MENG 351 Guitar Project

MENG 351 Guitar Project

Neck Operations

Materials

Wood: ¾” x 2.25” cherry. ¼” wide spruce filler stick. Birch veneer.
Hardware: 1/4" x 3/8” steel bar for reinforcement (“truss rod”). Two ¼-20 threaded inserts
Medium-viscosity superglue (cyanoacrylate) and accelerator

Prepare Neck (Loma 7)

Miter Saw

Review instructions behind saw; see instructor if machine is new to you.
Cut neck stock to 24.0” length.

Table Saw

Review the Table Saw instructions posted on the fence.
Check the calibration of the Wixey digital fence read-out (rip a test piece and measure with calipers).
Inspect the 2 edges for straightness. Do a minimum clean-up on any rough or wavy edges. (Omit featherboard if edge is very rough.)

Rip stock to 2.25” wide, +/- 1/64”. Avoid feeding too slow—will burn the wood.
Inspect the wood for bow along its length:
Place the wide (2.25”) face against the fence. Solid wood is usually slightly bowed; Check that the bow is less than 1/32”, preferably ~1/64”:

In pencil, mark the Top and Back as shown.

On the Back Side, mark lines across the 2 1/4” width, at 3 1/4” and 6 1/8” from one end:

Cut Headstock Scarf Joint:
Setup the Table Saw Cross-Cut Guide in the slot to the right of the blade (left pic below).
Raise the blade to 2.75”.
Install the Adapter Clamp pins into the Cross-Cut Guide holes (left pic).
Rotate the Cross-Cut Guide counterclockwise to 15 degrees (pull pin), and lock.
Install the neck to the left of the Adapter Clamp with the neck’s back side towards the blade. Align the 6 1/8” line with the front face of the clamp (right pic). Check that the blade touches the 3 1/4” line. Clamp securely.

Stand to the right of the blade. Pull the Adapter Clamp tight to the Cross-Cut Guide (left pic).
Carefully cut the scarf joint in one ~slow, smooth motion. Don’t feed too quickly, as excess force will result in a curved cut. (right pic)

Truss Rod (Steel Reinforcement)

Prepare Truss Rod
Horizontal Bandsaw: Cut 1/4" x 3/8” steel bar to 16.0” long.
Disc Sander: Deburr ends so sides and corners of rod are smooth (Picture at left).
Clean/degrease thoroughly with Simple Green and Scotchbrite pad (Picture at right), followed by wiping with isopropyl alcohol.

Table Saw: Cut Slot
Set blade height to 0.50” (left pic). Set the fence to 1.00” (exact, right pic).

Place the angled end towards the blade (push stick fits square end). Cut the slot (full length).

Set the fence to~1.06” and repeat.
Set fence to 1.14”(exact) and repeat.
Check the fit of the steel bar in the slot. A slip or slightly snug fit is ideal. If too tight, set the fence 0.01”wider and rip again.

Obtain a ¼” wide Spruce filler stick. Check that it fits snugly in the slot.

Mark the back of the neck at 1.0” inboard of the old 6 1/8” line, to define placement of the rod (right pic).
Test fit the rod in the slot, with one end aligned to the new 1.0” mark.
Verify that the whole length will sit 1/8” deep in the slot. Remove the rod.

Square End (not flush to end)Scarf Joint End (at 1” line)

Apply beads of superglue (CA20) to the inside of the slot, to both side walls.
Fit the rod in the slot, aligned as above. Press or hammer in securely along its length (left pic).
Apply superglue to the inside of this “new” slot. Align the filler stick with the square end. (right pic). Press/hammer the filler stick into the slot. Let dry 1 minute.

Belt Sander: Sand the Filler Stick flush with the back of the neck. Orient neck ends vertically so sanded surfaces remain flat.

Finish Scarf Joint
Flip the endpiece over and fit to neck as shown below. Alignthe top faces with a ruler. Check for good fit all around (see instructor if not). Pencil a short line across the aligned joint for use later.

Apply supergluefairly generously to 1 face, align the pencil marks, and clamp securely for 3 minutes using 4 clamps (don’t use accelerator beforehand – repositioning may be needed). Quickly inspect the joint and move the clamps as needed to close any gaps.

Carefully sand the top and side faces flat, until the joint is smooth.

Headstock Veneer:
Obtain a piece of 3M sticky-back (PSA) maple or birch veneer (left pic).
Align edge of veneer just to the left of the headstock’s beveled edge (right pic). Press veneer to surface.

Press/rub veneer securely onto headstock using wood or plastic (left pic).
Trim extra veneer with a razor-knife (right pic).

Using a ~150 grit sanding block, sand edges of veneer flush to headstock (left pic).
Sand the beveled edge so that the veneer isn’t higher than the neck’s fretboard surface (right pic).

Cut Nut Slot
Install the Cross-Cut Guide and set at the standard 90 angle.
Raise Table Saw Blade to 0.187” (3/16”, 6/32”, picture at left).

Make a pencil mark aligned with the transition from headstock to neck.

