Martin OM-28 kit

I want to replace an acoustic guitar that I lost in a house fire. I like to build things so I have decided to build a guitar. I have built electric guitars but this will be my first acoustic. To educate myself in the art of acoustic string instrument construction, I built a tenor ukulele from a Stewart MacDonald kit. The ukulele build was humbling but quite instructive and it served its purpose. As I neared the end of that project I was ready to order a solid wood guitar kit from Martin Guitar. I am not a loud strummer, I am a fan of finger-picking folk rock like early Bob Dylan and Paul Simon and I want a guitar that will record well. For these reasons, I picked the Martin 000/OM-28 model.This medium-size guitar has a smaller body and slightly wider neck than the more common dreadnought and has a 24.9" or 25.4" scale depending on the year. This kit is the longer-scale model. I have two books on guitar making to help me: Guitarmaking: Tradition and Technology by Jonathan Natelson and William Cumpiano and Build Your Own Acoustic Guitar: Complete Instructions and Full-Size Plans by Jonathan Kinkead. The Kinkead book came with plans for an Orchestra Model guitar so I will be able to use part of those plans in the construction of the Martin. Blues Creek Guitars has dozens of exceptional instructional videos on YouTube featuring John Hall. I am a rank amateur luthier and if I have the patience, I will watch all of these videos as I build the guitar.

The Kit Arrives

Building the M old

Trimming the Sides

Setting Neck and Tail Blocks

Kerfing

Leveling the Sides

Go-bar Deck

Curved Sanding Blocks

Wood Fill, Sanding, Grain Fill

Spraying Sealer and Lacquer

Attaching the Neck to the Body

The Bridge

Slotting the Nut

Final Setup

The Kit Arrives

I ordered the Martin kit from Blues Creek Guitars. I can't say I wasn't excited when it came. I videoed the unboxing:

The parts all look great to me. There is some natural grain variation. The book matched back:

The fret board is Richlite. Should this bother me? Don't I want an ebony fret board? Look at this:

Smooth, hard, jet black. I'll use it. (I later found an ebony fretboard at Martin's Guitar Maker's Connection, used it instead...)

Building the Mold

Kinkead says make a mold. I contemplated mold design. Since the sides are already bent and profiled - thicker at the tail end, thinner at the neck end - I decided I didn't need a deep mold. Based on a Martin mold, I used three thicknesses of 3/4" plywood. I cut these from a 21" wide by 8' long scrap of plywood from the attic:

I made radial cuts like the one shown above to allow me to move around with the big resaw blade on the big band saw. I went back and shaved as much wood off as I could without going over the line:

I repeated these steps with the other side. I cleaned up the saw cuts with a drum sander on the drill press. Here are the two halves with the plan underneath:

February 9. I gave myself a little room to mess up by scribing the center line slightly inside the mold as seen in this photo. The arrow points to the center line:

I trimmed the mold to the center line on all four faces where the two halves meet and clamped them together. Then I drew straight lines on the outside of the mold on the neck and tail ends and trimmed the outside of the mold so the edges were flush at the meeting faces:

I screwed a wood strap on the tail end and screwed an old hinge to the neck end. Here are the rosewood sides in the mold for a test fit:

February 10. I replaced the wood strap with a clasp to make the mold easier to open.

February 11. I trimmed the outside of the mold, sanded the top, back and sides. This will look nice on the wall:

Trimming the Sides

This picture shows that the sides overlap in the center. I will have to trim them:

I put a square against the straight top edge and drew a line all the way across. I have to square against the top edge since it is straight while the back edge is slightly curved:

I clamped the side to the work table under a straight piece of oak to serve as a fence and I cut the end with a fret saw:

I did the same with the other ends and fit the sides in the mold. Now they fit without overlapping:

Setting the neck and tail blocks

The neck and tail blocks are both higher than the sides as seen in this picture:

Helpful Hints from Martin say the blocks should be flush with the top so I'll do that, but cut the blocks so they sit a little proud of the back edges, to be sanded flush with the lining later. Marking the tail block:

I dry fitted the blocks in the mold with little Harbor Freight clamps. I put blue masking tape over the seams on the outside to prevent glue from squeezing out and to hold the sides together:

