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Scale length on a compensated bridge

Posted by Regicollis on March 22, 2014 at 8:37pm in Building Secrets, Tips, Advice, Discussion

For my first build I have bought a pre-made compensated bridge like this one

I want to place the bridge at the middle of the box but in order to know how long my neck is going to be I need to know from where to measure the scale length.

If we say the scale length ends at the nut then where does it start? At the middle of the bridge? At the First string? At the last string? Somewhere else?

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Replies

  • Wichita Sam March 24, 2014 at 9:47am

    For good intonation the saddle (the piece the the string fests on) is SLIGHTLY further from the nut than 2x the measure from the nut to the 12th fret.  Stew-Mac says that the low E string on a 24 inch scale should be 24.202 (+/-..030) and the high E string should be 24..084 (+/-.030).  Note that +/- number. There are many variables including string gauge and type and string height.  Even on set position bridges like you have, some builders will wait to glue them down until intonation is adjusted using an electronic tuner.

    Now the good news...for most setups and most listeners, those numbers are small enough that if you set the high E at nut to 12th fret times 2 , a compensated bridge will intonate just fine.

  • Regicollis March 23, 2014 at 4:37pm

    Thank you for the very informative replies. I feel smarter now than before :)

  • The Capo Kid March 23, 2014 at 12:05pm

     Not a very good bridge to use for your first build , I'd have gone for a floating bridge , what I'd do is decide on your bridge position and the scale you want to use , make the neck fit it to the box  , make a tail piece just a oblong piece of wood with 3 holes for the strings screw it to the end of the box , string the guitar up lay the bridge on the lid at the position you chose , tune it to pitch and move the bridge to suit , then you can drill and fix the bridge , a bit long winded I know or save this bridge for another build and go for a floating bridge .

  • Ron "Oily" Sprague March 23, 2014 at 1:48am
    Is your nut a bolt? ;-) if so, place your bridge in the middle of your box ( you may find that the middle is not the best place for best resonance, which is one reason you want a floating, as opposed to a fixed, bridge. Many builders place the bridge about 1/3 in from the tail end of the box. In either case, determine where your bridge is gonna be. The slant built into the saddle on a right handed git will start at where the first / highest pitch string should contact the top edge of the saddle, as the Kid sez. The slant will angle back towards the tail, ending where the last / lowest pitch string contacts the top edge of the saddle. Measure your scale length, which you determine (23, 24, 24.5, 25, and 25.5 inch scale lengths are pretty common) from the first / highest pitch string point of contact with the saddle, to the top edge of your nut. Check it for accuracy by measuring from the top edge of the nut to the 12th fret location, and double that distance: nut to 12th fret plus 12th fret to bridge / saddle = scale length. Use the Stewart-MacDonald fret calculator (www.stewmac.com), or the Kid's JeFret app, to calculate fret locations for a given scale length. Always measure fret locations from the top front edge of the nut; do not try to measure from fret to fret, as cumulative measuring errors can creep in to throw you off.
  • The Phrygian Kid March 22, 2014 at 10:28pm
    At the highest pitch string, which most call the first. This should be the one closest to the nut, the lower pitched ones will be compensated by virtue if the diagonal. If the highest string is a wound one ie you're using the lowest three from a guitar set or fatter, then scootch the bridge back another 3-5 mm so even the highest string has some compensation
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