Sunday, November 27, 2011

The Hammer Beam Low Table . . . Creating Corbels and Making Sliding Dovetails

With the greater part of the base complete, it is time to tackle the decorative corbels that adorn each foot of the table.  I began with the idea that a stacked and constructed piece, incorporating a large tenon, would add visual flair and lock the curved beams in place.

I construct each corbel with five small pieces of stock -- a tenon, an upper internal piece, a lower internal piece, and two external cheeks.

The tenon and the internal pieces ready for glue up.
As the individual components are all small, I use "rub joints" and line up the pieces by eye. I start with a sub assembly of the internal pieces and add the external cheeks once these are dry.


Using my initial drawing as a guide, I place an arm on my bandsaw's circle cutting jig and set the it for an 8 3/8" radius cut.  Aligning the drawn piece against the curve, I'm able to hot-glue two stops on the jig to transfer this curve on the glued blocks.  A bit of carpet tape holds the block in place and they pop out of the jig nearly complete.  A quick chamfer on the front edge and a bit of sanding results in a finished corbel.

The end grain was sanded quite easily with the pneumatic sanding attachment on the drill press, and as I'd already checked the fit of the tenon in the base unit, everything came together with just a bit of work with the shoulder plane.

I'm joining the two base assemblies together with a stretcher that attaches with sliding dovetails.  I always enjoy making sliding dovetails.  There is a great deal of instant gratification as the pieces come together in a perfectly fitting joint.  It also helps that I have a method, and a pair of bits, that make it very easy.

The stretcher is 3" wide and will attach dead center at the top of each base assembly.  Because I want this to be a stopped mortise, I will only cut the groove about 2 1/2".  I start by finding center on the mortise stock and begin to make a 3/8" groove on the router table.  I bring the depth to 1/2" in a number of passes.  Experience has taught that if I create this groove, and follow it with a single pass with my Lee Valley 5/8" x 14 degree dovetail bit (#16J1755), set to a depth of 1/2", I get a perfect sliding dovetail mortise without stressing the bit with too much stock removal.  The only challenge with this technique on the router table is that you must make the bit change in a way that allows you to keep the fence in the same place.

The advantage to the router table is that once you have made the pass with the dovetail bit in the mortise, you have automatically set the right height for the bit to cut the tenon.  All adjustments to the width of the tenon will be made with the fence. I like to start by marking a deep mark in the tenon stock with a gauge to help eliminate tear-out.

I adjust the fence, using test stock of the same thickness and with passes on each side, until I have a snug fit.  Patience is key here as you dial this in -- one overly-ambitious cut and you will need to start over.  Using a jig, or your own steady hand, cut the tenons to size.

As these are stopped joints, you will need to remove some stock from the tenon to complete the joint.  I start by sliding the tenon into the mortise until it stops.  I set my gauge to this depth, mark the tenon on the bottom of the stretcher, and remove with excess with a hand saw.

 
Although this joint will never be seen, I do get some weird kind of satisfaction as it comes together without a hitch.


In order not to bore you (too much!) I did gloss over some of the specifics of how I went about these parts of the project -- but I'd be happy to go into more detail if you have any questions.  I'm also open to being shouted down if you see some glaring error, or know of a better technique.

Next up -- the breadboard top.  Cheers!

6 comments:

  1. Looks great, can't wait for the top!

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  2. Thanks. The decision between QSWO for the main part of the top and flat sawn for the ends (or vice versa) was made for me as I a) have more QSWO than flat-sawn and b) it is raining and I don't feel like going out. High level design decisions!

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  3. Wow, that looks really good. Thanks for the post on the incorporating architectural details into the design. It really shows through.

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  4. This comment has been removed by a blog administrator.

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  5. Thanks, James. Given the way I've re-oriented the piece, I should call it the Upside-Down hammer Beam Table!

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  6. great article Yes, thank you already want to share a great article

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