Thread: Luthier's Tip O' Th' Day

slowhand6 - 12/7/2006 at 07:37 PM

I have been getting some really great newsletters with some very useful information. I know some of y'all will want to read up some of this stuff so I will repost them here.


Acoustic guitar pickup doesn't sound right? Don't blame the pickup, blame the installation!

by Dan Erlewine

I had a visitor Friday night: Jorma Kaukonen (of Jefferson Airplane and Hot Tuna fame) brought over his Gibson J-35:
"Dan, my saddle pickup isn't sounding right. Some strings sound weak, and others are too strong. And this guitar sure could use a refret, too."

Jorma hoped to pick the guitar up Monday morning to take it to Nashville for recording. That's a lot of work for one weekend! But Jorma's a pal, and I'm happy to help. I managed to get it all done, and also came up with this important tip for everybody who uses undersaddle acoustic pickups...

Dan Erlewine, December 7, 2006

Solving an acoustic pickup's sound problems
An undersaddle pickup needs firm contact with the entire saddle from end-to-end. The bottom of the saddle has to be flat, and so does the slot...

Otherwise, you'll have gaps that deaden the response. Also, the saddle has to sit upright in the slot with some freedom to move, like a piston in a cylinder. If it's tipped at an angle, it'll bind up in the slot, and that's another way to ruin the sound.

aren't flat.
The best Gibson flattops have lightly-braced, thin tops. Under string tension they curve into a dome, sometimes forcing their bridges to tilt forward. When the saddle is too tall (3/16" or more), it can't help but lean forward. To make matters worse, if thesaddle is loose it tips forward, making poor contact with the transducer under it. The result is unbalanced, unpleasant sound.

My neck set gauge fastens to a 24" precision straightedge, and is held upright by a slotted block of wood (above).

Another block keeps the bridge pins in order:

Jorma's J-35 had a problem I've seen before: when the pickup was installed, the strings were removed (of course), and when the guitar was strung back up, the top became arched from string tension. That saddle slot might have been flat when it was routed, but under tension it wasn't flat anymore. Also, the saddle was loose, and it leaned forward from the pull of the strings. This was double-trouble: bad contact with the pickup, and a saddle that's jammed at an angle and can't move.

Neat trick: Jack up the top to simulate string tension
I used a brace repair jack inside the guitar to lift the bridge and simulate string tension while routing the new saddle slot. This way, the slot is flat when it's supposed to be: when the guitar's tuned back up to pitch.

Measuring bridge height
Before taking the strings off, I took some measurements: with a neck set gauge mounted on a straightedge, I checked the height of the bridge under string tension. (With the strings off, the top sank down by .024".) I also noted that the saddle was tipping forward by about 4 degrees. That's bad! We'll want the new saddle to sit up straight.

I wanted to start fresh by cutting a new slot, so I routed the old slot clean and filled it with Brazilian rosewood to match the bridge. I glued my rosewood patch with slow setting epoxy (8 hour cure time) and went to bed.

Shaping the
replacement patch
Up-and-at-'em on Saturday morning, I leveled the rosewood patch with coarse and fine Dragon rasps. (Notice my sheet brass "bib" surrounding the bridge: always protect the guitar top!) I followed the rasps with a scraper blade, leaving a smooth surface that'll make this patch almost invisible.

Install the new saddle
Now it's time to establish the saddle position: The Intonator handles that.

To avoid the previous installer's mistake, let's not rout the slot with the top "at rest" again. Here's where the brace jack comes in: I'd recorded the height of the bridgeunder string tension, so now I returned the bridge to that state by lifting it from inside with the jack. With the top arched as if it were strung up, I routed the slot. This new slot will have a flat bottom when the guitar's tuned to pitch.

Now let's deal with that forward-leaning saddle
We know the strings are going to pull the saddle 4° forward on this guitar, so we'll compensate by cutting a slot that leans back 4° toward the bridge pins. When it's strung up, the saddle will sit upright and move in the slot, transferring string vibrations to the pickup underneath.

