Chapter
Nine

Fitting
the Major Parts Together

Up to this point I have covered the
work that goes into fabricating the three main parts of the harp - the neck,
the pillar and sound box.
This section explains how to join those parts together – an
exciting part of the building process.

I will detail two of the methods I have
used to join the neck and pillar to each other.   Then I will outline the process of
fitting and attaching the neck/pillar assembly to the sound box.   Finally a template for strings
will be positioned on the soundboard and the holes for the strings drilled
through the string ribs.

Many
traditionalists use a mortise and tennon to join the neck to the pillar.  To keep the neck from capsizing, the
mortise has to be deep and fit tightly.   For many designs, the shoulders of
the tennon have to be cut along an angled curve, and it took me several hours,
tears and some swearing to make a tight joint capable of withstanding prolonged
strain.

I found two
alternatives that were handsome and easy to make using tools common to most
wood shops.   The double spline
joint was my own invention, and I have adopted it as the easiest, fastest way
to join the neck and pillar together.    I came across the doweled
joint as I assembled one of the kit harps that Steve Green used to make.

Splined Neck/Pillar Joint

In this joint, two hardwood splines are
used in saw kerfs to join the neck and pillar together.

The basic steps are

1.
Lay out the joint

2.
Join the faying surfaces dead flat

3.
Cut the Spline slots on the table saw

4.
Fabricate Splines with the grain
running across the width

5.
Place two “clamping screws”

6.
Do a dry run, Glue the joint

First step - Laying out the joint

There are a couple of different ways
this joint can be laid out.  Some
are easier than others.

I generally lay out a mitered joint
running from the tip of the pillar to the inside corner where the neck and
pillar meet (See A).  This minimizes
the amount of exposed end grain and provides a little more surface area for the
joint.  They tell me the old Lute
makers considered exposed end grain to be unsightly, almost indecent.   B shows how the same joint would
look on a high headed gothic harp and a radius on the inside curve.   The joints can be run horizontal
and vertical as shown in C and D.    If you are going to do this,
think a little about how the neck and pillar are going ride on the table saw
when you are cutting the slots for the splines.  Also note whether the slot for the splines
will overlap any of the bridge pin and tuning pin holes.

Second step - Join the Faying surfaces dead flat

I
use a big horizontal edge sander to make the faying surfaces flat.  You can do the same with a jointer, but
you will need to feed the .  pillar
with the foot pointing forward and up, and the neck with the knee block
pointing forward to prevent tear-out.
As I machine them flat, I place the two pieces in position on a
workbench and check to make sure the distance from the tip at the foot of the
pillar to the corner of the knee block matches the length of the
soundboard.  Making small
adjustments to the faying surfaces between these parts can add or subtract an
inch between these points.

Third step - Cut the slots on a table saw

When I use this joint, the neck and the
pillar of the harp are the same thickness.
If your design is different, you will need to do some thinking in order
to compensate for the overhang.

I set the blade 1” high and set
the fence ¼” from the edge of the blade.  I find it easiest to fee the pillar
through the saw with the foot last.
When I cut the corresdponding slot on the neck, I fee the neck with the
knee block passing over the blade first.
This will ensure that outside face of the neck and pillar ride along the
fence.   When I don’t do
this, the two faces may not be even once the joint is assembled.   It is a pain to have to sand both
sides down so they are flat.

Once the first set of slots is cut, I
move the fence to cut the second set of slots.  I set the fence by turning off the saw
and rotating the neck around so the saw blade is in the slot I just cut.  Then I push the fence lightly against
the neck and lock it into place.
The splines both end up the same ¼” in from the face, which
makes for a clean, symmetrical look.

Fourth Step - Cut
the Splines

It is important to cut the splines with
the grain running across the width of the spline.  It is tempting to rip the splines
lengthwise, but the splines need to resist shear along the line of the joint and
carry tension between the neck and the pillar.  The splines need to be strong, so I
usually make them from a wood that is at least as hard and strong as the neck
material.

The splines need to be 2” wide,
so I cross cut a 2” block from the end of a board.    Before I cut the stock I
sight across the face of the board.
Any cupping in the board is going result in a wandering cut or a spline
that is too thin in the middle.  I
use a big belt sander make faces of the block flat.

At this point, the splines could be cut
with a table saw, but it is a problematic cut (at best).  The blade has to cut up through the end
grain, and even a new sharp blade will burn and scorch quite a bit.  There is also a tendency for the spline
to drop into the slot around the blade.
If you insist on going with the table saw approach, use a zero clearance
table saw insert, a finger board and push stick.

It is quicker and more precise to cut
the splines of the block with a band saw then sand them flat on a thickness
sander.  I make the bandsaw cut a
millimeter or two thick, returning the block to a jointer or sander to keep one
side of the spline flat.  After I
have cut the block into splines, I feed them through the thickness sander till
the fit neatly into a test block that I have cut on the table saw.  Ideally, the splines should slide into
the saw kerf with little play.

