The Finished Clock
This
clock is a wall clock, sometimes referred to as a
grandmother clock, but the latter name is not used
when referring to a Shaker style clock. Its overall
dimensions are 52" tall by 14 1/2" wide by 9 3/8"
deep. The height is driven largely by the mechanical
movement. Since this is a chain and weight driven
eight day clock, sufficient height must be provided
in the pendulum compartment allowing the weights to
fall the required distance to last eight days.
The clock carcass is cherry
and though not visible is constructed with hand cut
dovetail joinery. The back of the pendulum compartment
is spalted maple which gives this relatively large area
some interesting figure for eye appeal. To provide
contrast the doors are made of walnut.
In keeping with the Shaker theme the trim is simple
bullnose and quarter round. Door pulls are turned
"mushrooms" typical of what the Shakers
would use.
The
clock dial was drawn using Google SketchUp. The four
I's to represent the numeral four is not a mistake.
Though four is correctly represented as IV it is
traditional in clocks to represent it as IIII.
After drawing the clock dial in SketchUp I applied
an antique texture behind the numerals to add a little "age".
Next I printed the dial full scale on 13" X 19"
premium card stock. To protect the dial I applied seven
coats of Spray-On MinWax Satin Polyurethane with the
added benefit of still more aging (it dries slightly
yellow). Finally the card stock is glued to a plywood
backing. - Did he say plywood? Yes, an extremely rare
occasion when I use anything but hardwood in my projects.
To complete this project I used non-mortising hinges
and rare earth magnetic catches. The hinges have an antique
brass finish. To keep the clock level in the vertical
direction I used two adjusting pins that have sharp
points which dig slightly into the wall and can also
be adjusted for level in the orthogonal vertical plane.
These pins are made especially for this purpose and are a
traditional piece of clock hardware. I finished this piece
with seven coats of hand rubbed MinWax Wipe-On Polyurethane
Satin Finish.
If you wish to build this clock you will find
SketchUp plans on my
Free Plans page.
The Mechanical Clock Movement
The
mechanical clock movement is a German made
Hermle model 241-080. It is an 8-day movement
with a gong that strikes once on the half hour
and counts out the hours.
The
pendulum is 34” long from the dial center to the
bottom of the swing. Hence, the clock case is rather
long, 52".
Most
clockworks suppliers will tell you not to design or
build a case until you have all hardware in hand
(clock movement and other pieces). There is a good
reason for this sage advise. The only installation
instructions you receive is something akin to the
picture shown at right. Click
on the picture to enlarge it and see the skimpy and
ambiguous information
provided. The first question I asked myself is what
is meant by 7 1/2” swing? There are are lot of other
questions, like how big is the bob? How far back
should the movement be from the plane of the dial?
What cutouts are needed on the seatboard? How do you
mount the movement to the seatboard? The questions are many,
and the only way to get answers appears to be reverse
engineering. So I quickly ordered the movement and
documented as many measurements as I could.
Fortunately,
I draw my plans in 3D using SketchUp. So I made a
couple of quick drawings to get answers to the first
question – what is meant by 7 1/2” swing? I figured
there are two possible extremes, a wide swing shown
in the SketchUp drawing at left, and a narrow swing
shown at the drawing at right below.
I called the company I purchased the movement from and asked for a PDF
or some other documentation. They essentially said, sorry, there is none to be had. An exhaustive search on the Internet for a PDF file failed. Fortunately, with the help of AllExperts.com I was able to reach a clock expert. AllExperts.com put me in touch with Charles Barrett of Die Klockwerken Antique Clock Repair & Restoration. Charles was able to answer all my questions which are listed below:
- What is meant by 7 ½" swing?
I assume it means if the case is more than 7 ½" wide (e.g. 8" or more, it should not interfere with the bob.
- Do the weights fall below the pendulum for an 8 day period? If so, how room should I allow?
- How do you attach the gong so that the hammer (one hammer) can strike it appropriately? Can it hang from a board or will that kill the sound?
