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Jon Turner
Software & Lutherie: guitarmaking, software development & hotrods
Software & Lutherie: guitarmaking, software development & hotrods

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Spent a great 3-day weekend prepping and painting my pal Matt's 1957 VW Beetle. It's been a 9-year project but the end is in sight!

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50's Gibson R&R

So a buddy who runs a local pawn shop showed me this poor old abused Gibson nylon-string acoustic from the 1950s in desperate need of some TLC.

To be honest, it's a minor miracle it survived all these years. There were bumps and bangs (the purfling took the impact and cracked, preventing a top split -- that's what it's there fore after all), the frets were tarnished, the nut was a mess, strings were tied on incorrectly, etc. but the most significant problem was the bridge -- almost half an inch tall!  Sure, it was loud, but at what cost? That put significant leverage on the top. Imagine a lever and a fulcrum. The force exerted on the bridge was magnified 2x or more past nominal. It's surprising the top had not bellied or collapsed with that much strain.

So I took it in and gave it an R&R treatment -- polished the frets, made a new bone saddle, filed the nut, oiled the tuners, etc. and tied in some new strings.  Honestly, it's a nice little guitar now, very playable and comfortable with proper action and good feel. But best of all, it has a chance to last another 60+ years.

Before/after photos follow.
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guitarmaking: cutting the binding groove (FINALLY!) and end graft

We've had spectacular weather here over the past week (73F/23C), but Winter is approaching and these warm days will soon be gone. I've been working more to get this Claro Walnut guitar completed so that I can spray the finish.

There are a few moments during a build where you must realize that one small mistake could completely ruin a hundred hours of work. Installing the binding is one of these times.

Binding is a thin strip of wood which runs 'round the edge of the guitar. In additional to being decorative, it is functional -- it protects the delicate end-grain on the front and back of the guitar from chips and splits resulting from an impact.

Binding sits in a groove which is parallel to the sides, NOT the top/back. (Recall, the front and back of the guitar form an arch joining the sides at 3 to 7 degrees, depending on where you measure. It's only a few degrees, but that small angle would translate into a few thousandth's extra width -- a noticeable-to-the-eye amount.

I built a neat little machine which holds my router vertical, while still giving me the freedom to move it forward and back, side to size, up and down, and rotate it about the vertical axis. It was built using ball-bearing drawer slides (for the extendible 'arm'), a "lazy-susan" ball-bearing fixture under the base (allows the arm to rotate) and another lazy-susan bearing at the end of the arm (to allow me to rotate the router), and finally, some blocks of wood which form a parallelogram which is the part that maintains the vertical orientation of the router.

After several test-cuts to ensure the machine was set-up properly, I locked the guitar down and went at it. It's a tense moment using a knife spinning at 20,000 RPM to cut a groove in something you've just spent 100 hours building, so I used a flush-cut bit first. The flush-cut bit removed the soundboard overhang at the waist and at the back and did a fine job so I installed a 1/4" down-cut spiral bit and went 'round the guitar twice to cut the groove and clean up its edges. Test-fits of the Holly+Ebony binding show the cuts are perfect in depth and height.

But before I can install the binding, it must be bent to shape. That's tomorrow...
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guitarmaking: fret position markers

The fret markers for steel string guitars are visual cues for the performer to find his position on the fretboard. (In reality, they are seldom necessary for intermediate to expert players... try playing in the dark, or with your eyes closed to prove it to yourself.)

The markers can be simple or elaborate but are often just a 1mm thick disc of oyster or abalone shell, usually located at the 3, 5, 7, 9, 12, 15, and 17th fret locations.

For this guitar, I considered the idea of keeping the lines very clean, with a marker on just the 12th fret, or only the 7th and 12th, but after lots of mock-ups, somehow neither looked right to me for this guitar so I went with the traditional 8-marker layout with 5mm abalone-shell discs. Maybe I'll feel more adventurous next time?

Installation is straightforward. Mark a centerline, mark a perpendicular line on the 12th fret, drill some very slightly oversize holes [I use a 13/64th brad drill bit, as it's 5.13mm and just the perfect amount of oversize for a nice fit.)