Fifth
Step – Place the clamping Screws

This is not an easy joint to clamp with
conventional clamps.  I tried
various clamps and other tricks, but found the best was to use two #6 x1”
screws, carefully placed and a single Quick Grip™ to clamp the joint
together.

When joints are covered with wet
adhesive, they usually want to slide around.   If you can get the clamping
pressure perpendicular to the joint they won’t slide around as much.  If you center the clamping pressure over
the joint, you will get more even pressure too.

I measure the mid point of the joint
and strike two perpendicular lines from that point along the joint line.   Then I drill two pilot holes for
the screws in line with the lines I struck.  I use one of those one handed Irwin
Quick Grip™ clamps with the rubberized pads removed to exert pressure
directly on the clamps.

Sixth Step - Do a dry run, then glue
the joint

I do a dry run with the splines in
place.  Epoxy only requires moderate
clamping pressure and fills any unwanted gaps.  I hold the pillar in my bench vise and
assemble the joint after I have coated the slots, splines and joint with
epoxy.  After the parts are
assembled, the single 12” Quick Grip™ clamp secures the joint and
allows easy access around the joint to clean up the excess glue with a paper
towel.   I try not to disturb
the joint till it has cured.

Doweled Neck/Pillar Joint

The second type of joint is more work,
but produces a more traditional-looking result.   The joint is created by drilling
three precisely spaced, parallel holes into the bottom of the neck and top of
the pillar.   In hard maple
this requires a guide block, a 10” long 5/8” brad point drill bit (from
Woodcraft) and a rugged drill motor.

Before drilling the holes,
realize the stress on the joint is asymmetrical - the dowels will  not centered in the joint, they will be
offset to the side in tension, the side furthest away from the strings.

The first task is
to create the jig – to drill three long parallel bores (holes) to guide
the bit.  It is a lot easier to make
those bores if you start from the center with three perfectly straight, parallel
“pilot holes” that are cut with a table saw.

(1)
Three shallow kerfs are cut on the face
along the length of a ¾” x 4” x 8” hardwood board,
spaced one inch from each other.

(2)
Another 4” x 8” board is
glued onto the bottom of the first board.
A thick clothes hanger wire can be run in and out of the kerf, pushing
most of the glue out.

(3)
After
the glue cures, I use an ancient but powerful ½” industrial
Rockwell drill (Rocky) equipped with an extra long 5/8” brad point
drill.  The kerf keeps the bit
centered during the bore.
Sight down the drill to ensure it is parallel to the face and edge of
the board.  One sure way to make
a hole wander off center is to push the drill too hard so that chips jam up the
tip.  Let the bit cut the wood,
don’t force it.  Back the
drill out frequently (four or five times) to clear the chips.  I even clamp the drill to a ceiling
joist so gravity helps move the chips out of the hole.

(4)
After the three bores are complete, I
use a bevel gauge to transfer the angle from the top of the pillar to the jig
and cut it into two halves.  Label
one half of the jig “Neck” and the other half “pillar”
so you don’t mix them up when it the time comes to drill holes for the
dowel.

At this point, I measure the length of the sound box and
position the neck and pillar pieces so they will fit.  This usually entails scribing and
sanding the top of the pillar so it closely follows the contour or the
neck.

After the joint is nice and tight, I am ready to use the
jig to drill the holes into the top of the pillar.   I clamp the pillar to my bench on
top of a 4x4 timber that has been joined dead flat.  I leave about 4” of the timber
extending beyond the pillar and clamp the jig block to that.   These old Record clamps generate a
lot of pressure, so I use pine blocks to keep them from marring the pillar or
guide blocks.

Drawing witness lines will help
position the dowel holes precisely.
Remember, the dowel holes should not fall in the center of the pillar;
they should be offset to the side of the joint that is in tension.  Study the cross section diagram at the
top of the page and the picture titled “Glued up and ready. .
.”  at the end of this section
to make sure it is set up right.
The edge of the dowel hole should be fairly close to the outside edge of
the pillar.

“Rocky” boring the second hole
in the pillar

As you bore the hole, remember what
makes bores wander off center.  Take
it slow, and back the drill out frequently to clear the chips.

The hole should be at least 2
½” deep into the pillar.
After the first hole is drilled, insert a 5/8” dowel to ensure the
jig stays in place while drilling the next hole.  The dowel should fit snuggly.

Drill the second hole and insert
another dowel. Then drill the last hole.
Repeat the process with the neck. In this photo you can see the witness
line on the neck that I used to

align with the edge of the drilling
jig.

Repeat the process with the neck. In this photo you can see
the witness line on the neck that I used to align with the edge of the drilling
jig.