- How far back should the movement be from the plane of the dial?
- What cutouts are needed on the seatboard?
As I suspected, 7 1/2" swing was the minimum
distance of the internal wall required to make sure
they did not interfere with the pendulum. Charles
recommended at least 8". Since my dial is 10 1/2"
wide which dictates the inside width of the case,
there is plenty of room.
Another important question whose answer dictates
the case dimensions is how far the weights must fall
to provide full eight day clock operation. The
skimpy information provided on the suppliers website
says the pendulum will hang 34" from the center of
the dial. But do the weights fall below the pendulum and how much? Charles answered this way:
"The weights can fall below the pendulum and usually do for a 8-day run but it is hard to say just how long the critical length of the case drop should be to match the full 8-days. Reason being, is that it depends on the length of the weight shells. With that said, I would compensate a full length and a half weight shell length for max case length to achieve a full 8-day run."
 The weight shell length I measured to be 6" which suggests the inside bottom of the case floor should be at least 34" + 9" or 43" below the dial center. I decided to make the case height 52" to accommodate this requirement.
I still hadn't figured out how I was going to mount the gong. As you can see from the picture it is a coil style gong. Charles answered question three as follows:
"Is the gong a coil gong or a rod type? In either event, be SURE that the gong is attached to the most dense part of the case (best if it is attached to the backboard of the clock case and be sure to use a REALLY solid hard wood for this since the mounting point of the gong is going to act as your sounding board.
The hammer strike point should be 1/4 to 1/6 of the length of the rod where the hammer strikes the portion of the rod CLOSEST to the mounted end of the rod--NOT the free end of the chime rod.
If it is a coiled gong, have the hammer strike the INSIDE portion of the flat portion of the coil closest to the mounting point."
Question four I answered myself once I took careful measurements of all the important points. Also, I am using a 1/4" backer board, called Dial Mount in my design drawings, which is different than just using the Clock Dial that came with the clockworks. But for reference here is what Charles said about the placement of the clockworks:
"The face should have come with the movement and is mounted to the movement by way of mounting pins on the back face of the dial that protrude through the front plate of the movement. When you close the door of the clock, be sure that you allow 1/4" clearance measured from the end point of the hour pipe so that it doesn't interfere with the glass door."
The seat board is a critical item in the case design. Get it wrong and the clock will not work or will not align with the center of the clock dial. Either is catastrophic. Charles described the cutout requirements as follows:
"Seatboard will have cut-outs for a. chains/cables, b. short cutout for the leader travel on the rear of the seat board closest to the backboard of the case, c. mounting hold-downs for the movement in relation to the threaded posts that connect the front and rear plates together."

Making measurements of the clockworks to precisely
place the cutouts is tricky because the posts connecting the front and back plates together are not symmetrical relative to the center of the hour pipe (the pin that drives the hour hand).
Nor is the hour pipe centered on the front plate.
Further, the gears that support the chains are not symmetrical relative to the hour pipe. I used the center of the hour pipe and the front side of the front plate as reference
datum for the clockworks and the intersection of the center line and top front edge of the seatboard as reference
datum for it. After careful measurements, and allowances for tolerances, I came up with a seatboard
design as shown.
I
needed to assure myself that the internal case width,
depth and height in the upper movement compartment could
accommodate the required placement of the gong. I could
either build a mock up and completely assemble the clock
works, or I could create a SketchUp model of the gong
wire and gong support. I decided that creating an
accurate model has many benefits. Since the entire
design is done in 3D, a 3D model of the gong wire and
gong support would allow me to place it, then move it
around until the desired position is obtained.
The above picture shows the gong wire, gong support
and the movement with the bendable wire and adjustable
hammer. Click the picture to get an enlarged view. The
gong wire is essentially a spiraled wire. To create this
model in SketchUp I created a path using the Cubic
Bezier Curve tool (see
My Favorite Ruby Scripts if you do not have this
tool). But first I had to create some guide points to
follow. I did this by starting with a circle of a radius
equal to the outer radius of the physical spiral. I
wanted to create seven spiral loops. I measured the
distance between spirals and used that as a distance the
radius had to shrink on each loop. Dividing this by four
to get the decrement, I then started at the outer radius
and continued to rotate clockwise placing a guide point
at each 90 degree point with the radius at each point
reduced by the decrement amount until I had seven
spirals.