Drilling is easy, as the neck is still flat and uncarved. Just lay it on the drill press and *carefully* drill some holes, using the "stops" on the drill to ensure the holes are not too deep. Ideally, the holes should be exactly the same height as the marker dots and a few trial holes can help find this depth.

Side markers are similar, but only 1/16th of an inch diameter. Drill the hole, dab a bit of glue on the end of the plastic rod, plug it in the hole and flush-cut off the end using my fret removal cutters. Fast, easy and fun!
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guitarmaking: carving the neck

Today's shoptime started out with good intentions: "let me just take 30 min. to sharpen up some chisels, and then I'll do those bindings. Well, while I have the sharpening kit out, I'll freshen up the spokeshaves..."

Before I knew it, 6 hours had flown past and I'm standing with a carved neck + a floor full of shavings & dust. And the spokeshaves are dull, again.

I went with an asymmetric shape (wider, and more "D" shaped on the treble side, more traditional "C" shape on the bass side) which is a pretty big diversion for me. But I've been admiring Rick Toone's innovative trapezoidal neck designs for quite some time (, and while I'm not ready to build something quite that radical on an acoustic, I got to thinking about the motion of the left hand as it rotates from treble notes to reaching for the bass strings, plus the asymmetric shape of the arch of the index finger as it related to the thumb. It seems to me that having a bit more wood would improve the posture of the thumb and could result in a more natural grip/feel. I did some quick/rough carvings on some scrap wood, cut to dimensions, just to test the feel and liked it enough to just 'go for it'. See pictures, below, for results.

It's subtle (as you can see by the contour gage photo) but noticeable, and 1st position with the thumb on the back of the neck is unique, as I blended the headstock to the neck and left more material on the treble side, right where my thumb falls. It's as though there's more wood to 'anchor' upon.

I'm eager to play it, myself, but I'm also looking forward to getting this in the hands of some local musicians, to get their take on it. Is it better? Or worse? Or just different?
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Speaking of fret jobs... here's "Old Man" a 1965 Fender DuoSonic. He's been living in the corner of my shop for a few years. It needed everything -- previous owner had a mirrored plastic pickguard, one humbucker pickup, spray-paint finish, and worst of all, he removed some of the frets with pliers and/or a pocket knife or something which caused some damage to the fretboard. Almost a basket case, but worth saving. So that's the bad news.
The good? The patina of age on the neck is WONDERFUL! spider-cracked nitrocellulose lacquer, rubs and scuffs on the back of the neck and frets worn down to nearly flush with the fretboard (no kidding!) tell me this is a guitar that has had the hell played out of it by who-knows-how-many-owners and lived to tell the tale.

I refinished in Candy Apple Green* lacquer (white primer, silver metallic basecoat, candy Green overcoat). No clearcoat or polyurethane on this one, and no finish buffing as, IMO, a mirror finish "over-restored" gloss would look silly next to a vintage neck. Like a new chrome bumper on an old car. Added some ToneRider pickups, new pickguard (for the vintage USA Fender, not a reissue, new cloth wiring, switches, etc.) but preserved the control plate and pots. Repaired & leveled the fretboard, new frets, the works...

*I know, I know... original colors are red, white and blue. But this thing had been resprayed so many different colors in its life, it deserved something different.

TODO: replace the nut, bevel those frets + dress the ends and then he'll be ready for a new home.
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guitarmaking - frets

fret 3 |fret| noun - each of a sequence of bars or ridges on the fingerboard of some stringed musical instruments (such as the guitar), used for fixing the positions of the fingers to produce the desired notes.

Fretwire comes in a surprising variety of sizes and shapes. For this guitar, I've chosen stewmac #148 (medium width, medium height); it's a duplicate of the factory-fretwire used by Martin on their early acoustics. It comes in 2' lengths and must be cut to length

Installation goes something like this:
1. prebend 2' wire to slightly tighter curve than the radius of the fretboard (ensures a tight fit and helps prevent fret ends from lifting)
2. press/hammer frets into fret slots, using PVA* glue
3. cut the wire to length (slightly wider than the fretboard)
4. file the ends of each fret flush with the fretboard, then bevel to 30 degrees
5. round the ends of the frets with a file

It should be noted that steps 2 and 3 may be reversed. In fact, I cut to length, then install up to about the 12th fret, but for the higher frets, I tend to press in the wire and cut off the excess length. Of course the Devil is in the details, as each of these steps has its own tricks & techniques but the work goes rather quickly and transforms the fretboard from a stick of wood into an undeniable guitar part.

