Chiefwoodworker's Blog

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 hardware and glass are on order and as soon as they arrive I will attach them. Then it is a simple matter of applying finish. For this clock I am going to use Min-Wax Wipe-On Poly Satin Finish.

Often, in the documentation of shop drawings or the creation of architectural views, it is necessary to create cross sections, especially when working with 3D models. Google SketchUp provides a very useful tool bar and tool set just for this purpose. It is a tool bar called Sections and you can make it viewable by going to View/Toolbars/Sections and checking it.

However, SketchUp has a minor flaw due to the fact that it is not a solids modeler like AutoCAD. When you perform a cross-section in SketchUp it is like cutting a shoe box in half; you can see inside the box from two openings. However, when cross-sectioning a building or a piece of furniture you are cutting through solids and what you expect to see are more faces like cutting a solid block in two. To fix this problem I suggest you download a Ruby script called SectionCutFace.rb. After following this link save the file as a text file with the name SectionCutFace.rb. Note the .rb file extension. This file must be a text file and it must have the .rb file extension.

This tutorial takes you through an explanation of the use of the Sections tool bar and context menu, as well as the use of the SectionCutFace Ruby script. I use a Side Table model as the vehicle to demonstrate their use. You can download this model from my Free Plans page and experiment with these tools on your own. Have fun!

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, 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. Tuesday of this week I will be out to the wood yards picking out the figured wood for the back. After that only mounting hardware and applying the finish remains.