Next,
at the outermost end of the wire I created a circle
whose plane was normal to the path (curve) at that
point. Then using the Follow-Me tool I created the gong
wire. One problem with this technique using SketchUp is
that SketchUp does not do well when dimensions of
surface triangles are small. To overcome this you can
scale all dimensions up, create the model, and then
scale it back down - or you can opt to manually clean up
the results you get without scaling. The picture at
right is the finished model. To get a model that appears
smooth you may need to use the Eraser tool with Ctrl to
hide and smooth edges.
This allowed me to complete the case design and
accurately place the gong wire and gong support.
Clocks are tricky things and this one has been made trickier than normal because of poor documentation.
Let me restate that - no documentation. But I used SketchUp to model the gong wire and gong support,
printed out a full scale version of it, and then I was able to experiment with placing it in the model.
If I had to do this in the shop using mock-ups it would have taken me some time and frustration
I wasn't willing to spend or experience. Ahhhh! Good old SketchUp comes to the rescue again.
The 3D SketchUp model of the gong and seatboard is shown at right. Unfortunately this placement required me to deepen the clock case more than I wanted to. I thought I could find a position where the gong wire would be in the vertical plane. However, that would require excessive bending of the hammer wire, more that I wanted to gamble on. So the compromise was to deepen the cabinet.
The Clock Design
 Finally,
I was able to complete the case design. At left is a
rendered front view, and at right an isometric view.
Note the case is constructed using dovetail joinery. You
can see this by looking at the top after clicking on the isometric view to enlarge it. I always include hand cut dovetails in my designs somewhere. It's a fetish of mine.
Notice the room left in the case below the pendulum. This is to allow for a full eight days of operation. The weights actually fall below the pendulum in the last couple of days. There are no holes in the clock dial for keys to wind the clock.
Winding is accomplished by opening the lower door and pulling the weight chains so that the weights rise to their topmost position.
The upper door opens to allow for setting of time.
I have put the SketchUp model for this design on my Free Plans
page. Be aware though, that because of the detail I
employed in some of my components this file is rather
large (2.73 MB).
Now it is time to go to the shop and start crafting this puppy.
Of course the first step is to select then necessary
rough lumber paying careful attention to grain and color
and then planning, jointing and thicknessing to the
appropriate dimensions. I won't spend time on this step
but go right to dovetailing, my favorite joint.
Dovetailing The Carcass
I stared by preparing stock for the
sides, top and bottom. I cut all pieces to final overall
dimensions including thickness. When building a carcass
using hand cut dovetail joinery it is especially
important that all mirrored pieces (right and left side
for example) are precisely the same size and perfectly
square. Next I carefully choose the surfaces I want
exposed and then mark the material to be sure they go
together correctly. Carpenter’s Crayon is perfect for
this purpose.
A
hand cut dovetail joint requires quality hand tools.
Like all woodworkers who work with hand tools I have my
favorites and will stack them up against anyone else’s
favorites. It’s kind of a religious thing. My choices
appear in the picture at left. The dovetail saw, chisel
and dovetail marker are all Lie-Nielsen. The dovetail
saw is the progressive pitch model; it has fine teeth in
the front for easy starting and more aggressive teeth in
the back for rapid cutting. The dovetail marker has a
7:1 pitch (or approximately 8 degrees) which I use for
hardwoods, and also serves as a square to mark vertical
line for half pins. The chisels are just the right
length and well balanced. Their weight is on the light
side so that your fingers do not tire after hours of
dovetailing and unlike Japanese chisels whose triangular
top edge cuts into your fingers, the flat top edge of
the Lie-Nielsen does not.
