solid modeling and woodworking

What? What does a digital tool have to do with woodworking? Maybe nothing, but as I continue to ponder my time in Houston (see my last post), I was thinking about a way to explain a woodworking tip by using 3D solid modeling to easily illustrate how joinery comes together in the field. My thanks to Vectorworks for allowing an easy generation of a polygon and extrusion to a solid.

…PSA announcement:

• For the woodworking experts and carpenters, I’m sure you can explain this better and more technical, so I welcome your comments and feedback. I am not a professional carpenter.
• For the computer whizzes and modeling geniuses, you can use your skills to think about woodworking in a new way perhaps. I’m sure you understand 3D solids, how to model them and how to manipulate them. If you’re not especially handy apart from the computer, perhaps this will inspire you to put down the mouse, pick up the saw (after searching YouTube for a few safety tips) and feel confident in doing those DIY projects.
  …

Baseboards, a common but generally boring component in finish work, have an inherently challenging joinery method for those who wish to install them correctly. For us modernists, we tend to use square (S4S) trim profiles for simplicity and lack of ornament. That’s “surfaced four sides” if you didn’t look it up by now. Nonetheless, we find most people prefer a baseboard that has some type of profile to it.

Despite perfectly rough framed walls and smooth, even drywall or plaster, it is common that the inside corners will not be perfectly square. If the angle is anything but 90 degrees, mitering the inside corner like an outside corner will usually result in a poorly executed joint and a carpenter that is ready to smash something from the frustration.

What’s the trick? There is a method using power tools or a rotary tool, but that generally works better for a profile where the bottom is mostly square. In our project, only the bottom third was square (and we were lacking in some tools). Despite our love of power tools, the key to this Jedi trick is a simple hand tool – a coping saw. Nonetheless, having an orbital sander available makes it considerably easier to make a cleaner joint. Sandpaper  or a file works well if you’re patient, but who doesn’t love power tools?

When digitally modeling solids, it’s quite easy to take one solid object that overlaps another one and subtract one solid from the other. The software does the insane calculations to remove the material of the overlap, leaving a shaped solid. If only it was this easy with wood.

Until we can replicate this method with wood, here is how I’ve learned over the years to make this joint.

Step one:

Vertically cut the correct end of the base on a 45-degree angle. Insert the base vertically into the miter saw and make an open miter cut. This magically creates an edge that can be followed with the coping saw. If the wood is primed, the edge between the paint and the wood color makes it quite clear.

Step two:

Take the coping saw (FYI it cuts on the pull or back motion – look at the teeth) and slowly remove the wood material outside of the base profile. This takes practice and the first time one does this is generally a mess. When the top of the base has a convex curve, it results in a small, sharp edge that often breaks off during the process. The key is to cut the wood with a slight back bevel leaving a knife-like edge that will barely touch the adjacent piece. Removing the back material is critical to allow the face of the base to touch at the corner for a tight joint.

perhaps I gave him too small a piece of scrap to practice, but well done…

 

Step three:

Sand (or file) up to the edge smoothly without crossing the line. If you cross the profile line, you’ll leave a gap, or the joint won’t be tight.

my son is enjoying power tools

Step four:

During installation, it’s common, if not necessary to slightly tap the cut base into the receiving base to force the profile into a clean tight joint. Once that joint is established, the base can be measured and cut to length. Several of these could be cut ahead of time to speed up the process.

Tip – only make this mitered cut on one end of length of base. It’s virtually impossible to do it to both ends; no one is that good, not even with the Force.

here is one finished corner awaiting some caulk and paint

OK, at this point, you’ve probably messed it up. What went wrong? Ask a few questions.

1. Is the receiving base plumb or was it drawn in at the bottom due to an uneven wall or the tapered end of the drywall? Look for where the gap is.
2. Did you accurately follow the profile exposed on the first 45-degree cut? Don’t cross that line.
3. Did you remove all the material along the back of the base so only the surface of the cut base touches the other end?

If you’re an expert woodworker, you may find flaws in this description or you may have a more magical way with a miter saw or rotary tool. The base profile is a factor.

What is the alternate?

1. Lots of caulk and wood filler – that will show up on an architect’s punch list.
2. Square trim that can be butt joined – always my preference.
3. A reveal base – look that up (Fry Reglet) – another favorite if I can convince the owner.
4. Baseboard corner blocks – it’s a bit too fussy for my taste.
5. Hire someone else. This is only when there is no other viable solution.

Until we can manipulate material and subtract solids literally like a digital tool (CNC machine?), learn to use a coping saw. It takes discipline, it takes skill and it takes practice. There’s a mental or spiritual mindset to learning to using tools.

Every architect needs to get their hands dirty now and then. If nothing else, it helps us to understand the joinery of our designs and breeds respect for the crafts people that build them.

I got to do this with my son and explain this to him. I was truly in my happy place. Maybe, I have a second career awaiting me.

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