Monthly Archives: October 2016

All, Guitar Making, Uncategorized, Videos

Cutting the Scarf Joint

In this excerpt from the Online Guitar Building School, I cut and prepare the scarf joint for the headstock.

Video Transcript:

Okay, we are ready to begin work on the neck! From
this single blank of wood I will cut and make the scarf
joint for the headstock and I will also cut and
assemble the blocks for the heel.
I start with a blank of wood, in this case Mahogany,
that is 1″ by 3″.
If this will be your first time hand-carving a neck, I
highly recommend Mahogany for its strength and ease of
use in shaping and carving operations. Other neck woods
may be difficult to work, so you may want to
save that highly figured

The blank should be atleast 32″ in length, although
it can be shorter if you have another blank from which to
cut the blocks for the heel.

Let’s begin by marking the blank for several cuts that
we want to make.

First I square a line 7 1/2″ from one end of the blank.
This marks where the headstock ends and where the nut
begins. This is also where I cut the angle for the scarf
joint, which in this case will be a 15 degree angle.
I pull the squared line onto the sides of the blank.

I pull the squared line onto the sides of the blank,
and use a protractor to mark the 15 degree angle
on both sides.

Then I connect where the two angled lines meet on the
bottom face of the blank. This gives a full representation
of where the angled cut will be on all sides of the blank.

After I make the angled cut for the scarf joint, I will be
thicknessing the offcut to 1/2″, so I will go ahead and
mark that now.

After I make the angled cut for the scarf joint, I will be
thicknessing the offcut to 1/2″, so I will go ahead and
mark that now.

Notice that it is the longer part of the offcut that I will
be thicknessing to 1/2″ and keeping as the headstock.
The shorter portion is waste.

To give you a rough idea of the order of operations here,
first we cut along the angled line for the scarf joint, then
we cut the headstock to thickness
and the remaining piece gets glued
to the bottom of the neck
blank creating what is called a scarf joint for the
headstock.
This is sort of an oversimplification so let’s get into
the details of how to perfect this joint.

Here I am resting the neckblank on the bandsaw table
and checking for square. However, if your bandsaw table
is not square to the bandsaw blade, I would start there
first.
The blank is slightly out of square with the table.
Notice the gap at the bottom of the square.

A few passes on the shooting board with a jack plane
trues up the side.

That’s better. There is a tiny hairline gap at the top
of the square now, but that’s okay. As you’ll see later,
any out of squareness in the cut can be corrected when
we fine-tune the joint.

I prefer to use a 3/8″ blade for this cut. On a 1/4″ blade
the teeth are too fine and the gullets between the teeth
too small to deal with such a heavy cut. Not to mention,
the narrow blade doesn’t track well.
On the other hand, the 1/2″ blade cuts effectively,
and tracks well but it leaves a very coarse surface.
3/8″ seems to be the happy medium.

I set the blade tension for a 3/8″ blade.

I make sure the blade tracks well on the wheel.

And then I set the guide bushings.

I like to set all the bushings so that I can fit a .025″
feeler gauge between the bushing and the blade.

It is always a good idea to have a well set bandsaw.
The table setup, the blade tension, the tracking,
and the guide bushings all factor into the outcome of
the cut.

The last thing I do is set the guide to just barely clear
the workpiece.

The cut is done carefully by hand, working very slowly,
only applying enough pressure to allow the piece to
move forward as the blade clears the wood. Be patient
and do not force it.
Try to keep the blade right on the line. If it drifts, gently
correct it’s course back towards the line.
It is easy to stay on the line if you keep your
focus a short distance ahead of the blade, rather than
right where the blade is cutting.

And now the thickness cut!
I set the table saw fence for a 1/2″ cut. Of course, you
can also make this cut on the bandsaw.

Okay, now let’s fine-tune the joint. I clamp the neck
blank in a vise.

I apply double stick tape to the headstock and
stick the headstock to the neckblank so that the
two angled planes line up.

I clamp two pieces of scrapwood to the sides of the
blank to act as a fence. This makes it easy to stick the
headstock down in proper alignment with the neckblank.

My protractor verifies for me that the angled plane is at
or close to 15 degrees.

