Shaker Style Chain Driven Wall Clock
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
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.
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:
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.
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.
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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