I
like a light, hard rock maple wooden mallet. This one
was recommended by and purchased from
Nora Hall’s website. Nora Hall, if you don’t know,
is an expert on carving. A small engineer’s square is
ideal for marking the top edge with tail and half-pin
spacing. I cut tails first and cutting perpendicular to
the board face is critical for good fitting dovetails.
The dividers are Groz with sharp points and are used to
layout the pin and tail spacing by setting them to the
width of one tail plus one pin and stepping the divider
across the ends. Setting the dividers and marking other
critical dimensions is accomplished with an accurate
scale. I use the Incra Tiny T Rule which marks to 1/64″.
The Lee Valley Veritas marking gauge makes quick and
accurate work of scribing the pin and tail depth across
the grain. And finally a well sharpened pencil with lead
on the soft side for marking completes the tool set.
The
sides of this clock are 51″ long. Cutting tails on this
length piece can be quite a challenge. In the past I
would have used my
adjustable height bench raised to its maximum height to
secure the board to eliminate chatter while sawing.
With my new
Lie-Nielsen bench I find the face vice holds the
piece securely and its size and mass all but eliminate
chatter making tail sawing easy. I still needed to stand
on something for elevation. One of the stools
I wrote about crafting as Christmas gifts for our
grandchildren came in handy for this purpose. I
reposition it frequently so that my stance and arm are
appropriately aligned to make the cuts. I use this stool
again when removing the waste between the tails with the
fret saw as shown at left.
There are two aspects of cutting tails that is
critical to good joinery. The first I mentioned earlier
is cutting perpendicular to the face of the board.
Failing to do so will leave unsightly gaps, poor glue
joints and weak mechanical joints. The second aspect is
to stop the cut at the scribe line. Going past this
point will show and leave a sloppy appearance, not one a
craftsman wants to project.
There are a few aspects of tail cuts that are not
critical. The angle of the cut is nominally 8 degrees
from vertical, but this is not critical. Neither is the
width of the gap (pin width). Machine cut dovetails
would all be perfectly angled and spaced, but then they
would look machine cut. The human is not a machine. Hand
cut dovetails are beautiful precisely because they don’t
look machine cut; they are all slightly different,
adding to the beauty of the piece.
T
he
pins are a little more difficult. First, the pins are
traced from the tails by laying the tail board on the
pin board, aligning them perfectly perpendicular and at
the correct depth and tracing the pins from the tails
with a sharp pencil or knife. I prefer a pencil because
I want to saw on the waste side of the pencil marks,
that is, leaving the pencil mark which is actually part
of the pin. This I can see clearly with pencil marks.
However, a knife mark tends to draw the saw blade into
its kerf leaving me less control. I complete the layout
using the dovetail marker being sure to mark the waste
area with Xs as shown at right.
There
are critical aspects of pin cuts that must be adhered
to. Cut on the waste side of the pencil mark, but
aligned as closely to it, and along it as possible. Cut
straight down using the vertical lines as a guide. Stop
at the scribe line on both sides of the board. Paying
close attention to these will assure snug fitting
joinery - assuming you also cut the tails correctly. The
trick to hand cut dovetails is being able to cut
vertically and to follow a line. Once those two skills
are mastered you can hand cut dovetails that go together
the first time, every time.
It helps to cut vertically if your piece is mounted
in the vice plumb. The shoulder vise on my Lie-Nielsen
lets me quickly accomplish this by holding the piece
flush against the vice as I tighten it.
After
making all the vertical cuts I am ready to remove the
waste. This is done in two steps. First, clear the
majority of the waste from the pins by cutting it away
with a fret (or coping) saw. I twist the blade in my
fret saw to about forty five degrees with pliers. This
allows the saws frame to clear the board as I cut.
Turning it ninety degrees to the frame would make
starting the cut near impossible. When sawing I try to
stay as close as I dear to the scribe line leaving just
enough to support the chisel cleanup that will follow.
How much you leave depends on your experience and
courage. If you are just starting out stay at least an
eighth of an inch from the scribe line. Be sure you cut
evenly front to back. You don’t want to cut close to the
scribe line in front and below the scribe line in back.