Position the Neck so the pencil mark is aligned with the table saw blade (left pic). Cross-cut the nut slot right through this angled edge:

Headstock Layout
In pencil, layout the 6-hole tuning-machine pattern, 3/8” inboard from sides and 1.5”, 3.0”, and 4.5” from nut slot (left drawing)
On the back of the headstock, layout the end-of-headstock design, approx 6.0”from slot (right drawing). A suggested design is shown, or, design your own.

Layout end pattern on back of headstock

Pocket Neck Joint hole layout and End-of-Neck line
On the top surface, layout 2 hole pattern and the end-of-neck line, measured from the nearer edge of the nut slot. (Hole diameter will depend on type of neck joint, below.)

Drill Press

Review instructions for drill press posted on the belt cover; see instructor if needed.
Set speed to 2000-3000 rpm.
Headstock:
Hold Headstock in vise, using Guitar Headstock Backing Block to support back surface.
Install ¼” diameter brad-point drill bit (left pic).
Carefully line up tip of drill bit with center mark.
Drill 6 holes perpendicular to the headstock surface. (No pilot hole is needed for wood.)

Pocket Neck Joint: There are two options for the holes (locations marked on the prior page): Visible screws (1 minute) and Blind screws (15 minutes)
Visible screw heads (limited to a maximum of 15 frets): Drill the 2 holes at 3/16” dia.
Blind screws installed from inside:
Drill 2 center-holes 1/16” dia, perpendicular to the neck surface.
Turn the neck over for drilling on the backside.
Install a 11/32”brad point drill bit.
Set the Drill Press Depth Stop so the drill will not break through the top surface – suggested hole depth is 9/16” (left pic).

Carefully align to the 1/16” holes and drill these blind holes (left pic).
Install Threaded Inserts into holes using a 6mm Allen key. Install and gently sink to bottom (right pic).

Tablesaw/Chopsaw/Bandsaw

End of Neck Cutoff at 17.06” line
First check that the steel rod is set inside far enough to clear the blade (left pic).
If cutting with the tablesaw, transfer the 17.06” pencil line to the side as shown (right pic).

Cut the end-of-neck at the 17.06” mark (left pic).
Optional: Bevel the top edge about 1/8” with the sander or a file (right pic).

View from back of Tablesaw

End of Headstock

Bandsaw: Turn the neck upside down so the headstock sits flat and stable on the bandsaw table (layout lines were made on this back surface—page 7). Cut the pattern.

Sand as needed. Do final sanding with a 120 grit hand sanding block to remove any burn marks.

Fret Slots (Loma 5)

Frets are small T-shaped metal ribs installed on the neck, which allow changing the length (and thus frequency) of the vibrating string. Frets have this cross-section:

Fret locations are calculated from this formula (n is the fret number, 12 breaks the octave into 12 notes, and 2 doubles the frequency over 1 octave):

Below are the first 19 fret locations for a 25.0” Open String Length (distance from inside edge of Nut to the Saddle. Also has 0.015” nut compensation). The number of frets is up to you; logical values are 7 (for chords), 12 (1 octave), 14 (at the body joint), 15 (1 beyond body joint), or 19 (whole neck, but the extra 4 are mostly cosmetic). 14-15 are suggested.

Fret / Distance from
Number / Nut Edge
0 (Nut) / 0.000
1 / 1.388
2 / 2.713
3 / 3.963
4 / 5.142
5 / 6.256
6 / 7.307
7 / 8.300
8 / 9.236
9 / 10.120
10 / 10.954
11 / 11.742
12 / 12.485
13 / 13.187
14 / 13.849
15 / 14.474
16 / 15.064
17 / 15.621
18 / 16.146
19 / 16.642

Tape the Fret Guide to the Neck, aligning the nut slot with the aluminum bar.

Use the mini-table saw to cut 7, 12, 14, 15, or 19 fret slots. If you aren’t sure, use 15 frets.
Pass the neck only forward through the blade (lift it up instead of pulling it back through blade).

Taper Neck (Loma 7)

Initially, the nut width is tapered to ~1.78”; it will narrow to 1.75”with final sanding.
On the back-side, pencil two lines across the neck:
1 line at 3/8” from the nut slot.
1 line at 13.0” from the nut slot.

Tablesaw
Raise the blade to its full height (3.0”).
Install the Vertical Featherboard Attachment on the fenceadjacent to the blade, and set the magnetic clamps (left pic).
Set the featherboard lightly on the neck and tighten the featherboard clamp (right pic).

Obtain the 5/16” Taper Spacers and securely tape them to both sides of the Headstock (left pic). Check that the tape is secure by sliding against the fence (right pic).

Set the fence at 2.32” - 2.34”. Adjust the fence so the blade just starts to touch the neck near the 13” line (+/- ½”). (left pic)
Rip the taper until the blade just reaches the 3/8” line(right pic).

Disconnect the Wixey digital read-out head from the fence (magnetic attachment, left pic).
Lower the blade. Slide the fence to the left of the blade. Raise the blade to full height again.
Setup theVertical Featherboard Attachment , next to the blade (right pic).