Then I cut three dowels and fit test
the fit of the two pieces.  Here one
of the dowels is too long and needs to be cut shorter to allow the joint to
close up.

Gotta
have groovy dowels :

The dowels
need to have grooves cut into the sides to allow glue to escape during
assembly.  If the glue does not have
an escape path, the dowel/hole turns into a little pneumatic cylinder that will
either prevent the joint from closing or will split the neck or pillar.  Here, three grooves are cut along the
length of the dowels with a band saw, using a chunk of wood with a 5/8”
hole in it.  The grooves could also
be cut on a table saw, router table, a V gouge or Dremel tool.

Assembly
and Clamping

When clamping the neck and pillar, the
two should be brought into compression with the clamping force centered over
the dowels.   This isn’t
instantly achievable with most neck/pillar configurations.  Take a few minutes to fabricate a cap
piece and a fixture I call “The Sock” (because it slips over the
foot of the pillar), and the final gluing and clamping should be anxiety
free.

Glued!                          Top
detail,                  “The
Sock”

“The
Sock” is built from two 6 x 14” rectangles of ½” ply
or chipboard and three blocks of scrap wood that are just a bit thicker than
the pillar.  The glue blocks are
sandwiched between the two pieces of ply.
I glue the blocks into place and follow up with four 1¼”
ring nails into
each block, two from each side.

Once the
sock is built, do a dry run to make sure everything slides together easily
and the clamp is adjusted and can compress the joint snuggly.  If there are any gaps in the joint,
carefully sand or rasp the high spots.

Once you are
assured of the fit, glue the joint together and clamp it tightly.

After the
neck and pillar have been permanently joined to eachother, they need to be
fitted to the sound box.

Fitting the Neck/Pillar to the Sound box

There
are several creative ways to fit the neck and pillar to the top of the sound
box.  One of the simplest (and most
popular) is to use some kind of radiused neck joint.   With this joint, a radiused block is
added to the top of the sound box, and a corresponding curve is cut into the
bottom of the neck and knee block.  As the frame of the harp bends under
strain, the joint remains tight.  If
you give some thought to an artistic knee block design, it can look pretty good
like this Dusty.   Some builders worry about the neck
sliding off to one side or the other, and will use a pin on the top of the
sound box along with a goove cut in the bottom of the neck to limit its motion.

I prefer the more traditional approach which
is to use a flat joint and two 3/8 dowels to fix the neck in place.    It takes some skill to precisely machine mating
surfaces so that they will close up tightly once the harp is strung.  When the neck and knee block are neatly
carved to fit the top of the sound box it, presents a sinuous continuity that
cannot be replicated by the simpler radius joint.

When I build the sound box, I angle the
top so it will be perpendicular to the strings.  The keeps this joint in pure compression
(no shear) and the dowels simply keep the parts aligned.  If it becomes necessary to take the harp
apart for repairs down the road, it is a royal pain to pry this joint apart.  Some builders glue this joint, but
realize that repairmen will be cursing you long after you are in your grave if
you do so.

On the first fitting the neck will
rarely sit flat on the top of the sound box.

In
a perfect world you would actually want a 1/8” gap on the side towards
the strings (see detail).  As the
string tension is brought, up and the neck bends, this gap will close right
up.   You can achieve this gap
by trimming the bottom of the neck or top of the sound box.

Align
the front edge of the knee block with the top edge of the sound box.  An 1/8” gap on the side closest to
the strings will close up as the string is brought under tension.  It is best to leave the knee area larger
than the pattern till fitting it to the sound box, and trim it when you do the
final shaping of the knee.

Holding the shell into
place - A simple block is cut from a 2x6 so it fits the back of the shell.  The block is clamped to the workbench to
steady the shell while the neck and pillar are fitted. It helps to attach the
feet to the sound box to give it better stability too.

The fit is usually pretty close, and I
fine tune it by noting which side needs to be trimmed and using a stationary disk
sander equipped with a cast iron table to refine the angle.  Before I discovered the stationary disk
sander trick, this I used a router to machine this surface flat and at the
angle I wanted.

If you don’t have a disk sander,
use the router.  Clamp the neck
upside down in a bench vise between two boards which extend above the
neck.  Build a tray for the router
that rides on those two boards and mount a straight bit into the collet.  Check the clearance between the router
and the front and back edges of the knee block and re-adjust the angle of the
neck in the vice so the bit just barely clears the low side and will remove
about 1/8” from the side that needs trimming.

<pic of router in tray, neck clamped
into place>

The
rectangular boards on either side of the neck are ripped to the same width and
ride on the guide bars of the vice, providing two parallel edges for the router
to ride on.