You can see the center marks I made on the blocks to help me line them up on the center of the mold. I spread glue on the blocks, set the clamps again making sure the blocks and sides were tight against the table. Then I opened the mold, flipped the rim over and clamped the blocks on the other side. The tail block:

I wiped the squeezed out glue off with a damp paper towel, let it dry over night:

Kerfing

Here is the kerfed lining or kerfing. Very flexible. Smells like fresh cut cedar:

I'll start with the top edge so if I make any big mistakes, I can fix them and any repairs won't show. I mounted the rim in the mold and stood it up so I could work without glue running down the sides. I played with one piece of kerfing, flexed it and it snapped in a couple of places. No big deal as far as the function of the kerfing. Just inconvenient. So I sprayed a second piece with a fine mist of water and massaged it to soften the kerfing. I was then able to bend it and clamp it for a test fit:

Gluing the kerfing. On the first try with the first strip, practically no glue squeezed out from the inner edge so I pulled it off and put more glue on. I would rather have too much glue than not enough. Perhaps by the last strip I will have figured it out:

For each line of kerfing, I let the glue dry for about 30 minutes, removed the clothespins, then scraped the excess glue off with a little scraper before it got too hard

Leveling the Sides

I have to level the sides, the kerfing and the blocks. I will do whatever works. Whatever the method, planing, scraping, sanding, I have to secure the guitar body in place. I drilled the mold in two places, drilled identical holes in the table so I can use pins to hold the mold in place:

A close up of the tail block shows that it's a little high and it has ridges left by the band saw:

Go Bar Deck

I built a go bar deck between February 13 and March 1. It first had oak sides and 3/4" plywood top and bottom. In the picture below, I am testing a home made go bar, ripped from a scrap piece of flooring

The force, according to the bathroom scale, can be anywhere from 8 to 25 pounds. Many luthiers say 8 to 10 pounds is good, using 3/16" diameter 2' long fiberglass rods. The top is bowed from the force of the go bars. I got some 3/8 threaded rod, nuts, bolts, washers:

That should do. I ordered 3/16" diameter fiberglass rods and vinyl caps from Goodwinds to make durable go bars that should deliver uniform force.

While waiting for go bars, I continue with other tasks. The big MDF disk seen in pictures above becomes a flat sanding disk with a sheet of 60 grit sandpaper glued to it:

I'm ready to sand the back rim in the picture above. This set up makes sanding sure and easy. The heavy sanding disk rotates on the pipe assuring a flat plane. No dust flying either. To be sure I sand enough but not too much, I drew a chalk line on the rosewood edge:

After sanding, checking the chalk line. It's easy to see where I have sanded enough and not enough:

I finished the back rim, flipped the body over and repeated the exercise on the top rim. I had to be more careful on the top rim because the sides are cut so that the top slopes slightly towards the neck end. I pushed on the left side of the sanding disk so it would follow this slope. Here is the sanded top rim:

Both the top and back will be slightly arched so I am not done sanding the rims yet.

Curved sanding blocks

The spruce top and the rosewood back will each have a slight arch. The radius of the top arch should be 28' and the radius of the back arch should be 15'. The rims need to be sanded at a slight angle to match these curves. First I thought of making curved dishes with a router. After more exploring, I decided to make two sanding blocks. I made them by cutting curves into 2" wide pieces of 3/4" plywood. I determined the "sag" of the curve by using this online calculator. I drew the curves using the shape of a deflected metal ruler between nails:

I cut the curve on the band saw and used the first piece as a template to cut three more pieces with the same curve. Here are the two blocks assembled with 5 2" drywall screws. 80 grit sandpaper is being glued to the block in the back:

Go bars

Fiberglass rods and vinyl caps arrive. I lined them up and marked them at 20". This should be the correct length for clamping the top or back on.

In the garage, I cut through the rods easily with an angle cutter with a metal cutting disk. Back inside I washed them off and put vinyl caps on the ends:

Joining the Back

When the two back halves are held together in front of a light, it is clear that two edges are not perfectly straight:

Sanding on this disk yields inconsistent results. So I tried the ultra flat band saw table as a sanding base. Still not consistent.