The skew of the angled plane can be checked with
a square. Notice the two lines that I am checking:
The line at the top of the angled plane
and the line in the middle where the headstock and
the neckblank meet. If these lines are not
perpendicular to the sides, then the plane is skewed.
I use a block plane, not only to clean up the bandsaw
marks, but also to manage the skew of the angled plane.

As always, it’s not a bad idea to chalk up the surface
so you can see the progress of your work.

I stop to check the two lines with a square.

And then I continue working with the block plane
until all the chalk marks disappear.

Okay, the chalk marks are gone and the lines
are perpendicular to the sides, indicating that the
angled plane is not skewed.
Next, I use sandpaper and a flat
block to remove plane marks and to smooth the surface.

It is always important to make sure that the block
you use is indeed flat.
You’d be surprised how often this is the source of
problems.

This block, by the way, is 3″ by 4 1/4″. That seems to
be a good size for this task.

When sandpaper is pressed between 2 hard surfaces,
the hardwood of the workpiece and the hardwood of
the block, the grit wears down very quickly.
Backing the block with thin cork adds a bit of cushion
to the block which drastically extends the life of the
sandpaper.

Now I attach 120 grit sandpaper
Be sure to trim those loose ends of sandpaper
with a razor blade.
Loose ends have a tendency to leave a slight round to
the edges of your workpiece.

Okay, now that we have an effective sanding block, let’s
chalk up and sand until the marks disappear.
Notice how I sand with a circular motion rather than a
back and forth motion.
With the back and forth technique, the hand has a
tendency to tip slightly every time the hand switches
its momentum from one direction to the other.

The chalk marks are gone, with the exception of this
one stubborn, low spot in the corner. I’m not going to
worry about this spot. The glue joint is actually between
the headstock piece and the bottom of the neckblank.

Finally I finish prepping the surface by sanding to 220
grit.

The last thing I do to prepare the joint is sand the
bottom of the neckblank, where the headstock
will be attached, up to 220 grit.

I use the heatgun and spatula to remove the headstock.

A final check with a straightedge for large gaps, and
we are ready to attach the headstock.

In the next lesson we will attach the headstock and heelblocks.

 

All, Design, Guitar Making, Uncategorized, Videos

The End Wedge

A decorative end wedge hides the seam between the sides at the lower bout. This video excerpt from the Online Guitar Building School goes into detail about design considerations and the process for creating a clean and attractive endwedge.

Video Transcript:

Okay, the sides are looking pretty good at this point.
The addition of a decorative endwedge will make the
seam at the lower bout disappear and it will carry the
design motif that you’ve established with the rosette
to other parts of the guitar.

I clamp a board so that it overhangs the workbench and
hang the sides on the board with the lower bout seam
facing up.

I mark the center at the top and bottom of the endblock
and carry both of those centerlines onto the side with a
square.

By squaring the centerline onto the sides from both the
the top and bottom of the endblock, you may notice that
you get two centerlines. This is a relatively common
occurance.

It simply means that at some point during
radius sanding you sanded a little heavy to one side or
the other and now the endblock is out of square, like
you see here. This is not an issue. Just know that you’re
true center is directly in the middle of those two lines.
It should also be mentioned that the seam between the
two sides is not a reliable measure of center.

Now let’s make the endwedge. I use the same material
that I used for the rosette. I find a section of the
material that I am using that has similar grain and color.
That’s where I will mark out my endwedge.

I use a straightedge to make two converging lines with
the grain or any interesting banding running relatively
straight down the center between those two lines.
The taper can be dramatic or slight. It is a matter of
taste. Just know that, in order to use this method,
you cannot have no taper at all. The wedge shape of the
aptly named endwedge has an important functionality
when it comes to fitting and gluing it in place.

I cut out the endwedge on the bandsaw, staying 1/16″
outside of the line.

The endwedge can now be planed down to the line on
the shooting board with a block plane. Keep in mind that
it is best to shoot the plane from the wide end of the
taper to the thin end, to avoid catching the grain and
tearing out.

I’ve decided which face I want to be the show face and
now I flip the endwedge over to find and mark the
centerline on the opposite face.

To make a lengthwise centerline on a tapered wedge,
first I make 2 parallel lines. I find the center of each line
and then connect the those center marks with a straight
edge.