Judge this carefully. After a while it becomes natural
and requires no special attention.
The
second step in clearing the waste is to clean up the
material left by the fret saw. I perform this step with
a very sharp chisel. Depending on how close I cut to the
scribe line will determine how many cuts along the
scribe line I will need to take. If you are doing this
and you leave a quarter of an inch for example, you will
want to make at least three passes as you approach the
scribe line. The last pass should be no more than one
eighth inch. Less is better. I hold the chisel slightly
passed vertical such that the waste is cut angled into
the board. The end grain serves no purpose in the
joinery; only the faces of the pins and tails are used
to form both the mechanical and glue joint. I check with
a small engineer’s square that the material is removed
such that the scribe line on each face is unimpeded by
material that might project passed them.
The
final joinery set is shown at right. Note that you can
still see the pencil marks on the pins. As mentioned
above they are part of the pin material since the tail
was used as the mask to form the pins. Also note that
the tails are cut perpendicular to the face of the tail
board and the pins are cut straight down - that is
vertical to the board. These pins will go together for
the first time during glue-up with no dry fit required.
I have a confession to make. You can see that some of
the end grain in the pin boards was chipped out. If my
chisel were as sharp as it should have been this would
not have happened. My chisel was sharp when I started
out on the tail boards and I should have stopped to
sharpen it for the pin boards. However it was close to
dinner time and I was almost done so I plugged along.
The small white sin here is that the end grain does not
play a part in the joinery and will not be seen. So I
can be forgiven, though it is not my usual practice.
There, I feel so much better now that I got that off my
chest.
If you are just starting out with hand cut dovetails,
or haven’t yet started but would like to, I would highly
recommend purchasing
Rob Cosman’s series of video tutorials. I have been
cutting hand dovetails for ten years now and consider
myself experienced. But I still purchase nearly every
tutorial I can to see how the masters do it so that I
can learn and improve. Frank Klausz is probably the
dovetail king with Rob Cosman a very close second, but
Rob’s videos I find to be the best tutorials on the
market. Don’t shy away from hand cut dovetails. Innate
skill is not required. Anyone willing to practice sawing
vertically and to a line can master them.
Milling The Seatboard
One of the more important components in a clock case is
the seatboard. The seatboard is the board on which the
clockworks is mounted and secured. Its placement
determines the vertical and horizontal centering of the
hour and minute shaft relative to the clock face. It
also determines the clearance, or depth of the shaft
relative to the clock face.
The
seatboard consists of a number of holes that must be
accurately placed. Two small holes are for threaded pins
that secure the works to the seatboard. When installed
in the clock the seatboard itself is fixed (no mechanism
for adjustment). The positioning of the works on the
seatboard directly affects all positioning mentioned in
the previous paragraph. So these holes too must be
accurate.
Since this is a chain driven clock there are four larger
holes that allow the chains to move freely and hang in
the pendulum cabinet (lower section of the clock). These
holes need to be large enough to permit “pulling” the
weights once a week for winding and to ensure no
interference as the weights slowly drop while driving
the clock.
One rectangular hole is needed to allow the pendulum to
pass through and swing. This hole does not require
critical dimensions, simply enough room for clearance.
As mentioned earlier the clock works for this project came with
no documentation. I had to reverse engineer the seatboard design by taking very careful and difficult
measurements of small, and deeply imbedded parts in the
clockworks. I am sure you are asking yourself, “How can
this be difficult? After all, there are only four holes
we are talking about”. Well, let me assure you that
positioning a 6” steel pocket rule inside the delicate
works of a chain driven clock to make accurate
measurements is all but impossible.
I
meticulously took measurements and used them to create
shop drawings. After milling my first seatboard and
mounting the works, I made further measurements to test
whether alignment in the final clock would be correct.
This resulted in changing the position of three out of
six holes.
I corrected the shop drawings, milled another seatboard
and tested again. This time everything worked out
perfectly.