* PVA = polyvinyl acetate, or plain white "school" glue. The glue doesn't stick to the steel frets, but it does swell the endgrain of the ebony fret slots, leading to a tighter fit.

And while I was at it, I went ahead & fit the nut and marked it for the strings, using a progressive spacing (a few thousandths wider for the bass strings, closer on the treble, to prevent the strings from feeling "crowded" at the nut. Spacing is equal at the bridge.)

Photos follow...
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Guitarmaking - narrowing the neck and radiusing the fretboard

Yesterday, I glued the slotted fretboard to the neck. Today I cut the waste wood form the sides of the neck, used handplanes, and later, the cabinet scraper, to flatten the sides to the final, correct size. Up until today, the neck was a 3/4" thick by 3" wide slab of mahogany... now it's slim and tapers gradually from the soundhole to the nut.

Next, I used my low-angle plane to shave away approx 1/32" from each side of the fretboard ( + lots of sandpaper) to create the 14" radius. Next was a final touch-up of the fret slots to ensure they were clear and of the proper depth.

At this point, I couldn't resist bolting up the neck and installing the tuning machines just to get a glimpse of what it should look like, soon.

Tomorrow? carve the back of the neck to a nice "C/D" shape
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Guitarmaking: fretboard

Last time, I discussed the math behind the spacing of the guitar frets, and how to go about calculating those distances. Today, we put that into practice and create a fretboard and glue it to the neck assembly. Lots of pictures this time.

I would estimate "only" 20 hours of work remain before installing strings and hearing its first sounds! Major work remaining: binding the body, carving the neck and permanently installing the neck to the body, making and installing the bridge/nut/saddle, applying nitrocellulose lacquer finish.
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guitarmaking: frets & calculators.

I'll post some photos of my fretcutting jig soon (basically a modified miter saw box with a depth-of-cut adjustment) but in the meantime I was reminded of a question somebody asked me recently: "how do you know where the guitar frets should be located, and how accurate must you be?"

Easy question first -- accuracy within one one-hundredth of an inch (0.01") is the industry standard and about all one can hope for. Consider, too that the fret slots (the grooves the metal fret fits into) are 0.023" wide and most frets are 0.050 - 0.080" wide. And, since it's wood, the dimensions will change a bit as humidity levels change!

My procedure, then, is: mark --> slot --> fret --> pray for the best!

So back to the question of "where?" There are at least 3 techniques:

1) use a "fret rule". Basically an aluminum rule that is already marked with fret locations for common (e.g. Gibson, Martin, Fender) "scale lengths". Just cut a fret slot where you see a line. Easy, but without understanding. And about $30.

2) use an online calculator to do the work for you, such as:

3) Use the ancient "rule of 18s" technique where one successively subdivides the scale length by the previous fret position. [note, ancient luthiers used "18", we, however, will us 17.817 which puts the 12th (octave) fret at exactly half the scale length. Why? Without getting too technical, discussing compensation, harmonics, etc... because it sounds right.)

Divide the scale length by 17.817 to get the position of the first fret, then divide the remainder again to calculate each successive position.

Example using the Martin 25.34" scale length.
Distance from nut to 1st fret = scalelength / 17.817 = 1.422"
distance from 1st to 2nd fret is then (scalelength - last fret) / 17.817 = 1.342"

Of course, using Excel or a java applet is much more convenient (some online tools even create a full-size PDF which may be taped to the fretboard for marking/cutting which increases the accuracy of marking, cutting... those thousandths of an inch errors can add up quickly!

Using Excel, use a field formula: "=(B$1-B2) / 17.817 + B2"

HOWEVER.... I've saved the best for last.

4) Calculate the first division, draw a line intersecting the scale end, and use a compass to subdivide.
Take the scale length, divide (and subdivide) by 17.817, then use a compass to subdivide. It's remarkably simple and fun. Tip:use a mechanical pencil with fine lead to avoid changes in line length (and thus, accuracy).

Here's a cute set of drawings illustrating the process.
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