Better, but still not good enough. I need a well-honed plane iron, perhaps a longer plane. There is a slight arch in the edge that I can't flatten with this short plane.

I took the pieces to the shop teacher who generously offered the use of his joiner. This yielded the best results though even a power joiner did not give perfectly straight edges. Here are the back pieces after the joiner:

I will go with it. The back pieces will have an internal brace along the seam to give more strength to the joint. Move on.

I made a nail and baton press recommended by Kinkead. I nailed five nails on each side of the back pieces.

I put a finger-smoothed bead of Titebond glue on each edge, then inserted the herringbone inlay. After glue up, I removed the baton and pressed the pieces down. I wiped off the squeezed out glue and clamped the pieces down with go bars on clamping boards to assure uniform pressure:

This was the first time I used the go bar deck. Very fast and easy :-D Here is a close up of the joint the next morning:

After a very long break (over 2 years!), I found the time and space to continue building the guitar.

July 6. During the building hiatus, I lost two back braces so I had to replace them some how. After too much pondering, I fashioned two back braces from African mahogany. I used my handy bench sander to give the brace a curved bottom. I used an existing back brace to trace the proper curve.

Here are the four back braces. The farthest and nearest are the homemade mahogany braces:

Slot prepared, trim pieces on the left, scrap wood the right will serve as a gluing caul:

All sources say to build at about 50% relative humidity. I live in South Jersey. 'Nuff said? I got a 50 pint dehumidifier before continuing with guitar assembly. I weighed the back, top, braces and rim every day after I turned on the dehumidifier and watched the weight decrease daily for a week. Then I continued.

The top sits on curved blocks cut with a 28' radius to match the curve of the top braces. Good squeeze out indicates good glue coverage.

July 30. I sanded, chiseled, sanded again, chiseled again, both the top and the back braces until I could dry fit them with confidence. For each, I clamped them dry on the go bar deck to make sure the surfaces met correctly. Here is the top showing all the braces:

After gluing the top, I had to add 6 pieces of kerfing, cheap insurance to keep the braces from popping up when the guitar is banged around. My mistake, cutting the X-braces and the top bar too short. This is my fix:

August 1, 2016. I used the laminate trimmer with edge guide to trim the top and back, generated lots of select tonewood dust

April 20-21. I am worried about the next step, carving ledges for purfling and binding. I want to use the laminate trimmer but it is difficult to keep it vertical on the stock square base. I found a piece of sturdy plastic in my junk pile. I cut a piece out on the band saw including a wide vertical edge that should give it some added stiffness. I traced screw holes and a router hole on the plastic and drilled out holes on the drill press. The original base plate sits on the new plate in the picture below for comparison:

April 22. After a little more practice, I routed the binding channel on the back of the real guitar:

I had a little snag when I went across the end trim. Nothing I can't fix later. The channel looks good:

Next I routed the top since the top binding is the same size as the back binding. Then I routed the little step for the purfling over the back binding channel:

April 29. I cleaned up the binding and purfling channels with chisel or file as needed. I reattached the back trim then started to dry fit the back binding:

What a mess! Glue all over my hands, squeezing out everywhere to assure good coverage. I hope the excess glue will all scrape and sand off. If the glue sticks to the wood and plastic like it stuck to my fingers, I have nothing to worry about. Half way done the back:

April 30. I still had to rout the purfling channel on the top. This channel must be a little wider to accept two purfling strips. I practiced on the junk guitar:

Then I routed the channel for the top purfling on the good guitar. The router left lots of overhanging spruce splinters ready to tear out. I tried a chisel to clean up the channel.