Milling this component provided the first opportunity
for me to use my new Supreme Drill Press Table purchase
from
Peachtree Woodworking Supply, Inc. It worked like a
charm, allowing me to quickly, accurately and repeatedly
drill the holes. For the larger holes I used a Forstner
bit with a backing board to ensure no tear out of the
opposite side.
The rectangular hole was a three step process. First
I drilled two holes, near each end and inside the
rectangle, and large enough to accommodate a sabre saw.
Second, I used the sabre saw to rough out the rectangle.
Lastly I used scrap wood pieces and double sided tape to
form a a template for a template router bit to follow.
The completed seatboard is shown above.
Gluing Up The Carcass
 Like most woodworkers I never glue-up a piece without first dry fitting it. This accomplishes a number of things. First it lets me know if I need to trim a joint for fit. Second, it gives me a chance to practice the steps I will use in the glue-up, which uncovers all the tools and aids I will need, saving me from hunting down something while glue is setting up. Lastly, and most importantly, it helps me develop a glue-up strategy and sequence. Without this dry run a merely stressful step becomes a disastrous and disheartening one.
Most of the joints in this carcass are dovetails. I like to inspect them for tightness and gaps. I also check to be sure they seat completely. Dovetails will almost always go together smoothly if the pencil marks that mark the transfer of the tails to the pins are still visible. This is a check that can be made before the dry fit but it never hurts to double check.
Dovetailed carcasses are unique in that, while clamps are useful, and sometimes necessary to seat all the joints, clamps can be immediately removed. The dovetails are enough to hold the carcass while the glue sets up. This allows for easy checking and correcting for square.
 Even with all this checking and dry fitting mistakes can still be made. After I glued up this carcass I noticed one. I have marked the outline where a hole is supposed to be in the picture at right below. This hole is intended to allow the pendulum and weight chains to drop from the clockworks compartment to the pendulum compartment. I should have milled this hole before glue-up. Fortunately, while more difficult,
was still doable after the glue sat overnight.
Trial Assembly Of Clockworks
At this stage in the clock construction it was time to test the clock, pendulum and gong assembly to be sure no adjustments
were needed to the seatboard or gong block. Making any adjustments later would
be much more difficult. Also, I had been waiting for some time to hear the gong, not at all sure I would like what I heard once I heard it.
After a day of fiddling I managed to get the clock working. The main problem was that the clock would stop after five to ten minutes. The solution
was what clock masters call “putting the clock in beat”. This is a process of adjusting the slip clutch on a crutch arbor until the tick tock sound is balanced. The instructions call out components such as verge, crutch, clutch, leader, escapement and suspension spring. Being a woodworker I have never noticed any of these components in the shop. It was all new to me. But with some perseverance I prevailed and the clock
ran for more than a day.
The gong sounds great, though it is awfully sensitive to adjustment. A tiny bit left, right, up or down and the sound is totally different. So I decided not to glue the gong block in place until the clock is ready for finish. I even
considered an attachment method that would allow
position adjustments instead of gluing it permanently in
place. But in the end that seemed like overkill to me.
Milling The Trim
 The clock carcass is trimmed with a sandwich of
quarter round and bullnose pieces. This requires two
bits: I used a CMT Cove Bit #837.951.11 to form the 3/4”
radius quarter round, and a CarbTech Triple Beading Bit
#02-03 for the 1/8” radius bullnose. The Cove Bit has a
bearing which controls the cut into the side of the
stock. The depth into the face of the stock the
woodworker must set. With a bit this large I like to
make a few passes, increasing the depth on each pass
until I reach 3/4”.
The
CarbTech bit cuts three adjacent bullnoses, each 1/8”
radius. It does not have a bearing so you need to
account for its depth of cut into the stock’s side with
the outgoing router fence. I sacrifice the middle bead,
cutting the stock in two right down the middle; an easy
and safe task with a band saw. Next I use the drum
sander, loaded with 220 grit sandpaper, as a thickness
planer to finish the bullnose. A little glue and a few
clamps and we have our trim.
