ASL Breakdown Page 1 Join Neck and Body Wednesday, January 16, 2013 10:08 PM 1. 2. 3. 4. Charles did the following steps to speed things up: Lightly sanded the top of the lower bout with an orbital sander. I wrote "mark side of top with pencil line just inside the top edge" - I assume that means to avoid sanding close to the edge. Sanded the front of the body to conform to the correct angle where the neck will join (see 1st picture). This angle is critical - the "Bermuda Triangle of lutherie." The correct angle is obtained when a straightedge sits on the fretboard and just hits the top of the bridge. The fretboard is 1/4" off the body and the bridge is 3/8". This is a 1/8" difference, so at the 12th fret, there should be 1/16" clearance. Said differently, the clearance from the front of the body (without the neck on) to the bridge is 1/8". The top, in front, has to be angled for more than 1/8" by a bit in order to accommodate the frets and the inevitable pulling on the lower bout by the bridge. The first picture shows the jig used to flatten the upper part of the body that will be under the fretboard and set it to the correct angle. Sealed the top with sealer (shellac, etc). This helps provide a crisp edge when routing for the bindings. It also makes it easier to remove tape without ripping fibers when the tape used to hold the bindings during gluing is removed. Covered the sound holes to keep shellac out of the guitar. Fiberboard cut from center to edge to make a cone and held up with foam rubber (or whatever) will work - be creative!
Note: all of our guitars came out with too little height at the bridge. So the 3/32 clearance may be too much by a tad. ASL Breakdown Page 2
ASL Breakdown Page 3 Jig for sanding upper part of the guitar to the angle needed for the neck. This angle accounts for the height of the fretboard (with frets installed) relative to the height of the bridge (without saddle). After sanding, the upper bout above the sound hole will have the proper angle for installing the neck along the plane defined by the sanded part of the top. Another view showing this relationship. Prepare the neck angle on the body. Using the jig, sand the area where the fret board will overhang the body. Place the back of the jig approximately where the bridge will be. Sand vigorously, using the pencil test to make sure the entire area is in the plane described by the jig. Upper bout sanding jig Test for correct angle. When correct, the straightedge will be flush with the area sanded (above) and will be 1/8" above the top in the bridge area. Check the sanded area to see that all lies in the same plane.
ASL Breakdown Page 4 Determining the angle to be sanded into the heel block. The block must join the body in a way that continues the angle set on the top with the sanding jig down the entire length of the neck. NOTE: Charles is working on a simpler way to set the heel block angle and its joint with the body as we speak. The method may not be the same tomorrow!! Using the angle gauge to register the angle between the sides and neck (as given by the angle set into the top). Heel block angle sander Jig for sanding the heel block to the proper angle. It consists of two boards joined by a piano hinge, a 1/4" wood strip to locate the neck using the truss rod channel, and a bolt and wing nuts to set and hold and angle between the two boards. Setting the angle of the jig based on the angle gauge.
ASL Breakdown Page 5 Sanding the heel block to the proper angle. Make sure you check at least once that the gauge has not shifted between the time the angle is first determined and this step. Routing out the end of the heel block. To make further sanding and joining of the block easier, remove most of the material in the middle. Leave two rails, one on either side of the block about 1/2" to 9/16" wide. These will be easy to shape and sufficient to support the neck against the body. Routing is done by hand, as none of the dimensions is critical other than the obvious: the rails should be about 5/8" wide, and their faces must not be cut at all. The tool is a Dremel with an 1/8" bit. Remember, the neck is not glued to the body - it's bolted on. A tight fit makes this or breaks it. Checking the routed heel block against the body.
ASL Breakdown Page 6 Part of jig for sanding the heel block to fit along the curve of the body where the neck joins. This means sanding the faces of the two channels just formed with the router so that they conform to the contour of the body at the neck juncture. Body/heel block joint sander Next part of sanding jig: a sound hole cover with a tenon that fits into a slot on the upright part of the jig used for the actual sanding. Note the Plexiglas extension from this board that fits into the slot in the jig that was attached to the butt of the guitar in the previous photo. Don't round off the rim of the sound hole until the neck is fitted. As you see, this jig uses the sound hole to position the jig, so it shouldn't be contoured yet. The side of the jig facing the back of the guitar includes two 1/4" registration pins to keep the neck aligned.
ASL Breakdown Page 7 Completed heel block sanding setup with neck clamped to the upright part of the jig. Guitar is held to the side of the workbench with suction. Sandpaper is placed between the body of the guitar and the heel block. Sanding action: the paper is pulled down and to the right while the jig is allowed to rest on the guitar body. The left hand holds the jig in place in the vertical plane so that it follows the line set by the earlier sanding of the guitar top. The upright portion of the jig is then lifted with the left hand, allowing the right hand to feed the sand paper back under the jig to prepare for another pass. This process is a bit slow and tedious, but it allows the precise contour of the guitar body at the neck juncture to be transferred to the underside of the heel block. Note that the sand paper must be pulled out and down as it comes across the body. If the sandpaper will to be pulled in an upward direction, it would bevel the edge of the heel block away from its joint with the body. This would be very bad.