After some experiments, I found a suitable way to clean up the channel. I gently scraped across the top to push the splinters down:

Then I scraped the edge in the direction indicated, holding the chisel perpendicular to the top surface. This took a lot of gentle scraping:

May 6. Duco running out, I got another tube at the local Ace hardware store. Then I glued the binding and purfling with lots of excess glue like I did on the back. This time I wore 7 mil nitrile gloves. Good idea. Here is the top half way done, with enough painter's tape ready for the other half:

May 14. After giving the glue a chance to dry, I tried using a cabinet scraper to level the sides. The scraper is good for scraping the plastic binding:

Over the next few months, I sanded the body. I tried scraping but it seemed to get me nowhere. Finally, I read through the applicable pages in Kinkead's book in which he uses a random-orbit palm sander on the body using 150 grit sandpaper, even on the curved sections. So that's what I did, and it worked quickly, leaving a smooth, scratch-free surface.

I was further convinced when I later saw workers at the Martin Guitar factory doing the same thing!

Early September, I started sanding the neck dovetail to fit it into the neck block in the guitar body. This is one of most critical steps. The neck must make a slight downward angle to the plane of the guitar body to yield a guitar with low action (easy to play...). I cut 10 degrees off a right angle block on the band saw to create a block with the correct angle to get into the dovetail:

I further timmed the sanding block to a shape that was easy to handle and I sanded the dovetail to lower the neck till it was flush with the guitar body.

This was a big mistake. I should have sanded the surfaces of the dovetail that touch the rosewood side first to get the correct neck angle. I sanded those parts of the dovetail next and tried using a little belt sander. Another big mistake because I sanded the neck too much, spoiling any chance of achieving a clean and strong bond without "cosmetic surgery." As luck would have it, I was in the vicinity of the Martin Guitar factory and Guitar Builder's Connection store later in the month and I was able to pick up neck for $25. Here's a plug for that little store: the people who work there were very helpful, knowledgeble and experienced, and the shop has thousands of parts for guitar makers. Fantastic. It is located near the Martin Factory, at

It was at this store that I learned that my guitar was, in fact, the OM model, not the 000 as the Blues Creek kit was marketed.The difference is only the scale length. I got over it.

So I got a second try at mating the neck with the body. I watched several YouTube videos before trying again. And I watched them over again. I found the most helpful set of videos was a 5-part series called Setting a Dovetail Neck featuring John Hall of Blues Creek Guitars. I sanded the dovetail carefully, taking many breaks mostly because it is such a critical part of the build, a daunting task. Here is the dovetail with sanding block:

You see I have glued a piece of sand paper to one side of the angled block. This allows me to work on one surface at a time. Sand, check, sand, check, etc. Here is the top on October 28:

Is it perfect? What is perfect? I won't know until the guitar is strung and ready to play.

October 30. I drilled the peghead. Not as simple as I first thought. Here is one of the tuners:

I experimented on the "scrap" neck with the over-sanded dovetail. The first hole I drilled matched the shaft diameter at the base of the tuner. I found the location by overlaying a template and making a mark with a center punch:

This hole is the correct size for the shaft but it's too big for the threaded bushing that screws in from the top into the base. Rats. I tried drilling a pilot hole through the peghead, then drilling two different size holes, larger at the bottom for the base, smaller at the top for the bushing. The practice hole looked good so I went to work on the good neck using the drill press, clamp and backing block. Here are pictures:

October 31. I cleaned up the two holes that were slightly off center with a few strokes of a round file. In another test fit, all tuners fit firmly. Top:

While at the Guitar Maker's Connection in September, I found a nice blond-streaked ebony fingerboard and matching bridge. I dry fit the ebony fingerboard to the neck, test clamped in the go-bar deck:

I put a little on the fingerboard also to make sure I had enough, clamped it up:

Glue squeezed out as it should. I wiped off the excess so I wouldn't have to scrape it off later.

On the top left of the fingerboard in the picture below there is a ledge. I used a chisel to scrape it off:

After I scraped the ledge away, I sanded the whole mahogany neck with 120 grit sandpaper:

November 3. I glued the mother-of-pearl dots into the pre-drilled holes in the fingerboard. I put a small drop of Duco cement on each side of each hole and pushed the dots in:

I sanded the board with 220 grit paper, could still feel the dots, so I scraped them with a wood chisel and cabinet scraper, then sanded again with 220 paper, then with 500 paper. Done.

