Classical Guitar Action Too High - Luthier Tips du Jour Mailbag
In this episode, Robbie O’Brien demonstrates several techniques to fix a classical guitar with action that is too high.
Video Transcription
[on-screen text reads: Luthier Tips du Jour Mailbag]
Mailbag question: How can I lower the action on a classical guitar that has very little saddle at the bridge?
Robert O'Brien: Today's Tips du Jour Mailbag question comes to us from New Jersey. "Robert, I have a classical guitar that has action that is too high at the 12th fret, but very little saddle at the bridge. How can I lower the action? Thanks. Austin in New Jersey."
Austin, if this were a steel string guitar, it'd be a candidate for a neck reset. However, it's major surgery on a classical guitar to do a neck reset, but there are a few possibilities. Now, I've got a guitar in my bench, it came in from Texas last week that has exactly this problem. Now, I know what you're thinking, "What a coincidence." I know. Let's go take a look at it.
Measuring string height
So using my LMI string height gauge, I've determined that I'm about a millimeter high on the sixth string at the 12th, and about 3/4 of a millimeter high on the first string at the 12th fret, so I need to lower the saddle.
Options for lowering the action
Option 1
So it's a 2:1 ratio, if I need to lower the action by a whole millimeter at the 12th fret, back here, I need to lower it twice that, so two millimeters. And on the bass side, I have enough bone exposed that I can do that. On the first string, I need to lower it a whole millimeter and a half here at the saddle, and I don't have that much bone exposed. It's very close. So one of the options is just get it down as close as you can, and live with the high action on that first string. On the sixth string, the action will be fine. That's option number one.
Option 2
Option number two would be to get out my block plane and remove a little bit of the bridge over here on the saddle slot, so that the bone would be more exposed. On this guitar, it's going to be really close, so probably shaving off a half millimeter or so off that bridge would do the trick. And in my opinion, that's perfectly doable. If you had to remove a millimeter, two, three, four, then uh-uh, you don't want to do that, but just a half millimeter to a millimeter or so, that's perfectly doable in my book.
Option 3
Option number three would be to pull all of the frets out of the fretboard, and then plane an angle into the fretboard. If you plane more on the nut end, then you're going to increase the angle back there at the bridge end, therefore exposing more saddle when it comes time to set your action. And that's what the client on this guitar has opted to do. So this guitar will get a complete new fret job, also the planing of the fretboard to increase the angle slightly. It's close enough that just removing a little bit on the nut end will get me enough to have enough saddle exposed back on the bridge end.
In extreme cases where you don't have enough fretboard thickness to do that, you want to go ahead and replace the fretboard with a thicker fretboard, and perhaps even taller fret wire. Now, those are options that all need to be discussed with the client. This client has decided to go with option number three, which is pull the frets, plane a little bit here on the nut end, and increase the angle. So let's get going.
Fret removal
So the first thing I need to do is pull all of the frets. Now, pulling the frets out, you need to be very careful that you don't chip the fretboard and damage it. Kent Everett has a great video that covers everything I'm going to do on the fretwork, pulling the frets, prepping the fretboard, installing the frets, leveling and re-crowning. Kent Everett covers that in great detail in his fretwork course available via my website.
So what I'm going to use is just a soldering iron to heat the fret. There could be some adhesive or something in there, I need to soften that and loosen it. I'm also going to add just a little bit of moisture around the sides of the fret, and that helps protect the fretboard, and it tells me when the fret's hot, you'll see it kind of start to sizzle.
But you want to be very careful pulling these frets, also that you don't damage the finish on the side here. And this finish looks like it may be some type of synthetic resin on the side here, which is prone to chipping, so be very careful. [Robert pulls the fret out of the fretboard using pliers] There we go. One down, 19 more to go.
Increasing angle
So with all the frets pulled out of the fretboard, it's now time to increase the angle by taking more off here on the nut end than on this end [Robert points to the other end of the fretboard closest to the guitar body]. And there's a variety of tools you can use, can use a number five jack plane, you can go with a number four smoother, you can even use a scraper type plane, or even a leveling type bar, with some very coarse grit, 60, 80 grit paper, and put on there, and concentrate on this end [Robert points to the end of the fretboard closest to the peghead]. Now, remember, if you have a radius in your fretboard, maintain that radius. I'll probably use a combination of all of the tools and the sandpaper to increase the angle that I want, then I'll check it with a straight edge to make sure I've got enough angle back here to start putting things back together.
[Robert works the planer up and down the fretboard between the 12th fret and the peghead]
Now, a little bit goes a long way here, folks, so don't get carried away and take too much down here. Also, if you have fretboards with inlay, truss rods, that kind of stuff, pay attention to what you're doing, don't screw it up. Once I've planed this into the fretboard, I'm going to go ahead and level it again with my leveling bar, concentrating on this end. This particular fretboard has a radius in it, a very slight radius, but I want to maintain the original radius in the fretboard.
Deepening fret slots
When I'm done planing the angle into the fretboard that allows me to have enough saddle exposed to get the correct action of the 12th fret, I'm going to go ahead and deepen the slots again. Make sure you get them down to the original depths. And a fret slotting blade works well for that.
Installing frets
Now that I've got the correct angle on the fretboard, and I've prepped the fretboard to receive the frets, I'm going to go ahead install the frets. Once again, Kent Everett of Everett Guitars has a great instructional video on how to do fret work. I highly recommend it.
Checking the action
After a little fret work to level and re-crown, this guitar is now ready for strings. So Austin, here's the guitar after I've got the strings back on, I've done a setup. And checking the action now with the 12th fret, I'm coming in at exactly 3.5 millimeters, which is what I look for on the sixth string, and 2.5 millimeters on the first string, and that's for a classical guitar. And I was able to do all that, and I didn't even have to take any off the saddle, I almost had to put a shim under it to get the action I wanted, but it came out just right, just by planing a different angle into the fretboard. So life's good. So Austin in New Jersey, thank you for your question. And with these options available to you, I think you can figure out a way to lower that action, and happy building.
[on-screen text reads: More Luthier Tips and online courses available at www.obrienguitars.com. Private and small group guitar building and finishing instruction available.]