Since I planed all the stock before milling, used 220
grit paper in the drum sander, and used sharp router
bits, little or no sanding was necessary. Minor sanding
was done with 320 grit paper to remove the raised grain
resulting from glue clean up. I was very careful not to
destroy the edges that define the trim, and I performed
this sanding only after the trim had been applied to the
carcass.
Next I will apply the trim and build the doors. We
are close to completion.
Trimming The Clock
Trimming
a piece requires careful attention to the joints. Even
simple forty five degree miters can be tricky, sometimes
requiring hand fitting with a block plane. But the most
difficult part is cutting trim to the correct length;
too long it doesn’t sit tightly against the backing and
too short it leaves unsightly gaps.
I
like to start by cutting the front trim to length first.
To do that I cut the miter on the side pieces leaving
them long. I clamp then in place and then cut both
miters on the front trim, intentionally leaving it about
1/8” too long. I then sneak up on the correct length
with a series of very fine miter saw cuts. As I approach the
correct length I observe how the miters are coming
together, and, if they need hand fitting I take thin
shavings with a block plane and a shooting board. This
is the equivalent of the dry fitting process that
precedes all glue ups.
Once
I have the front piece cut to exact length I glue it in
place and clamp it. I let it sit for about an hour and
then go back and apply the side pieces. The side pieces
require special attachment because this is a cross grain
situation. Normally I would glue the first two inches of
the mitered end, and use a
sliding dovetail joint to hold the other end in place to
allow for seasonal expansion. See picture above right as
an example of a sliding dovetail trim attachment.
However, this piece has relatively narrow
sides, only 7 3/8” wide. Using a software tool to
calculate the expected seasonal change for the Western
Massachusetts area and cherry wood, I need only allow for about
1/8” expansion/contraction. Enlarge the picture at left
by clicking on it and you will notice that this
calculation is a function of stock type (flat sawn
verses quarter sawn), area of the country where the
piece will reside, current moisture content and species
of wood.
Since the amount of movement is small, and the side
narrow, I can use a simple elongated slot, screw and
washer to allow for seasonal expansion. See the picture
at right. Notice that I placed the screw toward the
right end of the slot because most of the hot humid
season was still ahead of us at the time of construction. I tighten the screw just
enough to hold the trim in place, but not too tight,
allowing the screw and washer to easily slide within the
slot.
After the glue dries I like to inspect for glue spots
that may have been left during the glue up process. The
easy way to do this is to wet the surface down with
mineral spirits. Mineral spirits does not raise the
grain like water does and dries quite quickly.
This
procedure also gives me a preview of what the wood will
look like once the finish is applied. I’ll again inspect
the entire piece this way toward the end of finish
sanding.
The completed and trimmed carcass can be seen at
right. The trim seems a little weird without the doors
in place but that will be resolved shortly. The slots
you see in the clockworks compartment is for a 1/4”
panel that will slide into place, and on which the clock
dial will be mounted. Both the clockworks and pendulum
compartments have backs. I selected a figure wood,
spalted maple, for the back of the pendulum compartment.
This shows nicely through the glass of the door and the
dark walnut of which the doors are constructed.
Crafting The Doors
The
doors of this clock are made of black walnut (aka
American walnut) chosen to provide contrast to the
lighter, and more red shade of cherry. Walnut, while an
excellent furniture wood, is not one I like working with
much. There are very few adverse health effects related
to walnut though there have been documented reports of
skin irritation, rhinitis and asthma. But the saw dust
generated by walnut is very fine and highly noticeable
even with the use of dust masks. I find its taste bitter
and unpleasant. So, while it is a beautiful furniture
wood I tend to use if for contrasting trim and doors and
seldom build an entire piece out of it.
Most
of the walnut pieces in this clock are short, about 12”.
So I have chosen to thickness plane them with my drum
sander and avoid the problem of sniping. I load the drum
sander with 80 grit paper. After joining and planing
three sides with a power jointer followed by a hand
jointer and smooth planes, I cut them to near length and
thickness them on the drum sander.
