Clock case assemblies are for the most part boxes. Whether rectangular in shape, or square, the housing for the movement is fundamentally the same. Take a tambour case for instance. Despite the arch cut top, note that the main case blank is basically a rectangle. We would begin with a rectangular piece of wood before we were to cut the arch profile. The base plate, which the tambour case is mounted upon, will also be rectangular in shape. We can determine that the tambour case will be made up of two wood parts, both rectangular in starting shape. Breaking an assembly down into core shapes helps you to determine the number of wood parts required and will give you rough dimensions to base the overall clock assembly upon. Remember to reference your movement dimensions and mounting requirements in this process as well.
We are now ready to convert our rough sketch to a dimensioned assembly sketch, and the drawing board is the best place to achieve this. The drawing board, or any computer related drafting program – if that is your preference, is the best way to determine overall finished dimensions for each wood part of the assembly. Note that you need not be an artist to proceed with a dimensioned assembly sketch. I prefer to draw a full scale front and side view drawing of the assembled case commonly referred to as an assembled elevation drawing. If you’re the drawing board type, I recommend having access to a good compass, an accurate ruler, a pencil, and a large eraser (even the most experienced drafters need to erase things from time to time). Access to drafting triangles and circle templates can also be beneficial although not required.
Begin with a vertical centerline and base dimensions of the drawing from this line out (left and right). This will help ensure accuracy. Draw the clock design at full scale (1 inch = 1 inch) using your overall rough dimensions as a guide. If the overall tambour clock assembly is 4-7/8” in height, for example, then I use this as a parameter to work within. I require two wood pieces (body and base) and would like to keep the base at ¾” thickness. This means that my clock body height can be no more than 4-1/8” if I still wish to retain an overall height of 4-7/8” for the assembly.
I will even go as far as to provide a full scale outline of the mounted movement based upon overall dimensions acquired from the movement. This is a nice way to illustrate how the movement will fit within the case and is recommended for both front and side elevation views.
During the final drawing process, you may also determine what types of edge treatments you would prefer for parts. Decorative edge treatments such as coves, ogees, beads, (etc) can help you achieve a unique and stately profile that will add accent to the overall look of the clock assembly. You can reference router bits from your own personal collection or you can reference numerous router bit supplier catalogs for profile options. Note that most suppliers will list specification information for each bit which will help you to dimension the resulting profile for your full scale drawing. It is good to remember that some dimensions of the clock case drawing whether length, width, and/or thickness may need to be adjusted to best suit desired router bits.
Always keep in mind that the design process is trial and error, and there are no set rules or guidelines with how one should proceed. While the suggestions provided are merely my own preference for design, I have found that the creative process works best for people when they create on their own terms. Just keep in mind the four “handy” rules of thumb for sketch design work: 1.) If something does not work, erase it and try something different. 2.) If a profile does not turn out as pleasing as you would have desired, even after adjusting wood blank dimensions, simply grab the eraser and start anew with specifications from a different router bit. 3.) Always know where your eraser is. 4.) And, perhaps, the most important rule of all – – be creative, have fun, and don’t be afraid to experiment!