Routing the slot —
with an added angle
To create a back-tilted slot, I put a shim under the front edge of my saddle routing jig. This tipped the Dremel tool 4° while I cut the new slot. In this photo, you can see the tilt of the new saddle blank in the slot. When strung back up, the bridge tipped forward as planned, and this new saddle sat perpendicular to the strings and was able to move like a piston above Jorma’s Fishman Acoustic Matrix transducer.


I pre-bend strings before installing, so the ball ends sit right up against the bridge pad. My string-bending stick is a wood dowel with an L-hook made from a #4 finish nail.

Bone for tone
The hard work was done, and I moved on to the new nut, new saddle, and new bridge pins. Jorma's choice for tone on all of these is bone. The J-35’s warped plastic bridge pins went straight into the wastebasket.

The new bone pins sat a little tall, so I slightly reamed each hole with a 5° pin hole reamer, giving each hole just a twist, not even a full turn. I gave each pin a custom slot to match string sizes, using a bridge pin slotter. With the head of each pin well seated, each string is held snug, with its ball end firmly against the bridge plate below. I notched these custom-slotted pins with tiny nicks from a nut file (I, II, III, IIII, IIIII, no mark on the 6th). This way, Jorma will know which pin goes where when he changes strings (he uses Gibson Bronze-wound lights, gauged from .012" to .052").

Along with a careful refret, the nut and saddle were replaced with vintage bone. All the work went faster than I expected, and the guitar was finished by mid-afternoon Sunday. That gave it some time to settle in and get comfortable with all these changes it just went through! Monday morning it was ready to come out singin' when Jorma took it to Nashville!

slowhand6 - 12/8/2006 at 12:47 PM

Here’s a quick fix for a chipped finish:
use a drop of super glue!

When your peghead smacks the drummer’s ride cymbal and a piece of finish pops off, here’s what to do. All you need is some Super Glue, a toothpick, and several grits of sandpaper. (I used a little red mahonany stain, too.)

Dan Erlewine

Fix a finish in a jiffy with super glue

Here’s the chip.
Modern poly-based guitar finishes are hard plastic, and when they’re damaged, pieces fall off. The simple repair we’re about to do is called a “drop-fill.”

I dabbed some Behkol solvent on it with a Q-tip. This shows how the chip will look with clear finish on it. The Behkol dries in a few seconds — enough time to show that the look is just a little too light.

I decided to brush on little ColorTone Red Mahonany Stainto replace the color that went away with the finish chip.

#20 Super Glue (medium viscosity) is my choice of finish. I squeezed some out onto the lid of a cottage cheese carton, and used the bent tip of a Drop-fill Toothpick for my brush. Be patient! Let the glue cure for at least several hours — the longer the better.

Sand the drop-fill by pulling narrow strips of Fre-cut Gold sandpaper across it under gentle pressure applied by your fingertip. "Run the grits" starting with 320-grit and working to 800-grit. This entire sanding operation takes less than 5 minutes; each grit gets no more than 30 seconds.

When I reach 800-grit, I switch to Micro-Mesh abrasives, using them wet. Micro-Mesh does the buffing. I keep strips of Micro-Mesh sandpaper in water at all times, hanging them on the rim of my cottage cheese carton of water.

Not too shabby!
After polishing with Micro-Mesh, the repair is smooth and shiny. I'm happy and so was the customer.

slowhand6 - 12/8/2006 at 12:48 PM

For those of you that don't know Dan Erlewine is the Godfather of Lutherie (much like James Brown to Soul, Robert Johnson to Blues, etc).

He is the definitive for fixing all things guitar!