ASL Breakdown Page 8
ASL Breakdown Page 9
ASL Breakdown Page 10 Checking the heel block/body joint for tightness on both sides. Neck Install Installing the neck: begin by cutting a small channel in the top and binding/purflings so as to reveal the truss rod slot in the internal head block. The top material in this area will later be removed entirely, so the cut is not critical. Do be sure to reveal the entire truss rod slot, as the truss rod end exposed from the neck will be used to locate the points where the neck and body a re joined. NOTE: by this point, any sanding on the top or back should be done with a soft block and #120 grit. Tools at this step: knife, Japanese saw, 1/4" chisel.
ASL Breakdown Page 11 Completed slot. Neck symmetry checker With the neck loosely joined by the truss rod end inserted into the head block slot, check for symmetry. This measuring stick locates the center of the neck (cauls tighten against the sides of the neck). The bottom of the stick contains a center mark. The center line of the guitar at the butt end should be no more than 1/8" from the mark on the measuring stick. Now, locate the positions on the inside of the heel block where it will be bolted to the body. The two small steel rods have pointy ends. (Could perhaps use appropriate brad-point drill bits if you have them.)
ASL Breakdown Page 12
ASL Breakdown Page 13 The trick to working on the inside of a guitar is to stand it on its side. With the pointy rods inserted from the inside and with the neck located as before and held firmly, tap the pointy rods to pri ck two points on the inside of the heel block.
ASL Breakdown Page 14 The two points located above will be the centers of two threaded inserts that will receive the bolts that hold the neck on. These inserts must be placed perpendicular to the plane described by the rails on either side of the heel block. The dial device is a level, allowing the placement of these rails in a precise perpendicular position relative to mother Earth. Be sure to level to the side of the heel block, not the bottom of the fretboard. Threaded inserts. These are meant to screw into any grain except end grain. Unfortunately, here we will screw them into end grain. These inserts come with a hex tool that allows them to be screwed in easily. The neck bolts that will screw into these measure 5/16". Drilling the holes for the threaded inserts. The drill has a level indicator on it so that the hole can be placed relatively precisely. Here, blue tape is used in lieu of a depth stop.
ASL Breakdown Page 15 Thick super glue holds the inserts in place. After inserting a reasonable dab of glue, swirl it around in the hole with a Q -tip to make sure the sides of the hole are coated. Insert the inserts with the special hex tool. Finish off the inserts with a few squirts of thin super glue around the edges. This helps keep end grain fibers from being fu rther torn up.
ASL Breakdown Page 16 It may be necessary to use a tap and die set to ream out the inserts and check the bolts so that they match. I suspect the ne ed for this arises if too much glue gets in and fouls the thread of the inserts. The inserts are short, so a standard tap has to be ground off at the tip. Special tool made by Charles from a cheap socket driver that can be found at Sears near the hardware checkout counter. It allows easy handling of a hex shaft inside the guitar body to screw in and unscrew the neck. When tightening the neck bolts, first press the fretboard against the top of the guitar and maintain pressure while tightening the bolts. Drilling the recess channels for the tuning pegs. The fixture should look familiar. Be sure to support the peghead as much as possible and don't let the neck ride up on the support fixture. Insert the fretboard extension shim and mask the bottom of the fretboard around it. Be sure the truss rod will still turn.
ASL Breakdown Page 17 Spread thick super glue over the exposed fretboard underside. Fretboard extension routing Fixture for routing out the top with a plunge router. Attach the body to the suction jig. Make sure the fixture is aligned on the center of the body.
ASL Breakdown Page 18 Clamp the routing fixture to the body. Keep the clamp out of the way of the area to be routed. Clamp at the edges where there's lining to support the top. Plunge router. Note stops on lower left, set to take out material in 3 steps. The ultimate routing depth is not critical. It just has to be deep enough to ensure that the neck extension block is not proud of the top of the guitar. Hole guide for fretboard extension Guide for drilling holes for the neck extension block. When installing the neck, it may be necessary to use a circular file to make the hole a bit larger in one direction or another so that the bolts have some wiggle room to line up with the fretboard extension shim.
ASL Breakdown Page 19 Creating a heel cap. Determine center line. Project the back plane out to the front of the heel using a flexible ruler. Mark the point at the tip of the heel and draw a line to it from the bottom of the binding, just where it meets the purfling. Cut just proud of this line with the Japanese saw.
ASL Breakdown Page 20 As with the heel block joint with the body, draw a rail around the heel cap and chisel out the interior. As before, sand the heel cap rails level, checking frequently against the body until the heel cap is in position, meeting the body at the edge of the back purflings and projecting the back plane forward through the tip of the heel cap. Construct a heel cap cover out of ebony. Sand the back edge so it butts tightly up against the body. (Not shown )
Me and my guitar, now with neck bolted on. ASL Breakdown Page 21