Kenneth Michael Guitars est.1978
|KMG "Success Kit" Back assembly
Prepare the back center joint reinforcement strips (1/16” x ¾” spruce) by lightly
sanding them on a 150 grit sanding block.
The brace location will be marked on the inside of the back plate. The mark is the
position on the one edge of each brace facing the neck block. Using a square along the
centerline extend a line off the mark to the perimeter of the back. Use a straight edge to
draw the line all the way across the back. Repeat this procedure at all four brace
Mark the centerline on a piece of joint reinforcement material, place it on the centerline
of the back plate, than mark the edge of the reinforcement on the back. Extend the
reinforcement edge line the full length of the back.
To avoid interference problems, measure and than mark the contact points of the neck
and tail block on the back. The reinforcement material will stop at this point on each
end of the back.
Layout the sections of reinforcement on the edge mark drawn previously. Since the
material is too short to cover the whole length of the back, the sections need to be
butted. To conceal the joint place the seam where a brace will cross. Cut the material to
fall short of the block intersection marks that were made above.
A 20-inch piece of wood is used for a
clamping caul to glue the
reinforcement material. It should be
straight or slightly bowed. If bowed, the
convex bowed edge should be placed
down against the reinforcement.
Clamp the work board to the edge of
Always do a dry run of your clamping
arrangement, for this procedure three
cam clamps and one conventional
clamp works well.
Neatly apply glue to the reinforcement
strips, I like to use a Popsicle stick with
taper sanded on the end, a brush also
Since glue is a great lubricant until it
starts to set, its best to stabilize the
reinforcement strips with a few pieces
of masking tape.
Position the caul and clamps, carefully
apply pressure making sure the strips
align with the edge lines that were
marked previously. Clean up the glue
squeeze out using a tapered stick.
Sometimes its best to let the glue set
up a little to prevent smearing.
Once the glue dries a gentle chamfer should be sanded on the edges of the
reinforcement material. Protect the surface of the back to prevent scratching. I use a
piece of sheet metal; card stock will work just as good. Use progressive sand paper
grits 100 to 320.
It’s not absolutely necessary, but to make the process of notching out the reinforcement
a simple tool can be made from a piece of scrap wood. The wood must be cut square
and parallel. Mark the width of the reinforcement perpendicular to the length. Than
chisel out that section so the tool will straddle the reinforcement. The tool can be used
as a square and a saw guide.
The centerlines need to be marked on
the precision contoured back braces.
The two shorter braces are joined and
need to be cut to separate.
Place each brace on the back aligning the centerlines; mark the overall length of each
brace than trim to size.
Using a very sharp pencil lightly mark the intersection of each brace on the
reinforcement. Use the lines drawn previously as the guide marks both edges of
the brace. The saw guide tool we made above can be used to help stabilize the
brace while drawing the lines
Using the saw guide and razor saw cut along the marks, LEAVE THE LINE we want the
braces to fit snug in the notches we are now cutting.
Using a small chisel chip out the notches, gently scrap off any glue residue.
Its now necessary to refine the ends of each brace. To aide in the clamping
process we will not round off any of the edges at this time. The photo below
illustrates the goal.
Using a square mark a 2” line 3/16” along the contoured edge of the braces. Mark all
four braces at each end. Also draw a perpendicular line at the 2" mark to the top of the
Using lid off a container, or a coaster etc. that is approximately three inches in diameter
make an arch from the line just drawn to the intersection of the line 3/16’ from the
contoured edge. Repeat for all the braces ends. Note that AFTER the braces are
glued to the back plate the ends will be thinned to 1/16".
Use a saber saw, jigsaw, coping saw or
band saw etc. to cut the brace profiles.
Sand smooth, a piece of plastic pipe
wrapped with 100-grit paper makes
short work of the task.
Prepare a set of contouring cauls as explained HERE in the TUTOR. Tape the
cauls on the work board in the location of the brace to be glued.
Make a dry run of your clamping set-
up – three cam clamps and two
conventional clamps works well. Once
satisfied with the setup apply a neat
thin layer of glue to the brace, line up
the centerlines and apply the clamps.
Take care to make sure the brace
dose not slip out of position. A piece of
masking tape can be used to help
stabilize the brace.
|Clean up the glue squeeze out before it completely dries.
Repeat the above for each brace. If you have additional clamps multiple braces can
be glue simultaneously. Be sure to use contour cauls under each brace.
|Note in the photo below that the ends of each back brace must be
thinned to 1/16” to assure the binding will cover the rim notches.
Each brace now must be gently rounded over. We use a small block plane, note the
pieces of cardboard taped to the back to prevent damage.
|Finish each brace with progressive sanding 80 to 220 grit.
A chisel and sanding drum works well for this process an alternative method would be
the use of a flapper wheel sander chucked in an electric drill motor.