Simple Guitar Repairs 5: Radius Gauges and Intonation

Read Time 3 Minutes

As promised in number 4, here are the instructions to make your own fret board radius gauges. We’re going to do the intonation on your guitar, too.

Radius Gauges

I got my gauges from Stew-Mac years ago and they no longer have the cheap ones I have. Their really nice aluminum ones cost $22.95 now. You’re going to make your own for free.

Start with the cardboard back from a writing tablet, light cardboard box – even business cards will work fine. You just need something stiff enough to hold up and measure fairly accurately.


I made my cards 2 X 3 but you can use anything you like as long as the card is longer than the neck is wide, and you have room to hold it.


My cardboard is fairly thick so I used the kitchen shears shown in figure 3.

A straightedge and a utility knife will do a good job as well.

I always have scraps of plywood lying around my garage/shop so I grabbed one and made this little jig in figure 4.


Figures 5 and 6 show how to draw the radius. It’s much easier to do than it is to describe! Try to place your card as close to the center as you can so the line you draw is fairly even across the card.


To fine tune your string length, turn the pencil slightly to wrap up the string and make it shorter, or go the other way to make it longer. Just pinch the string with your fingers in a writing grip.

Figure 7 shows the 12″ card done.


Use your scissors to cut them out once you’re done. You can see my rejects in figure 8. Just turn the card over and mark them again.


Once you have the cards marked, cut them out. I checked the cuts with my Stew-Mac gauges and they are as close to perfect as we need them to be.


You could take a sanding block and lightly smooth out the cuts if you want but it really isn’t that critical. Figure 10 is just fine for our needs.


Don’t panic if your cards aren’t perfect… neither are mine! We just need them to set the pickup pole pieces and, maybe, the bridge.


Slip your gauges into your pocket next time you go to the music store and measure that “dream” guitar you wish you could afford. The neck radius may explain why you like it so much.


Intonation is critical to your guitar’s ability to play, and stay, in tune. If the intonation is off, the guitar will likely be more and more out of tune as you progress up the neck, or it may not tune well. Intonation should be checked every time you change strings. If you’re a gigging player, check it every day. Luckily, it’s super easy to check and to set.

Figure 1 shows where we start. You’ll need a tuner and whatever tool you need to adjust the string saddles back and forth in the bridge body (screwdriver, Allen wrench).


I personally use the two notes, open string and fretted at the 12th and not the 12th fret harmonic and the fretted note to set the intonation. I don’t feel that the harmonic method is as accurate, and I’m not alone in that belief, but you do whichever one you can hear the best.

You’re setting the precise string length with this adjustment. Figure 2 tells you what to do for the octave method I like. If you use the harmonic method, the two notes should be the same. (The 12th fret is the designed center of the scale length.) If the fretted note is higher than the harmonic, move the saddle back (lengthen the string), and move the saddle forward if the note is lower.


That’s all there is to it. Make sure the string is in tune, and retune after you move the saddle. Tune, check, adjust, tune, check, adjust, tune… until you get it. Once you have it, it stays quite well, depending on how much you bash on your bridge when you play.


That’s it for Number 5. I’ll try to get a Tele to work on so we can go through one in the near future. In Number 6, we’ll tackle those pickup adjustments.

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Doug Knight

Our “Man on the Street” reporter, with his “What’s New in Music Stores?” series, resides in Coos Bay, OR. You can find him on Friday nights at The Small Events Center at OrCoast Music in Coos Bay.

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