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Cutting pyramids on top of tapered chair backs – Kevin Rodel’s side chair

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Blog entry by DHS posted 10-15-2019 04:52 AM 735 reads 2 times favorited 2 comments Add to Favorites Watch

I recently built six craftsman-style dining chairs following instructions in Kevin Rodel’s article in the March/April 2007 issue of Fine Woodworking (Vol. 190). However, one seemingly simple procedure (that was not well described in the article) had me flummoxed. The article stated instructed the reader to, “Cut the shallow pyramid heads on both the front and rear legs.”

Yes, I needed to cut pyramids on top of the front and back legs. The front legs were no problem. The legs were square. I just marked the location of the pyramid base, angled the blade of the chop saw (22 degrees) and cut the first facet that intersected the pyramid baseline. With a stop block in place, I rotated the work piece and cut the other three facets. Simple. But, each side of the back legs had a different taper. So if I were to use the same procedure on the back legs, each time I rotated the leg, it would have a different orientation to the chop saw blade. The four facets of the pyramid would not meet. But, how would I compensate for the different tapers on each side of the back legs?

I found a couple of weblogs that described the procedure. But, I was not satisfied with the descriptions. The method involved setting the miter gauge and table saw blade to specific angles and it occurred to me that if my chair legs were not exactly the same shape as the blogger’s chair legs, the quoted angles would not be meaningful. And, I thought there must be a more general solution to the problem, using the leg itself to adjust the blade angles.

I pondered this for about two weeks. Then, one night I couldn’t sleep and I began puzzling over this problem. I imagined the Washington Monument. Like the back legs of the chair, it is tapered on four sides and has a pyramid on top. Then, I imagined tipping the monument over onto one of its sides on level ground. We’ll call the level ground a reference surface. Since the bottom side of the tipped-over monument was now parallel to the reference surface, the monument was now tapered on just three sides. I then imagined a wall, perpendicular to the level ground. We’ll call this a second reference surface. If I were to push the monument against that wall, it would then be tapered on just two sides. Maybe this is a lesson that most woodworkers already know, but it was new to me. A work piece tapered on four sides can be “converted” into a work piece tapered on two sides by simply defining two adjacent reference surfaces.

Back to the chair… I defined the inside and the back surfaces as my reference surfaces. I realized I could then mark the base of the pyramid. Setting my T square fence against the edge joining the two reference surfaces, I marked the base of the pyramid on both reference surfaces. Then, again keeping the fence against the reference surfaces, I extended the base across the tapered surfaces. The base was now marked. It was time to cut the pyramid. Back to the chop saw…

For the first set of cuts, I placed one reference surface against the base of the chop saw and the other reference surface against the fence. With the blade perpendicular to the chop saw base, the blade had to be parallel to the pyramid base (because I marked it perpendicular to the reference surfaces). I cut the first two facets of the pyramid by rotating the blade to the left 22 degrees and making one cut then rotating the bade to the right to 22 degrees and making a second cut. These cuts landed precisely along the pyramid baseline.

To make the second set of cuts, I rotated the rear leg 90 degrees. Now, one reference surface was against the fence and the other reference surface was on top. The blade, therefore, was no longer parallel to the base of my pyramid. If I were to cut the last two facets, I would end up with a really ugly pyramid. But, there’s a trick, using the work piece itself to adjust the blade angle. I simply placed a square on top of the chair leg and slid it over to the chop saw blade. I rotated the chop saw blade (to the left of vertical) until it was flush with the square. Now, the blade was once again parallel to the base of the pyramid.

I rotated the blade left and made a cut, and rotated it to the right and made the cut… A perfect pyramid!

Now, for those of you who have made it to the very end of this blog and are thinking, “I don’t have any plans to cut pyramids on top of tapered work pieces. Why did I just spend 10 minutes reading a detailed account about how to do it?” There is a more general take-home message: Always define adjacent reference surfaces! Even if your work pieces are not tapered, keeping track of reference surfaces will improve the precision of workpiece dimensioning and joinery. And, if you do something weird such as tapering or curving a surface, defining reference surfaces might be imperative for successfully executing your project.

-- Dave S., Bellingham, WA



2 comments so far

View pintodeluxe's profile

pintodeluxe

5996 posts in 3347 days


#1 posted 10-15-2019 06:31 PM

You sound like a thoughtful woodworker, which I can relate to.

This procedure looks so simple, but once your try it, you suddenly realize its more involved.
I run into this issue on dining chairs and Morris chairs.
One solution I’ve found that really works great is to use an oscillating belt sander to create the chamfer. Use a miter gauge to support the workpiece. Angling the miter gauge, combined with occasionally setting the table at an angle, you can create any angle you need.

You can sneak up on the angle with course sandpaper, then switch to fine paper near the end.

I covered the topic in a blog post a few years back… https://www.lumberjocks.com/pintodeluxe/blog/40222

Thanks for sharing your technique, and your project.

-- Willie, Washington "If You Choose Not To Decide, You Still Have Made a Choice" - Rush

View DHS's profile

DHS

137 posts in 3758 days


#2 posted 10-16-2019 03:24 AM

Good alternative to the chop saw. My question is how do you set the angle of the table? If you have a tapered workpiece, you would still need to define two adjacent reference surfaces and start with those surfaces against the table and the miter gauge. Then, I suspect you could use the same technique I used to set the angle of the table after you rotate the workpiece (a square on top of the workpiece butted against the belt sander). But, I think it would be a challenge to butt a square against the belt sander.

-- Dave S., Bellingham, WA

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