Fretting was more challenging. Glue or no glue? If glue, which one? I think new frets in a new board do not need glue, though circumstances may require exceptions. This kit came with fret wire already curled to the radius of the fretboard. For each fret, I put the wire up to its slot and cut it with nippers:

I have fretted fingerboards a few times but this board had a "feature" I have not seen before: fret pockets:

The fret slots are not cut to the edge of the board, to hide fret tangs. I didn't realize this at first and cut through the ends of the last two slots. Oops. A little dark wood filler? I decided to use this feature which means I will have to grind away the fret tangs at the end of each fret. Nothing good comes easy. First I tried using the bench grinder. The grinding wheel was too big for this job, left a curve at the edge of the tang:

When I hammered in one of the frets that I had not ground enough, I cracked the edge of the board. Here is the slot after pulling the fret:

I spread the crack with a fret while working some Titebond into the crack, then clamped it. No one will ever know:

When I reset the fret in this slot, I will use a little Titebond to heal the little chips around the slot.

I tried filing the tangs with a flat file but it was difficult to work with the small fret and big file. I gave it some thought, then went with a Dremel and grinding wheel. I also threw together a little jig to clamp the fret in a convenient position:

To set the frets in the board, I found the simplest way was to make a radiused seating block out of a piece of oak flooring. I drew the radius by tracing a line with a sharp pencil using the end of the fretboard as a guide:

Then I sanded to the line using the roller end of my bench belt sander.I drove in the frets by setting this block on the frets and whacking it with a regular carpenter's hammer:

For almost every fret I was able to place a support block under the fret so I could give the fret block a good whack with the hammer. All frets installed but all frets hang over the edge of the fretboard:

I held it against the side of the board and filed. The fret ends sticking out the farthest were the first to go. This went faster than I thought it would:

November 5. I beveled the fret ends, first gently, then after rereading Kinkead's section on fretting, I filed deeper to slightly bevel the fingerboard as well. Then I filed at the same angle along the fingerboard to try to get all the frets filed at the same angle and depth:

It is recommended to lacquer the neck and body separately before gluing them together. I have some odds and ends to do before they are ready for lacquer.

The nut slot at the end of the fretboard is too narrow for the nut. I used the nut to mark a cutting line:

I clamped a piece of oak with a sharp, straight edge to act as a fence and cut through the headstock veneer with my fret saw:

I finished cleaning up the slot with saw and chisel, then taped the nut in the slot and shaped the nut ends with the drum sander:

I rough cut and rough sanded a heel cap out of the same material I used for the end trim:

I tightened the truss rod, used a straight edge along the top of the frets to determine when the neck was straight, then drew a flat sharpening stone along the tops of the frets to make sure they were level. I only used a few strokes since the frets look very flat and level. Here is the coarse side of the stone:

I turned the stone over, made a few passes with the fine side of the stone. I polished the frets with 220 grit paper, rubbing the paper along the fretboard and then again across the fretboard along each fret.

I had to fill the tiny knot on the fingerboard between the nut and the first fret. I mixed a little black acrylic latex paint with a dab of Elmer's Carpenter's Wood Filler and spread it on the knot and also on a little gap under the fret board and in the fret slots that I cut by mistake.

As I let the wood filler dry, I sanded the neck with 150 grit paper. I sanded the back and sides with 150, then 220 paper:

I sanded the top and was going to stop at 220, but when tried 500 grit, the grain started to show up so I sanded progressively with 500, 1000 and 1200 grit paper:

November 7. I cut a paper sheet slightly smaller than the shape of the soundboard:

I taped it to the soundboard to protect it as I work on the darker rosewood and mahogany. The fine dark dust will discolor the light color spruce top. Also, the soft spruce does not need pore (grain) filling because it is nonporous.