After
I am satisfied with the fit between the pillar and sound box, I drill the holes
into neck, trying to miss the dowels reinforcing the knee block.  I drill corresponding holes into the top
of the soundbox using centerpoints to locate the holes.  For a five octave (36 string harp) I
usually use two 1½ x 3/8 diameter dowel pins to hold the neck
together.  If the neck joint is not perpendicular
to the strings you will need to use much larger dowels, or steel rod to keep
the dowels from shearing.

Right - I use a jig block
to ensure the holes are drilled perpendicular to the surface of the neck.

Left
- I use dowel transfer points on the top off the sound box to prick two marks
into the underside of the neck

After this joint is completed, I push
the neck onto the dowels and check the foot of the pillar to ensure it sits
flat against the string rib.   If
it does not, I scribe the foot of the pillar so I can trim it to rest flat on
the string rib.

The foot of the pillar will naturally
want to pull to the left side of the string band.   As you center it, you will make
the neck lean away from the strings.
I used worry about this and carefully worked out joints that had a 1-2
degree angle between the neck and pillar.
To my dismay, I found the string tension usually made the neck start
leaning too far towards the strings – the strain is enough over time to
make the pillar bend.   I make
the pillar joints straight now, and after the harp has been up to tension for a
few months the necks are just about vertical.

Attaching the foot of the Pillar

This will vary with the design.   For Medium and high tension harps,
I usually bolt the  foot of the
pillar through the string band, driving the bolt from within the sound
box.  With a 3/8 x 2½  inch lag screw.

Cutaway view of the bolt
securing the foot of the pillar.  It
is much easier to insert the bolt and tighten it with a ratchet wrench if the
bolt is higher, up off the floor of the base, entering near the
“heel” of the pillar instead of the toe.

In
some designs, there is no room to start the bolt, so I cut a 3½”
diameter access hole into the base of the sound box to facilitate this.

I
drill a ¼” hole into the foot of the pillar.   To ensure the bolt will not split
the foot of the pillar when it is bolted into place, I clamp the foot tightly
and drive the bolt in and out – effectively cutting threads into the hole.

I place a center point into the hole
and put the neck and pillar assembly into place.   I center the foot over the string
rib and press the center point down.
I remove the neck/pillar assembly and drill a 3/8 hole through the divot
left by the center point, through the soundboard and string ribs.

If the harp is a round or stave back
harp, I sculpt the knee block to fit the top of the harp at this point.   I use a band saw to hog off the
corners of the knee block and neck.
I attach the neck/pillar to the sound box with the dowels and use a strap
clamp over the top of the neck and under the sound box to hold the neck firmly
in place while I finish rounding it off.
I use a 4” power grinder with a carbide whisker grinding disk to
refine the shape.  The final
rounding is done with a hand rasp, orbital sander and scraper.  It can take a half hour or so but the
sculpted result is always well worth the effort.

After the
dowels at the knee block are in place, the foot of the pillar is pinned to the
sound box, and a strap clamp wrapped over the neck and under the base of the
sound box to simulate the string tension that will hold the parts firmly
together once the harp is strung.
The harp can be firmly clamped in the workbench vice while shaping the
knee block and neck.

With the thin veneer on a roundback,
you have to be very careful not to sand through the veneer when sculpting the
neck to fit.  I place a strip of
veneer or masking tape around the top of the neck.  When the my sander begins to abrade the
tape away, and I know it is time to change the angle or stop so I can finish
the job with hand sanding.

Drilling the Holes for the Strings in the
Sound Board

I find it easier to atone for earlier
inaccuracies by drilling the string holes in the sound board near the end of
the process.    If the
shortest string is supposed to be 4.25 inches long, I add 1/8 inch (for
compression strain) and measure down from the top bridge pin hole, mark that
spot on the string rib or sound board.   I also place a mark about
5/8” of an inch above the pillar on the string rib band.   This marks the lowest position an
eyelet can be placed for the bass string.   I remove the neck and pillar one
last time and position the template for the eyelets along the center of the
string rib, then use a center punch to mark the eyelet locations.

<pic showing the template in place
and marking the eyelet holes>

I then use that mark to position the
template for drilling the rest of the sound holes.   My plain twist bits are sized by
32nds of an inch, and some eyelets from different sources are a little over or
under the nominal size stated, so I'd suggest trying the eyelets in holes
drilled in scrap.  Punch the hole
position with a center punch, then drill, changing sizes to accommodate the
strings specified in the string table.    For wound strings, you will
need to ensure the eyelet’s inner diameter can accommodate a string and
the knot securing the outer wrap.

If the eyelets do not fit into the
space provided, it is usually best to fudge the bass strings closer or farther
apart.   In most designs the
treble strings are usually near their breaking point and changing the eyelet
position will make the strings too short (giving poor tone) or too long
(leading to breakage problems).
Changing the length of a bass string by ½” is less of a
risk.

This is a major milestone in the
building process.  The harp is now ready
for finish sanding and painting.

Copyright ©
2007, Rick Kemper

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