Adjust fence to just over 2 5/16” (equivalent of 2.32” – 2.34”, left pic). As before, adjust the fence so the blade just starts to engage the wood near the 13” line.
Rip the taper to the 3/8” line as before.

Measure the nut width. It should be between 1.74” and 1.78”. Adjust the fence and rip either/both sides again if needed.

Headstock Transition
Be careful sanding the transition from neck to the headstock – it is easy to gouge. Don’t further narrow the width at the nut slot.
Pencil a diagonal line ~¾” up the headstock as shown (left pic).
Use the Spindle Sander to sand to the line, or form a radius (right pic).

Radius Neck(Loma 5 - 6)

Pencil mark a line on all sides of the neck, 3 3/8” from the blunt square end (this line corresponds to the joint at the body).

On the back of the neck, layout the first set of boundary lines for rasping.
Here is the basic cross section of the first cuts:

Draw these boundary lines for the Headstock (left) and Body Joint transitions:

Clamp the neck upside-down in a vice flush with the 3 3/8” line, using double-wrapped paper to protect the wood. The vise jaws will simulate the body side, preventing wood removal behind the 3 3/8” line (left pic).
We will use a 2 tools to carve the neck: A rasp and a coarse file, both half-round (right pic)

Use a large rasp (a very coarse file for wood) to make heavy chamfers on both sides of the neck, cutting to the layout lines.
Hold the rasp at both ends for control.
Use long sweeping strokes down the neck to avoid local gouges (left pic).
When rasping the far end of the neck, support the headstock against your torso (right pic).

Use the round side of the rasp to taper the chamfer within the lines where it meets the headstock and body.

Continue with the rasp, chamfering the edges from the last cuts to create a finer-facet face, then rounding over all edges to create a smooth surface. Again, use long sweeping strokes up and down the neck for uniformity.

Use the rounded side of the rasp to access the neck-headstock inside radius.

Aim to remove material for an elliptical cross-section.

Once the rasp has made a uniform surface, switch to a largecoarse file and remove rasp all lines.The wood grain at the headstock and body joint transitions are prone to fraying—minimize this by stroking the half-round file towards the middle of the neck—not towards the ends.

Place coarse (80-100 grit) sandpaper under the file to remove the file lines and blend transitions.

Switch to a 1”x~12”length of 100-150 gritsanding strip, sanding shoe-shine style.
Keep moving up and down the neck to avoid gouges.
Keep the included angle more than 0° (splayed) to avoid narrowing the string-side.
Inspect the surface closely: you will probably find rasp lines that have not been fully removed. Remove these with the coarse file (sandpaper would take forever).

Measure the width of the neck at the nut slot: the goal is 1.75”. Use a sanding block to narrow the sides of the neck as needed. Round over any new edges created by this step.

Finish-sand the back of the neck with 180-240 grit sandpaper, this time sanding along the grain. Use a sanding block, or layer the paper to insulate your fingers.

Check the fit of the neck in the pocket joint. If too tight:
First thoroughly file the inside of the pocket joint to remove glue and other protrusions.
Then carefully belt-sand the sides of the neck until it is a slightly snug or slip fit.

Obtain a 24” straight edge to check that the top neck surface is flat or bowed no more than 1/64” (concave up, like on page 1):

If the bow is excessive or convex, sand the surface flat using a 80-150 grit sanding block (pic below). Avoid sanding the headstock veneer.
Once the surface is flat, lightly sand the fret surface with a 180-240 grit block.

Lightly chamfer or radius allsharp edges with120-180 grit sandpaper (folded over works well) and/or a file.

Carefully inspect and continue sanding the surfaces until you are satisfied. Flaws will be more visible after a finish is applied, and it is very difficult to correct them then. A bright light greatly helps inspection.

Clean-up the rasp and files with a file-brush before putting away.

Neck Finishing (Optional—at least 1 coat is recommended, Loma 6)

Be certain you have sanded the surfaces to your satisfaction before applying finish.
A good finish is “built” a thin layer at a time.
Apply enough to fully wet the surface, but not so much that it appears to have thickness.
Inspect along the way to wipe up any runs – especially look at the edges and surfaces adjacent to the surface just covered.
Don’t apply it thick– this causes runs, sags, uneven spots, and then more work to smooth out.
A bright light is essential to observe finish quality.
Using gloves and a small (~4”x4”) clean/lint-free paper towel/rag, apply dewaxed shellac (Zinsser Bulls Eye SealCoat) to the entire neck.
Shellac dries extremely quickly, so avoid going over the same area twice. Apply to a small area (e.g. one face of the headstock), move on, and quickly wipe up runs.
Be careful on the fretboard to not get shellac in the fret slots. Use a razor to clean these out if needed (right pic).

Let the shellac dry 1 hour.
Run your hand over the surface: you’ll notice considerable roughness.
Using 220-320 grit sand paper, lightly scuff-sand all surfaces a few times. Apply no more pressure than the weight of your hand (pic below).
The goal is only to take off the high spots—any heavier sanding will cut through to wood.
Check that the surfaces are smooth.