Mahogany and rosewood are open pore hardwoods. All references say to apply a grain filler to fill the pores. This will give the guitar a smoother finish. There are a lot of fillers to chose from. All sources recommend testing grain fillers on wood samples before using them on the your project. I decided to try Elmer's Carpenter's Wood Filler (left, below) and Mahogany Timbermate wood filler. I diluted them as recommended with water to get a heavy cream consistancy and I tinted them with black acrylic latex paint. I rubbed each on my scrap mahogany neck:

After I got the results above, I decided to also try the Mahogany Timbermate untinted to compare. After sanding, I got this. The green arrow is the Elmer's, the yellow arrow is the Timbermate tinted black, and the blue arrow is the untinted Mahogany Timbermate. The Elmer's is too black, the tinted Timbermate is a little dark, the untinted Timbermate is a little light. I will try testing again with different amounts of black tint:

I tried the three wood filler samples on the rosewood veneer on the scrap headstock. The blue arrow is again the Mahogany Timbermate which looks too light on the rosewood. The green arrow is the tinted Elmer's. Too gray. The yellow arrow is the tinted Timbermate. Looks the best, could be a little darker. I'll try more black tint and test again.

I progressively sanded the neck with finer and finer grit paper to bring out the grain. Here is some detail at the heel:

I made up two mixtures of Mahogany Timbermate with different amounts of black paint, one for the mahogany parts and one for the rosewood parts. Here is the lighter shade going on a test piece of mahogany:

I sanded the filler off each piece, scraped the bindings clean. Filling pores is a dirty job.

November 9. Before spraying, I taped the neck and body where I didn't want any finish. Here I measure the bridge position so I can tape it up. The bridge must be securely glued to bare wood. I followed the instuctions in the included instruction guide: measure from nut to the 12th fret, double that distance, add 1/8 inch. This gives the distance from the nut to the saddle of the bridge.

I taped an area just inside the calculated area of the bridge, so that the brigde will meet the finish cleanly:

Not seen here, the soundboard is taped under the fingerboard. The dovetail joint is taped on both neck and body. Ready to spray after wiping with a microfiber cloth:

Note that I installed an eye through the end block. I marked the center and drilled a small hole with a hand drill:

I wiped all the dust off with a microfiber cloth and shot the first coat of lacquer. Body: after 30 minutes:

I'm relying on my crack paint-spraying skills I have acquired while auto painting:

In other words, I don't know what I'm doing. I watched some YouTube videos and shot from the hip.

I scuff sanded the lacquer after one hour, had to sand down two runs with a block behind the sandpaper. Got to go easy on that trigger. Four more coats to go...

I shot a total of six coats, waiting 50 to 60 minutes between coats. I scuff-sanded with 320 grit after the first two coats, then didn't sand except to do a little touch up on the neck after one of the coats. I scuff-sanded before the last coat. The neck came out the best:

The body needs to be leveled and polished or it needs more lacquer but at least there are no runs:

November 14. Sources said wait between 2 and 7 days before wet sanding. I waited 5 days. For every finishing step, I started on the back. Big, flat surface, and it's the back! I wet sanded with P500 grit paper soaked for at least 30 minutes in water with a squirt of dish detergent in it. I went over the whole guitar, trying to sand down to a flat surface.

I didn't know how far to go.I didn't want to go through the lacquer so I stopped when the surface felt smooth. "Smooth" on the left, pebbly orange peel on the right before sanding:

I clamped the buffer in the guitar vise, seemed to be the best way to buff the surface:

I was quite unsatisfied with the result, a blotchy satin finish, with swirl marks. Not what I was looking for at all. Here it is before buffing:

November 17. I pondered, watched videos about guitar polishing, decided to try my auto polishing pads with Medium Cleaner. Here is the yellow polishing pad matched with Medium-Cut Cleaner:

This stuff is designed to eliminate moderate surface defects and "quickly reduce to a polishing rouge." It worked. On the left is the satin finish after wax buffing. On the right is the glossy result of the Medium-Cut compound:

Yes, there is still orange peel. Was I happy anyway? Yes. This was with "Medium-Cut" and there were still swirl marks and haze.

Could I spend more time on the finish? Yes. Would I rather complete this guitar? Yes.

November 24. I ground the edge of a flat file smooth with the bench grinder sanded the edge using P500, P1000 and P1200 sandpaper to make the edge "safe." I filed the ends of the frets to remove sharp edges at the base of the fret ends and along the bevels. Then I sanded the frets and fingerboard with with the same three grits of sandpaper. I finished with 0000 steel wool as recommended by all my text sources:

Now the big step: glue the neck to the body. I scraped away lacquer on any surface that might help hold the neck to the body:

I found the neck to be too loose for my liking, so I finally decided I had to shim the dovetail. I cut a very thin mahogany shim on the band saw, then sanded it even thinner to try to get the neck to fit tightly and correctly.

