, unless the fret itself was in the wrong place....

     

    the best,

     

    Wichita Sam

  • mike g February 6, 2011 at 11:09am
    I thought that you make the heavier strings a little longer with regards to the scale length rather than shortening the smaller strings. I have conflicting input....what to do?
  • D.C. Mansfield February 4, 2011 at 1:08pm

     Thanks all!

      That's cleared things up a bit.  I'm gunna try out a new floating bridge, see how I get on.

      Cheers,

      Duncan.

  • MichaelS Country Boy Guitars February 4, 2011 at 11:52am
    Very slick idea Jason, always something new in here.
  • Wichita Sam February 4, 2011 at 10:45am

    jarmo,

     

    Do you size each bead's hole to the string gauge?  If not, do you have any problems with buzzing in the smaller wound strings?

     

    thanks,

    the best,

     

    Wichita Sam

    Jarmo Katajisto said:

    This is my somekind solution to that intonation problem.
This reply was deleted.