I use double stick tape and 2 cam clamps to hold the
endwedge in place.

I carefully line up the centerline of the endwedge with
the centerline on the sides and clamp it in place.

I use the endwedge as a fence for making a saw cut
on each side. A fine toothed dovetail saw or, in this
case, a japanese dsouki saw, make the cuts. Take your
time setting the cut and be very careful not to
inadvertently skate off the line. The goal is to cut all
the way through the glue line of the sides until
I reach the endblock. If I cut a little bit in to the
endblock that’s okay.

Now I move the clamps to the other side so I can
make the second cut. This is why I used the double
stick tape. So the endwedge doesn’t lose its place while
I move the clamps.

Once the two outside cuts are made,
I heat up a spatula and remove the double stick tape

Now I make several cuts to the inside so that
the material can pop out with a chisel.

These cuts are quick, rough cuts so I use a piece of scrap
as a fence rather than risking damage to my endwedge.

I adjust the fence for another cut. Every cut should be
about 1/8″ apart.

I make sure that all the cuts extend past the glue line
and into the endblock atleast a little bit. The material
comes out cleaner if the cuts are through the glue line.

I use a cam clamp as a backstop. The backstop not only
keeps the sides from moving around, it also creates
support for the first row of woodchips that I will remove
with the chisel. Without the backstop, the first row
would likely tear out onto the top surface of the
endblock. I simply press the chisel along the grain lines,
being very careful not to mar the outside saw cuts.

At this point the recess that you’ve created should be
fairly rough. I clean it up a little bit with a chisel,
however, you can easily damage the clean edge of the
outside saw cuts, so be careful.
Since the endwedge is aesthetic and not structural
in any way, I am not concerned with getting a perfectly
flat and smooth bottom.

I slightly round the edges on the glue face of the
endwedge so it doesn’t get hung up in the corners.

Now let’s check the fit…

It’s a great fit… but the two woods are so similar
in color that I believe something needs to be done
to create some contrast.
Thin wood strips can be ordered in various colors from
luthier suppliers. I can slide a wood strip in place and
see if I like the contrast of color.

That looks pretty good… but let’s see what it looks
like with a white strip.

The white strip looks great and it will fit well with the
binding that I’ve chosen to use later.

I break apart the white strip so that it overhangs the
endwedge recess slightly.
…I do the same thing on the other side.

Now we are ready for glue.
I mark with a pencil where the endwedge overhangs,
simply so I know not to spread glue in those areas.

I make sure I spread a little glue on the edges as well,
especially if I am adding wood strips to the design.

2 spring clamps apply downward pressure.

Now I make a pencil mark on the endwedge where it
meets the edge of the side.

I tap the endwedge a few times with a hammer, lightly,
to wedge it in place.
The pencil mark should move just slightly, indicating that
the endwedge has moved just slightly and now is properly
wedged.

I let this dry for atleast 45 minutes.

Now to remove the excess…
First I trim the wood strip with a razor knife.

A flush cutting saw works best for removing the overhang
because the saw’s teeth are angled up slightly, so you
don’t mar the surface of the endblock. Other saws or
methods can be used as long as you are careful not to
mar the endblock.

It’s not a bad idea to place a clamp over the endwedge
while you cut, so you don’t accidentally force the
endwedge loose.

When you selected the wood for the endwedge, hopefully
you selected a piece that is thicker than the side
thickness and now the endwedge is sitting proud of the
surface.

I level the endwedge with a block plane until it is close
to flush.

Then I switch to sandpaper on a flat block to bring it
completely flush.

Let’s sand it to 220 grit just to see what it will look like
all smoothed out.

It is important that the endwedge is either perfectly flush
or a little shy of the glue surfaces for the plates.
I carefully use a chisel to trim down any material that the
flush cutting saw didn’t get. To be on the safe side, I will
trim the endwedge a little bit shy of the surface. Any gap
that results from this will be removed later
when I add binding.
Notice how I handle the chisel in a way that keeps the
chisel’s edge away the endblock so I don’t mar that
surface.

Okay, the endwedge is ready for it’s debut. I take the
sides out into the natural daylight and rub mineral spirits
on the area. Mineral spirits roughly mimicks the
effects of finish so you can get a glimpse of what
the end product will look like.