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Chisel Cabinet - Day 06
Entered: 2010-01-20
Edited: 2010-01-20
Type: woodworking

Day six of the build is all about the mortise and tenon joint. The mortise is just a rectangular hole cut straight down into the surface of the wood with a chisel to a pre-determined depth. A tenon is simply a matching tab cut into the end of a board that fits snugly into the mortise. When done properly this is one of the strongest joints available for a woodworker to use. There are many variations on how this joint is made that affect it's strength, assembly and appearance. For these doors I'm using the blind, draw-bored variety. Blind just means that the mortise doesn't go all the way through the board it's cut in and draw boring is a technique for pulling the joint together with a dowel driven through offset holes in the mortise walls and the tenon. I like the way this type of joint looks and the assembly is simplified because I won't need clamps - it's also very, very strong and can survive centuries of use without failing.


It's been several months since I've had to cut any mortise and tenon joints for a flat frame like this so I'm doing a practice one first to get warmed up, and it's my practice run that's documented here.

The first and most important step when making M&T joints is to carefully set your marking gauge and mark out your layout lines. The mortise gauge has two pins in the end, one of which is movable with a little thumbscrew on the other end. It's most accurate, when working by hand, to just set your gauge to the exact width of the chisel you'll use to cut the mortise. When I start chopping my chisel will fit exactly inside the lines I've marked, which will make it easier to keep straight.





I mark out my tenon using the same settings on the gauge, which gaurantees that it will be the exact width the hole my chisel cuts. Or at least that it will be marked the exact size of the hole my chisel makes ;-)



When cutting my mortises I like to clamp the board into a clamp that is in turn clamped to my bench, preferably over a leg.



Then I chop it out.



There are MANY ways to cut a mortise by hand - I prefer to start in the middle and cut a deep 'V' until I'm close to the ends, then I start making vertical cuts until I get to the ends. Mortising involves hitting the chisel with a mallet to cut deep into the wood then levering out the waste from the hole, all the while keeping everything square and aligned to your marks. It's both easier and harder than it sounds. With enough practice with hand tools you start to get a good feel for when a tool is being held square to a surface and is running true, it's just that while practicing you'll cut a lot of twisted, out of square mortises.



I'm done when I hit my target depth and the walls of the mortise and clean and square.

Once the mortise is ready it's time to cut the tenon. To cut the tenon I put the in my vise at an angle so I cut straight down from the corner, then flip the board around and cut down from the opposite corner and the set upright in the vise for a final straight cut.



After both sides have been cut out I need to cut the waste off. To do this cleanly and accurately I use a wide chisel to cut a little trough along my marked line for the saw blade to rest in. This helps get a clean and straight start on the cut.



Then I mark the width directly off the mortise and cut it to fit exactly.



Finally time for a test fit. Looks good so far, looks square too.



Uh oh. Got some major fail here. My rail is leaning badly to the right and I made the tenon too thick and it's split the stile. That's why this was a warm-up piece. Goes without saying that I did another practice run, which came out spot on, before mauling the actual door frame. On my second practice run I did a lot more tweaking of the joint for a perfect fit. I won't bother to document any of that extra detail work here, mainly because my Woodnet friend Derek Cohen already has a brilliant tutorial on his website that I can't improve on by replicating it here.

The next several days of work will be exactly like this and won't warrant their own posts. Next update will show the finished frame followed by some panel raising.

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