I chalked the dovetail as I continued to sand to get the neck to drop into the body joint.

Worried that I might sand too much and loosen up the joint again, I finally said enough, and glued the neck to the body. Here is a dry fit to make sure the clamp will do the job:

I wiped up the squeezed out glue with damp paper towels and let it dry for 48 hours. Then I removed the clamps:

Locating and Attaching the Bridge

You see above that I lifted the tape covering the bridge area. I had carefully started unpeeling it with a wood chisel, then I gently pulled it off:

The bridge must be glued in the correct location for the guitar to play in tune. Measure twice (or a dozen times), glue once... I measured to determine the distance from the nut to the 12th fret and made a fine mark with a sharp pencil on one of my many rulers. Then I moved the ruler and marked the same distance from the 12th fret to the bridge area. This distance from the nut to the bridge is the theoretical scale length of the guitar. For this long-scale Martin, the distance is 25.34". To this length a specific small distance must be added at the high E string and low E string to compensate for pressures exerted when pressing a string to a fret. After much searching and verifying, to 25.34" I will add 1/16" at the high E string and 5/32" at the low E string. This is the total distance from the nut to front of the saddle.

I measure from the ends of the 14th fret to the front corners of the bridge to make sure the bridge is perpendicular to the fingerboard and to make sure the bridge is centered. The distance measured by the ruler in the picture below should equal the distance shown by the blue line. I use tape to mark the bridge position. I have had to move the pieces of tape several times as I repeat the fine measurements.

Here are the cauls I made for this operation. The trapezoid on the left, 3/4" thick, fits inside against the bridge plate. The caul on the right will push on the bridge on both ends and in the middle. I made this caul because I only have one clamp with a deep enough throat for this job:

Having convinced myself that I have correctly located the bridge, I drill pilot holes into the soundboard at the high E hole and the low E hole using a 3/16" drill. I did not drill through the bridge plate. I didn't want glue to drip down into the body of the guitar.

To align the bridge correctly, I use the pilot holes with drill bits as pins and the blue tape:

Clamp. I have pulled up the tape here to make sure the bridge is in the right place:

December 2. I am always a little nervous drilling into the guitar... Here I drill through the bridge pin holes with a 3/16" drill bit, through the soundboard and bridge plate:

The holes must be enlarged with a 3 to5 degree taper to match the taper of the bridge pins. Here is the tapered reamer I will use:

According to a Martin Guitar youtube video, the pin knuckle should sit 1/64" to 1/32" above the bridge. The right pin sits in a reamed hole. The left pin hole is not reamed yet:

Slotting the Nut

I will use proportional spacing for the slots which takes string thickness into account. The distances between the strings will be equal with this spacing. I downloaded and printed a layout tool here:

I set the nut on the layout tool diagram and marked string locations with a sharp pencil.

There are many discussions about slotting the nut with or without expensive nut files. I decided to work with the tools I have.

I clamped the nut in a small vise and started nut slots with a sharp-edged half-oval needle file. The pencil marks do not show up in this picture:

I must mount the nut in position before I can deepen the slots because I will need to check progress as I cut. I glue it in with Titebond and clamp it:

Before I could cut slots in the nut, I needed to string the guitar to correct pitch. Time to install the tuning machines:

The mounting holes had picked up some lacquer from the finishing steps so I had to clean them up with my handy new reamer:

Before strings, I had to insert the saddle in the bridge. I carefully sanded the sides of the saddle on a sanding block...

...until it could drop into the bridge slot without binding but yet be tight enough not to wobble:

I checked the height of a straight edge the 12th fret as the straight edge sat on the first fret and the bridge. It was just a hair under 1.5mm at the high E side and about 2mm at the low E side, as it should be.