After
bringing the pieces to within 1/16” of final thickness
using 80 grit paper I switch to 220 grit for final
thicknessing. I don’t have to run through all the grits
in between because I am taking off more with the 220
grit paper than the depth of the groves left by the 80
grit paper. I would not suggest trying this with a
random orbital sander though.
The drum sander has many uses not immediately
obvious. For example, power planing a tiger or blistered
maple board will often leave tear out because of the
rapid grain changes. The drum sander is an excellent
choice for final thicknessing in this case. Also, the
safest way to taper legs is a drum sander. You might
first rough cut the taper close to the line with a band
saw and follow it up with a drum sander (see above
right), or skip the drum sander altogether. Either way
you avoid the dangerous step of either a table saw or a
jointer.
When
thicknessing is complete I cut a 3/8” wide by 1/2” deep
rabbet in all pieces. Normally I would do this with a
set of dado blades. But if I do this on the table saw
instead, the off cut pieces are exactly the size I need
to secure the glass in the door.
For this Shaker wall clock I have chosen simple doors
constructed with slip joints. This is consistent with
many Shaker clocks in existence. More importantly, for a
given rail and stile size, slip joints provide more glue
area and are stronger. The rails and stiles on this
clock are only 1 1/8”, so this added benefit is quite
important.
Slip
joints are basically a mortise and tenon with the
mortises being open. The table saw and tenoning jig make
cutting the open mortises and tenons easy and safe. I
cut the open mortises first and then cut the tenons to
fit. The jig has a fine vernier so that I can creep up
on the correct tenon thickness.
Two of the stiles for the long door are 37” long, not
a piece I would want to hold manually while guiding it
through the table saw. This jig is designed to hold them
secure, at perfect right angles, and hands safely clear
of the blade. It is heavy and tightly fits the table saw
groves so the cuts can be smooth and slow avoiding tear
out.
I
cut the tenons so they fit a little too tight in the
open mortises. Then I final fit them with a shooting
board and shoulder plane. This gives me a perfect
fitting slip joint. The doors are crafted over sized,
one quarter in wider on all sides. This leave me the
ability to custom trim them to the carcass. A quarter
inch may seem a little overkill, but it also allows for
a little tear out on the ends of the stiles and mortises
which will not remain after trimming.
The doors, after glue up but before custom fitting,
are shown above right. Notice the rabbet shown on the
back side of the long door. This rabbet provides and
inset for the glass.
Special Joinery For The Backs
The
backs of a custom piece serve a number of functions and
they are far from simple pieces of wood. The upper back
in this piece provides a mechanism for hanging the clock
while it also serves to keep dust out of the clock’s
works. The upper back is not, however, visible since it
is hidden by the clock dial.
The bottom back is visible, just behind the weights
and pendulum that drive the clock. It also serves to
keep dust out of the case. However, because the swinging
pendulum will draw all eyes to itself and the back, it
is important that the back not look like a plain piece
of wood, but rather adds to the beauty of the clock. For
this clock spalted maple serves that purpose. The random
black lines of the early fungus and the tan and greenish
color of the wood provides the viewer with an artistic
drawing that only nature could render.
Backs almost always require special treatment to allow
for seasonal expansion and contraction. In large pieces
I often use ship lapped boards that are spaced one from
the other to allow for seasonal movement. Theses backs
are not wide enough to accommodate this approach.
Instead, after calculating the expected movement, I cut
the backs narrow by 1/4” and fastened them with slotted
open holes, washer and screws. I cut them narrow because
expansion season has only barely begun, and at its peak,
the backs will expand to close the gap. If this were
peak expansion season I would have cut them to fit and
let them shrink to their minimum size. The washer and
screws hold the back flat but also lets it move under
the washer. I am careful not to tighten too much. Notice
that I center the backs so that the gap for expansion is
equal on each side.
The only remaining tasks to attach the finish, hardware,
glass, clock dial and clockworks. These are described in
the opening section.
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