Back Splats

I experienced an interesting situation while trying to achieve symmetry in the back splats. It may seem counterintuitive, but in order for the back splats to look like mirror images of each other, they can't be book matched. Book matching, the traditional way of obtaining a mirror image, is good for veneer work and other flat applications, however, with sculpted work it simply doesn't render a mirrored appearance.

WARNING: If you thought my previous posts were a bit technical, fasten your safety belts. This one's a doozy.

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If technical stuff isn't your thing, I hope you'll stick around and enjoy the pictures; they tell most of the story. I'll try to get back to my usual writing in future posts, but I just can't resist sharing some of the complexities and nuances I discovered in this phase of the chair making journey. I love this stuff!!!

For these back splats, I've selected two parts from the same plank where they were positioned end-to-end. I'll orient the ends that were adjacent in the plank toward the bottom end of the splats. The next step is to straighten the cuts so that the rough rectangular blocks have the grain lines running straight through them. I'm paying very close attention to the heartwood and sapwood color variations, as well as the angle of the endgrain. All of these will help to secure the desired symmetry and ensure that the grain lines are pleasing to the eye.

With the parts rough cut, I then determine the angle for cutting the shoulders on the table saw. And follow that by cutting the tenon cheeks on the bandsaw.

Below you can see the lower tenons fitted to the lumbar rail.

I'm afraid the upper tenons won't be quite so easy. For those, I need to carefully determine the exact tenon location on the ends of the splats as well as the two angles needed for cutting the shoulders. To do that, I put temporary floating tenons into the mortises of the crest rail, spacers on the tops of the back legs using extra long dowels, and then assemble the crest rail over the tops of the splats. Before actually cutting the end of the splat to length, I estimated the needed angles with a couple of story sticks placed between the lumbar rail and the crest rail, and used these settings on the table saw for the first preliminary cuts. I started with 3/4" spacers over the legs and moved to 5/8" spacers as I dialed-in the exact angles for the cuts and the length of the splat, tweaking the blade and miter gauge angles until I had it just right.

With the compound angles cut at the top ends of the splats, I then traced the ends of the floating tenons onto the back splats and set my marking gauge to the thickness of the spacer minus the projection of the temporary floating tenon. This gave me the length needed for the tenons (I should note that the floating tenon length is the same as the spacer thickness).

I then scribed this measurement around the ends of the splats with the marking gauge and cut the compound angled shoulders on the table saw, carefully using my eye to align the cut with the scribe line.

Fitting of the tenons into the crest rail leaves me with some mighty heavy duty back splats.

This was remedied by tracing the side and front views of the back splat and cutting them out on the bandsaw.

Now it's starting to look like something. From it's thick beginnings, the back splat is much closer to its final 8mm thickness. After giving the four sides of each splat some shaping with the block plane and spokeshave, I proceed to layout a series of curves to use as guides in the final tapering and shaping.

The next shaping stage is to use the spokeshave to chamfer the edges using the curves I just drew.

And then, soften all the edges, giving the back splats a more graceful wing-like shape.

Finally, I can see the chair-back coming together. You'll notice that the crest rail is still almost 2mm above the tops of the back legs. This gap will need to be closed by trimming down the shoulders of the back splats, one shaving at a time.

I begin this process by fine tuning the fit of the lower joints into the lumbar rail. Here I'm using a card scraper to adjust the fit.

The following close-up view shows how I used tape and a pen to mark where the shoulder of the upper joint is contacting the crest rail.

By shaving off these areas with a chisel, I can dial-in the fit.

This has been an interesting, educational and intense week, ending with a triumphant glue-up that couldn't have gone more smoothly.

But this chair won't be complete without arms, will it? That, next time.

Hej då!

Craig 

Craig Johnson is a fiscal year 2012 recipient of an Artist Initiative grant from the Minnesota State Arts Board. This activity is made possible in part by a grant from the Minnesota State Arts Board, through an appropriation by the Minnesota State Legislature and by a grant from the National Endowment for the Arts.

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