Intonation / fretting

Posted by Mike Whisenhunt on January 17, 2012 at 2:14pm

Ok, so here is my problem. I got a fret ruler given to me from a friend not long ago. I have used it to build a few guitars and strum sticks. It gives me 3 different options for scale lengths. Not much difference in then, maybe a total of an inch between the longest and the shortest. Anyways, the guitars I've built using it have turned out pretty well. Then, I built a shorter scaled cbg for a co-worker's daughter. I used stewmac to calculate the fret positions @ 58cm. My issue here is that any time I've made a guitar using stewmac's fret positions I end up a half step sharp by the time I get to the 12th fret. Not horrible, but it renders the whole guitar out of tune when you really try to play it.

Any ideas what could be causing it? I mean...the fret placement isn't off by a whole note...dunno if it has to do with the fret wire, nut height, bridge type, etc.

Thanks for any help on this...

Mike

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Replies

  • Mike Whisenhunt January 28, 2012 at 9:32am

    Ok, so I did a little bridge work on this one. sanded the bottom a little at a time until I had perfect intonation at the 12th fret on all 3 strings. Was an easy fix and something to keep a loot out for in future builds. Thanks for all the feedback guys!

  • Mike Whisenhunt January 17, 2012 at 6:09pm

    Yea, my bridge is moveable. I do think I've got some height issues with it though. The action is pretty high nearer to the bridge and low at the nut (I went with jumbo fret wire). I think that it is a bridge height issue I'm having on this one. I think I might invest in a handful of shaped nut blanks instead of fretwire. Just to mix it up.

    • Sean Laffey > Mike Whisenhunt January 26, 2012 at 7:29pm

      With a moveable bridge you should be able to check for the harmonic points, move the bridge until they line up . one should be over the 12th fret, one on the 7th and one on the 5fth, there's probably youtube  of some guy doing it.  If the gauges of your strings are widely different form low to high  you'll have to angle the bridge to get the harmonics crisp.

      Se this https://www.youtube.com/watch?v=CBYMJVOpjRk

      On frets, I'm looking for an old broken umbrella.. I had a one of the spines lying around in a junk box here and I've used them as part of a bridge, I reckon they'd make decent frets too, anyone trued em? they are half round and epoxyed nicely into the bridges.

  • Tim Gale January 17, 2012 at 5:03pm

    Is your bridge moveable?  I always build mine so that I can move the bridge to adjust intonation.  If the note is sharp at the 12th fret, slide the bridge back a little to make the string length longer.  If the bridge is to high, this can cause problems too.  If the string has to be stretched too far when it is fretted, it will play sharp.  When I build a guitar, I always try a couple different heights of bridge blanks to find just how low I can go before I start having buzzing issues.  I adjust my nut height to get the action I want, then adjust the bridge till I am good at the 12th fret.  Never had a problem with my frets playing off.  Hope this helps.

    Tim

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