Truss Rod Cover Template
You just bought a vintage Harmony Sovereign. The truss rod cover plate is missing. You want to make your own same sized truss rod cover plate from scratch.
Sure would be nice if you had one to trace. But you don’t have one. So here is how to make an exact match.
Protractor with both pencil and sharp point options. The below version is very handy for guitar work. As you can see, the point on one side is replaceable
with a pencil.
Pair of heavy duty scissors or a very sharp Xacto knife. (Scissors are easier))
3/64 inch drill bit
Cord less drill
320 grit sand paper to smooth plastic edges.
Start with a sheet of thick paper. You need something you can cut out and trace around. You can also use a compass pencil to draw the truss rod cover right on back of
the pick guard scrap material. Marks from a compass point scribing on the pick guard scrap will leave marks visible from the front.
Set the compass with pencil installed to 3 5/8 inch.. This assumes you are making a template from heavy stock paper or cardboard.
The following step numbers match up with the circled numbers in the diagram below.
- Starting at a point 2 inches from the 8.5 inch, right side of the paper, centered on that side, draw an arc having radius of 3 5/8 inch.
This can go from almost top to almost bottom of paper.
- Mark a point on the arc just drawn in (1).
- Starting at the point drawn in (2), draw an arc, radius 2 9/16 above and intersecting with the arc drawn in (1)
- At the point on arc (1) where the arc drawn in (3) intersects, draw another radius 2 9/16 arc which should intersect with the point drawn in (2).
- Starting at the point in (2) draw an arc radius 15/16 inch to the right of point (2). This locates the truss rod template base.
- Set the compass back to 3 5/8 inch. Starting at the point where arc (3) intersects arc (1), draw an arc towards the right side of point (2)
- Starting at the point located via intersection of arc (5) marked as ”x”, draw an arc radius 3 5/8 inch towards left of point ”x”.
Arc (6) and arc ((7) should intersect roughly to the left of point (2).
- Staring at the intersection of arc (6) and (7), draw an arc radius 3 5/8 inch to the right. This forms the right side of the truss rod cover template.
Locating screw holes
This assumes you are making a truss rod cover with holes to match those in your Harmony Sovereign.
- Use the compass point and compass pencil point to locate the mounting holes in the gear head face. Don’t scratch the gear head face!
- Draw a point at the apex of the truss rod cover template.
- Draw an arc from the apex hole or point across the base of the template. This is shown above. This locates distance from apex hole to base line hole.
- Use the compass point and compass pencil point to locate the distance between mounting holes near the nut mounting area. Transfer this distance to the template.
- Drill or punch out the holes. (Not shown)
- Use the template to trace the truss rod cover perimeter and mounting holes. Cut the cover and drill the holes. Use a 5/64 inch drill bit.
Where ever holes or marking points are needed, use a sharp point, such as the one with the compass.
Harmony truss rod cover screws are #2 x 1/4 inch.
New Truss Rod Cover With New Screw Holes
Sometimes Harmony workers drilled holes in the wrong place. You can use the above compass measuring and marking techniques to make a new cover with one or more
new holes in the right place.
The images below show a gear head with a miss-aligned hole.
Use the compass points to locate a new hole. Use the point to dimple the gear head face in preparation for a new hole. Be sure to lock the compass at that
spread setting so you can transfer the new hole location to the template or new truss rod cover plastic.