Woodworking for the handy, and not so handy
Large Post Caps, by hand
Lacking a sophisticated CNC Machine should not be a deterrent to producing quality, high accuracy pieces in a normally equipped shop. The capabilities of standard shop machines are vast when some simple problem solving is applied in order to stretch the limitations of our stationary tools.
Safety is always paramount when using these otherwise benign devices, particularly when they are used in creative ways or in operations outside normal operations for which the tool was designed. I cannot emphasize enough a rigorous attention to safety when stretching the boundaries of these machines.
So, to the matter at hand. A client requires post caps to be applied to the top of the posts of a fancy banister system in a high-end new residence. The first issue is that they are large, 7½" x 7½" x 2" tall. Large in the sense that anything larger than 6 inches usually exceeds the range of most standard shop tools when making such shapes. These are relatively simple, and the details below their level at the top of the post will add to the complexity if the overall design.
The material is Poplar, a relatively soft, stable wood that machines well and takes nicely to paint. Because of the size, I cannot use my usual method of shaping the four-sided pyramid with my Kapex chop saw. The fact that the top surfaces cannot be end grain, as they would be if the detail were to be applied to a fence post top, the basic shape is cut first, a block 7½" x 7½" x 2".
This is done with the chop saw. As the Poplar plank came in rough form (2½' X 10"), I first planed the plank to about 1/16" over the required 2" to leave some material for fine-tuning. Once that is done, I chop the rough blocks to about 8" x 8", then use the table saw to finish the sizing, leaving just a bit more than 7½" for sanding, etc. The table saw ensures a near perfect square when two sides are ripped with the same fence setting. Any variance from absolute equal sides will make the symmetry of the pyramid planes off and the ridges will not line up at the corners. Using scrap lumber, make at least one or more sacrificial blocks for use later.
Once the basic shape, plus a little, is accomplished, I then rough-cut the pyramid planes using my large band saw. I run a MiniMax MM16 for this operation. It is a very strong, accurate machine and the setup is meticulous. I have a shop-made auxiliary tall fence, which I use for larger material to ensure true perpendicular feeding. It clamps firmly to the table, outboard of the blade at just over ¾" from the blade to the fence face.
Finding the correct angle of tilt is done by this process: Using the 3D graphic program, Sketchup, I make an accurate full scale drawing of the block and then draw the angle represented by a line drawn from a point ¾" above the bottom of the block to the midpoint of the top. Using the amazing capabilities of Sketchup, I then determine the degree of that angle. The band saw’s gauge is only approximate, but the info from the drawing gives me a reliable ‘ballpark’ to start from.
Then I ‘eyeball’ the table tilt to get it close. Then, with the block vertical, bottom on the fence, I make some test cuts with the sacrificial block to hone in on the desired angle. Move the block slowly, keeping it firmly on the fence and make the four cuts of the pyramid.
Now, with all fingers intact, we have a rough representation of our cap, but the planes of the pyramid are rough courtesy of the band saw blade. Cleaning those up is a bit dicey.
I have an 8" jointer that is carefully fine-tuned for parallel table planes. I adjust the feed side table to just below the height of the stationary table, so that it just shaves the blade marks from the wood. It may mean more passes, but you want to work carefully toward the goal of all ridge lines meeting precisely at the corners and the apex. Variations from this will be apparent and ruin our effort. I rotate the block, doing a single pass on each side until the all surfaces are smooth. This may require some finesse and time, but the result will be a finished product that matches the requirements precisely.
Again, make sure that during all these steps your body is in a comfortable position as you stand over your machines and the settings are cinched down nice and tight. Keep a firm hold on the piece as you encounter the blades and really familiarize yourself with the motion required to achieve a smooth, solid pass each time.
Happy, safe milling!
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