Monthly Archives: July 2011

Bone Nut and Pyramid Bridge Installation

There have been so many little jobs to complete once I got to the neck. A lot of them not necessarily related to woodworking and hence there has been a lot of schooling going on.

In the last four days I got two major tasks complete; making and installing the nut and installing the bridge. This means I am getting pretty darn close to completing.

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This is a bone nut blank. Here I cut it to length with a hack saw.

Next I want to get that 16″ radius arc pencil mark on it.

To hog it off down to the line I took it over to my 12″ disc sander. Then I rounded over the back by hand and did some detail sanding to final shape.

Here I marked out the string spacing. The 1st and 6th are about 3mm from the edge.

Then I used a fine nut file to mark the grooves. Now they are still shallow and have room for adjusting the depth.

I drilled the peg holes according to the nut string spacing. I drilled with a 4mm bit as this is the smallest diameter on my pegs.

Next I line it up the distance with this jig I made. Flip the jig around and it measures from the 12 to the nut. From the nut to the saddle is about 2 times the distance from the nut to the 12th. I say about because different strings stretch a little differently making scale adjustment necessary.

Once I have placement figured out I drill down through the first and sixth peg holes. Well actually I drilled one first, anchored it and then drilled the second. Here you can see the bridge anchored in position.

Then I made a caul to fit over top the bridge. Two holes match the bridge so it can also be anchored down with the bridge when it is glued in position.

The other five holes drilled in the caul are for downward pressure in case there is any lifting. With 4mm wood anchors installed in the holes I can then screw 4mm screws into the caul applying downward pressure onto the bridge. This was not so necessary for the center but is recommended on the ends of the bridge.

After a few hours I removed the clamp.

Most of the books and online resources I read use C-clamps, etc for gluing on the bridge. I got the idea for this self-contained clamping device off of youtube. I thought it was brilliant and error free. And I can tell you it worked very well.

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Martin Style Pyramid Bridge

Been doing a little work here and there but haven’t completed anything full stage enough to post it. Except for what I got done today.

Started on the bridge the other day and finished it today.

The bridge is a Martin style pyramid bridge, which was the predecessor to what we see on most acoustic guitars today – the belly bridge. The pyramid bridge is called so because it has pyramids on each side of the bridge. While the pyramids are mostly aesthetic they do provide mass for the bridge when gluing it down to the body. This style of bridge was common on vintage style guitars that had smaller bodies and lighter strings.

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Blank of ebony 6″ by 1″ by 7/16″. Here I am laying out the reference lines.

I actually put the cove cut on it before I took it to the table saw but here you can see me using my tenon jig for getting the angle cuts. I line it up by eye and dial it in with the screw adjustment on the jig.

A little sleight of hand to get that one cut I couldn’t do with my right tilt saw. I clamped it up and slowly did the cut from the back side of the saw. Also to do the inside angle once I had all the sides and front done I flipped the jig over to the right side of the blade and dialed in the screw adjustment slowly until the lines met up cleanly.

this is my setup on the router table for doing the cove cut. As I said the cove cut was done first before the angles. After the angles were cut I had to clean up the coves cuts a little.

Nice crisp lines.

The body is radiused so I had to sand the contour into the bridge. To do that I taped some paper down on top of the body and then some gum tape sandpaper on to the paper. I didn’t want to tape directly onto spruce.

Here you can see my detail sanders. Small blocks help to keep things manageable. And of course the 10mm dowel is excellent for the cove.

A close up of the pyramid and cove. You can also see I did a roundover on the leading edge of the bridge.

The finished bridge without bridge pin holes or cut saddle groove. It sits nicely on top of the contoured body.

I am not sure how close I am to replicating the original pyramid bridge as I have never seen one up close and don’t know the exact dimensions but I am pretty happy with how this one turned out.

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The Fretboard

Started work on the fretboard a couple of days ago and got right up to the point where I want to be. I have five days work lined up starting tomorrow so it was a good place to finish up.

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Here I have a 7mm thick board of ebony, flat on both sides and square down the sides. I am lining it up end to end with the nut in place.

Once I have it lined up I clamped a straight edge on the side of it for placement.

Then I put three pin nails in the neck and clipped them. Two at the body and one at the top and pressed the board over top to create my placement register. Now I can do away with that straight edge.

Martin guitars typically have a 16″ radius on the fret board. So to do that I had to make a positive to make a negative so I can make a positive again. So I began with a template and traced a 16″ radius on the ends of a long block and began to plane it down.

The positive. A 16″ radiused block of wood.

Then I staple some 60 grit demons on it and sand away to make a negative.

Then I put some 120 grit on the negative and sanded the fretboard.

A 16″ radius fretboard.

After that was done I cut out and sanded the circular in the end. This board is now ready to have the fret slots cut.

Laying out the lines for the cuts.

My miter sled. I have the fretboard attached to it with double side tape. Once I had it all in place I realized the sled has an index key for the notches located in the above fret rule so I didn’t need those pencil lines. (I was even off by a hair on a couple of them.)

Moving along, moving along. I just lift the rule and index the next slot.

20 fret slots cut about 0.5mm deep. The miter cuts straight across so I will have to deepen the cuts near the edges by free hand.

Not a clear picture but here I am checking the rise of the neck over the body. If you recall the neck is attached at 91 degrees so there is a gap where the board comes over top the body. For this I made a shim.

Broke out this dusty ol battle axe for this job. Attached the shim with double sided tape to a piece of ply dimensioned the same size and went at it.

The shim had to be as thin as baby’s hair at one end.

Glued in place you can see it is quite a nice fit. The opposite side has an ever so slight gap near the neck.

Now I am ready to cut the taper. For this I got out my taper cutting jig. Fortunately I didn’t have to make it specially for this cut. I made this one from a Fine Woodworking plan. Set up properly it can safely do four sides on a table leg.

Checking the cut. It fits nicely.

Glueing it in place with Titebond3. No slippage with those three pin nails.

A few hours later took off the clamps. It came out quite nice. Next day I will do a little cleanup.

Next up is the fretting.

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Truss Rod, Heel Cap and Neck Glue-Up

Got a bunch of things done yesterday. Today I was out for a bike ride and then lounging around in the afternoon. I think I lost about 2.2 lbs in fluids. In other words it is hot.  So the bunch of things I did get done all centered around the neck.

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To start I glued in the truss rod. This is a single action rod that needs to be epoxied into the slot. You can see here I used some masking tape to keep the glue-up need and tidy.

The rod clamped into place.

Then I cut two pieces of wood for the heel cap; ebony and curly maple.

After gluing them together I put the wood through the drum sander to get the ebony as thin as the space you see on the neck where it doesn’t quite reach the binding.

After thinning it down I sanded it to rough shape and glued it on.

After gluing I sanded it to final shape with a sanding block.

After all the above was done I was ready to glue on the neck. On confirming the neck alignment I decided I needed a shaving to bring it over just a hair.

The neck glued into place. Up to now I have been using Titebond 2 for all the glue-ups but for the neck joint I decided to use hide glue just in case a neck reset has to be done in the future sometime. I tried using hide glue last winter and the stuff practically cured on the stick. Just too cold. Right now the weather is hot and I comfortably had about one to two minutes open time.

It is really taking shape now. Next I will be doing the fret board.

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