Wednesday, September 28, 2011

Prairie Chair -- Frame and Panel Construction

In many ways, making prairie-style furniture is like building a series of cabinet doors and sticking legs on them.  It requires only the foundational skill of frame and panel construction.  And because quarter-sawn white oak is fairly tough, some robust stationary equipment.  I wouldn't want to contemplate building this as a hand tool project.

Setting the quadrilineal legs aside, I start by building the frames, and then building the panels to fit.  I started with plans from Robert Lang, but have modified them over several iterations and worked out the bugs.  All stock is 13/16" thick, and all grooves start at 1/4" wide by 1/2" deep.  On my notes, I draw boxes around dimensions that are gross (including tenons) and then write tenon dimensions next to these numbers.  To avoid confusion, I write the distance between tenons (the net dimension) in another place.  The frames come together quickly and I dry fit them right from the machines.  I've become increasingly fussy about keeping every machine in perfect alignment (and trust me this is not in my nature) and it saves so much time and frustration.

After selecting the second-best figure (I saved the best for the arms), I resaw the panels right from stock that has been made square and true from 4/4 stock.  I want to net out something above 1/4" for each panel.  You may well need all that extra thickness as qswo will warp a great deal after it is resawn.  I've found that working with stock to net two doors at a time (30" or so works best for me.)  Resaw, joiner, planer and set aside.  Joint the edges and bookmatch.

Once the glue has dried, I bring out the beast.

I bartered this from another woodworker who thought he'd use it a lot, but didn't.  All it cost me was several days of hair-raising, high-wire act ceiling installation.  Moving very slowly, with 80 grit paper, I achieve a "uniform scratch pattern."  It is amazing how quickly the finish sanding goes when you use this to true up the surface, don't skip grits, and sand two panels at a time.

Flipping to the back side, I use a 3/4" straight cutting bit to thickness the edges of the panels to 1/4" to fit in the frames.  In they go, and it's time for a quick dry-fit.  As you can see, I leave a bit of room for movement within the grooves.

 I generally stain panels before construction to avoid having white wood expose itself in the middle of winter, and as it is so humid right now, that is a necessity.

The arms on the prairie chair are very simple, but require two absolutely accurate 90 degree angles or the effect will be ruined.  Starting with straight and true stock, I put them in my tablesaw miter jig.  There's nothing too exotic here, just micro-adjustments to dial in a fit.  One key is to have a support on the right of the blade to catch the piece that falls off when the cut is complete.  Securing the workpiece to the jig with a clamp, and starting with a sharp-ish blade, also helps.  Once in place, you just need (as Julia Child says as she's about to whack a chicken into two pieces with an enormous meat cleaver) the "courage of your convictions."

My handy angle block tells me everything is cool -- but I knew this already as I had made a test cut.  Someday I will have a Lie-Nielsen No. 51 and I'll be able to fine tune this with a clearer conscience.  But I don't see that happening soon.

Now, I pretty much have all the pieces ready, and it should look like a chair within the next few days.  Cheers!

Friday, September 23, 2011

More Quadrilinear Boffinry

Well, after my long summer hiatus, the last thing I wanted to do was re-emerge with a Don Quixote-esque post about chasing the perfect quadrilinear leg post, but here goes.  As you probably know, the quadrilinear leg post is an identifying feature of high-quality arts-and-crafts furniture.  By careful construction, it allows you to create a post (in this case 2.5" by 2.5") that displays quartersawn grain on all four faces.

Every iteration of the Stickley factory has used this technique, and even low-end manufacturers tried to mimic the effect with a faux finish.  If this type of discussion floats your boat, I encourage you to check out the excellent book, Arts & Crafts Furniture: From Classic to Contemporary by Kevin Rodel and Jonathan Binzen.  It is equally appropriate in the workshop or on the coffee table.

In the past, I've used the standard whacking big locking mitre bit in the router table with less than satisfactory results.  Yes, I have a big 3 1/4 hp router and a nice Jess-Em table, but the whole process still scares the bejesuz out of me -- one slip and you've ruined a nice bit of timber.  Here's one I made earlier:

It was so good that I cut it up and used it to support a shelf.

I've also just mitered the four long edges, glued the faces, and using strapping tape, rolled it up in a bundle.  The results are nearly as good as the lock mitre bit, and slightly less nerve-wracking.  You do, however, often end up with one less-than-perfect joint.  I can hide it in construction, but I'm not happy about it.

So, with the price of  4/4 quartersawn white oak at $7.50 per bf around my neck of the woods, I decided to give modified veneering a shot.  Veneering has many things going for it.  It cuts your timber costs in half, and allows you to select some particularly tasty figure for the post you are making.  The drawback, of course, is that making your own veneer requires some (expensive) machines and can be tedious.

I started by making two 60" cores of 3/4" plywood.  As I wanted to net out around 2.5". I cut the width to about 2 5/16".  this allows me about 3/32" for the veneer on each side.  I stacked three of these core pieces of approx. 3/4" plywood to a net something less than this (plywood being less than its stated dimension.)  I would compensate for this with one slightly thicker veneer on that side.

I selected some very nice pieces of QSWO that were 2.75" by 62" -- from different boards but with similar figure.  This was facilitated by the fact that most of my stock was around 5" wide, and I needed to the leftover 2" pieces to make corbels.  I cut 1/4" veneers on the bandsaw with some great blades I recently purchased from Woodcraft Bands.  He puts together blades that resaw as well as that big name brand, but at a significant discount.  It is important that between each slice you pass the stock across the joiner to have one flat face.  When complete, you will have eight slices.

Now, I know that 1/4" stock isn't really veneer, and that it is at risk of seasonal movement.  At the heart of this method is reducing the thickness of each piece while it is attached to the core, requiring you to always have a dead flat surface to reference in the planer -- so sequencing is important.

1.  Glue up one veneer (flat side against the core) to the core with the edges of the veneer standing proud.  I do two legs at once and clamp.

2.  Once cured, run this through the planer (veneer side up) to get the veneer to about 3/16". Repeat this process on the opposite side.

3.  Now trim the overlapping veneer edges flush on the router table with a spiral flush trimming bit.

4.  Now repeat the glue up, in a similar fashion, on the remaining faces, cure and trim the edges on the table.

5. Finally, and with a great deal of attention, run the completed posts through the planer to achieve uniform thickness.

There is no doubt that this is a fiddley process, and you can argue that the money you save on stock you spend on shop time -- but I'm really happy with the results.  In addition, because there a number of steps that require cure time, you can fit it between other tasks.  The other issue is deciding how thin you dare go with the veneer, and how much you reckon QSWO is going to move.  I'm comfortable with 3/32" -- chunky enough to withstand wear, but not thick enough to overpower the glue with movement.  So, let me know what you think.  Thanks!

Next, I'll construct the Prairie Chair.