Peace~! Brian

pilarchild - 12/8/2006 at 02:51 PM

He ain't cheap either

Charlesinator - 12/9/2006 at 03:22 PM

On the subject of tooth picks and glue ... Should you want to change strap buttons for some strap locks and find that the screw hole is stripped out. Just fill the hole with glue (I like Elmer's) and bits of tooth pick or matches without the combustable part of course, then allow to dry and put the screw back in. Should hold fine although now some straps are coming with built in strap locks. Way cool!

slowhand6 - 8/17/2007 at 05:24 PM

StewMac's most recent newsletter seemed appropriate for many of us to do a quick read on here. How to troubleshoot electric guitar saddles (a somewhat abbreviated version of their newsletter I received)

Keep that saddle clean, partner...

Lots of guitars show up with saddle problems:
-Sharp saddles that break strings
-Worn saddles with burrs that pinch the strings and mess with tuning
-Wrong-size slots that cause buzzes

Gibson Style Bridge
Here’s a Gibson that’s been causing trouble onstage by breaking strings. Look how badly corroded these saddles are. See that whitish buildup? They’ve developed rough edges that snag and break the strings.

Remove these crusty metal parts and give them a good soak in a mix of naphtha and 3-in-One Oil. This saturates the parts and helps loosen them up. I used a toothbrush to remove the corrosion and loose rust, then carefully removed the screws. (Wear protective gloves to handle these chemicals.)

After the toothbrushing, I gave the parts another bath in a fresh batch of the naphtha/oil mix, followed by a quick rinse in acetone to degrease them. I dried them off and used a fret dressing stick to take off any remaining crud. I also used the dressing stick to smooth out any nicks in the saddle while I was at it.

I cleaned up the slots with nut slotting files, then followed up with abrasive cord to remove any file marks and smooth out the string surface nicely.

I reinstalled the saddles, using understring radius gauges to make sure their saddle radius remains true (higher saddles in the middle, lower on the ends).

This bridge is now ready for more years of live playing.

Tele: Threaded Saddles

Many Telecasters have 3-saddle bridges rather than 6 saddles. Some of these saddles are cut from screw-threaded rods, and don’t really fit string gauges properly. These can often buzz and break strings, and on top of that, it’s hard to get precise string spacing in those threads.

For these, I determine the string spread with my string spacing rule and then use nut slotting files to open the threads to fit the individual string gauges. A 3"x5" card protects the bridge pickup from the filing. These properly-spaced slots aren’t so prone to breakage and buzzes.

Tele: Smooth Saddles
Teles with unnotched brass saddles have tuning and string spacing issues, especially for the heavy-handed player.

For these, I’ll again lay out the string spread and notch the smooth saddles.

Unwound strings: Slot the saddles just deep enough so the top of the string is flush with the top of the saddle.

Wound strings: Slot the saddles so approximately half the string is seated in the saddle. This prevents unwanted buzzing in the saddles while securing the strings. Clean these up with abrasive cord and set the radius with the understring gauges and we’re ready to rock.


These rusted, worn saddles have bad string-to-saddle contact, resulting in buzzing. Before removing them, I measured their locations so it was quick to re-install them in the same intonation. The screws were difficult to turn, so I soaked these in the napatha/oil mix.

When they came out of the oil the screws turned freely, and they cleaned up well.

I smoothed out the grooves and burrs with needle files and a fret dressing stick. When doing this, watch for sharp areas around the height adjustment screws. I went over the saddles with Micro Mesh pads to polish them up, and got nice smooth saddles with excellent string contact.

Why wait for trouble before cleaning up your saddles? (That’d be like waiting for a cavity before brushing your teeth!) Saddle cleanup is part of my regular maintenance routine on customers’ instruments. Better saddle/string contact means better transfer of tone and sustain — and happier customers!


aiq - 9/9/2007 at 12:49 PM

If you have a Gibson guitar and need to touchup a finish blemish read the following:

Charlesinator - 9/10/2007 at 12:02 AM

Thanks for that post John. I have had a ding in my LP since two days after I've bought it.

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