I strung up the guitar and brought all the strings to proper pitch. Of course I recorded the first sounds of the first string I installed:

It was difficult to play the guitar without a capo since the nut was not properly slotted, so I put the capo on and played the guitar a little, unreasonably annoyed that it wasn't ready to play. It has a nice bright, clear tone.

I loosened the strings and got back to work on the nut. I taped a piece of cardboard to the headstock to protect it from nut slotting tools. To help me cut slots to the correct depth, I used an idea from the Natelson/Cumpiano guitar book...

...cut a pencil in half length-wise (I used my bench sander to sand away half the pencil) and draw a line on the nut while sliding the pencil across the first two frets:

Worked like a charm! I used my Japanese fret file (width of kerf = 0.021") to rough cut the first slot, for the low E string:

I kept the sawtooth edge of the saw parallel with the plane of the peghead, as is recommended by most sources. I cut to the pencil line on the nut but not into the line. Next I chose a welding nozzle cleaner from a set of cleaners I got from a local welding supply store for $5 and change, the blue box in the picture below. I select a cleaner using a digital caliper. The string package gives the string width: 0.054" so I chose a cleaner with a width of 0.058", slightly larger than the string.

I mounted the cleaner securely in a "saw" made from a scrap piece of steel drilled to hold a couple of 1/4" bolts:

This worked very well for me. The nozzle cleaner is cylindrical thus creating a round-bottomed channel for the string. The holder is rigid and strong and allowed me to accurately guide the "file" along the slot. Here is the bottom view of the file holder showing the holes in the bolts. The file is secured by tightening the nuts against it.

I followed the same procedure for each string. I was able to use the fret saw to start the slots for all the wound strings. I used a 0.019" diameter nozzle file for the B and high E slots. Then I used a pointed needle file to flare the ends of the slots. Here is the nut with slots cut and stings installed:

Final Setup

Steps for final setup include checking nut slot depth, checking neck relief, and checking "action" which refers to the string height above the 12th fret (and the playablility of the guitar). Here I check the string height of the D string above the first fret while pressing down between the 2nd and 3rd frets. This distance should be about 0.004":

This string height is correct. I filed the slots that were slightly high, left the low E and A strings at 0.006" since these wider strings require more room to vibrate.

Neck relief is checked by holding the string down at the 1st fret and 14th fret (where the neck joins the body) and measuring the height of the string above the 6th fret. This should be between 0.007 and 0.015". My neck relief is about 0.013". Acceptable though I may adjust it a little.

2.5mm under the low E, 2.0 mm under the high E. This is on the high side. To lower the action, I must file down the existing saddle or try a different saddle. I have a bag of compenated bone saddles. The top saddle below is the Martin saddle. The middle item is a bone saddle, clearly shorter in height. I tried the bone saddle after sanding the sides until it slid into the bridge saddle slot. This gave me action that was too low, about 1.5mm under the low E and 1.25mm under the high E. This resulted in some buzzing strings and slightly decreased volume. I cut a sliver from an old gift card on the paper cutter, see the bottom item in the picture below. I dropped this sliver into the saddle slot, to sit under the bone saddle. This raised the action to a good place, a happy place:

I will probably sand the original saddle down to achieve the same happy result. I would rather have one solid saddle to most efficiently transfer vibration to the sound board.

I drilled a 1/4" hole in the end of the guitar where I had previously mounted an eye:

Determined not to leave the guitar 99.5% finished, I pulled the bone saddle and shim (right) and used it to draw a line on the original saddle (left):

I hand-sanded it on the sanding block until the line was almost gone. I didn't want to go to far. Before:

I put the sanded saddle in, checked the action at the 12th fret. A tad over 5/64th" at the low E and 4/64th" at the high E. I am not a heavy strummer so this should work.I tightened the truss rod an 1/8 of a turn while I had the strings loose. The neck relief is now 0.011". I'll leave it there, play the guitar and recheck after a few weeks and see if I need to adjust anything on this "new" guitar that I have been building since February, 2014! (If I take my breaks into account, I worked on and off for about a year on this guitar.) My first impressions: the guitar has a clean, bright tone, in tune all over the fretboard, staying in tune like a solid rock, the best acoustic guitar in my collection.