Sunday, December 19, 2010

Reverse-engineering a 4-drawer chest

A friend of mine brought me this challenging job: re-building the case of a 4-drawer chest, which had been destroyed during a move.  Since the drawers were intact, and complicated to build, my friend wanted to keep them, and only wanted the case rebuilt.  This is backwards: usually drawers are made to fit the case.  Nevertheless, I welcomed the challenge, the $$, and the chance to work with a new product I've been dying to try: bamboo plywood. 

I purchased 3/4" bamboo plywood from Cali Bamboo.  In spite of the hefty freight fee, it was still cheaper than buying locally.  Bamboo plywood isn't cheap, though: at just over $200/sheet, including shipping, mistakes with this material are expensive!
using the Domino mortiser
There are many advantages to bamboo plywood, however: it's renewable, the edges look good and don't need edge banding like plywood does, and its faces are good looking, too, imparting a real 21st century aesthetic to furniture. 

I decided to tackle the project by rough-cutting one sheet of 3/4" bamboo plywood into 4 24x48"sheets.  I made the cuts using a Festool TS75 plunge saw and its guide rail.  The huge 8x4' sheets are way to big for my table saw.  i was worried about the squareness of the cuts with the plunge saw.  As will most things Festool, however, I was pleased with the results of using the plunge saw & track.  I cut Domino mortises in the edges of the bottom panel, and along the bottom of the inside face of each side panel.

Then, I used the original chest's gouged drawer dividers as templates to cut the 5/8" MDF I was going to use for my dividers.  Why MDF?  Well, the original's drawers were made with MDF, and the rest of the original case Including the original dividers) was made of fiberboard laminated with melamine.  Since we were upgrading the outer case from fiberboard & melamine to Bamboo, but still working on a budget, I upgraded the fiberboard dividers to MDF, but not all the way to bamboo.  As it turns out, 5/8" MDF isn't easy to find.  If you're in Boston, try Boulter Plywood.  The guys there are really nice (if in a hurry!), and they'll deliver, usually the same day.  They charge $40 to deliver small orders, but it's well worth it.

The, using some 4-foot cabinet clamps, I assembled the bottom and side panels, and then fit each original drawer with its original runner and new divider.  Of course, the dividers were too tall, and both the top and bottom panels too wide.  But this way, I was able to account for the slight deviations in each drawer, stacking them together first, THEN cutting the case panels to final size.

the Festool TS75 plunge saw and track make laser-straight cuts
A perfect fit for the case parts is critical, since my friend specified a mitre joint along the top right and left edges of the case.  I was advised by a carpenter friend to use an old finish carpentry trick: the turnaround.  But I decided to go "honest" with my construction and cut the mitre, joining it with floating Domino tenons.

Here you can see the dry assembly.  From here, I plan to mark and then cut the case parts to proper size.  A back piece, made of MDF and sized to the inner dimensions of the case, will be mortised-into the case panels, giving the whole thing extraordinary strength against racking.

The view from the top rear - fitting assembly
Stay tuned for part II - where (hopefully) I assemble the final case, hang the drawers on their dividers, and then finish the whole thing in beautiful and durable oil urethane.  

-isaac

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