Monday, November 26, 2012

Corbels, Arc, Mortises & First Dry Fit

Using my Sketchup model as a reference I drew the shape of the corbels onto the prepared stock, and cut it out roughly on the bandsaw.  Then with sandpaper and a card scraper I smoothed them out to their final shape.

I forgot to take a photo of the setup for drawing the arc, but basically I bowed a piece of plywood to the correct vertical distance at the center point of the arc and traced the curve with a pencil.  Cut it out roughly on the bandsaw, and smoothed it out with sandpaper.

The mortises will be done with my benchtop mortiser, but before I drive out to my brother's shop I need to spend some time marking out where the mortises will be.

Step 1: Mark the height of the mortise using the actual tenon as a guide.
Step 2: Use a marking gauge set to the distance of the cheek of the tenon from the face of the tenoned part to mark where the face-side edge of the mortise will be.  This will ensure that the faces of the parts will be flush to one another when you assemble them.

Step 3: Hold the tenon in place and draw the opposite edge.  It's always better to use the actual part for this measurement.  Introducing a ruler at this point is an unnecessary step that can introduce errors.  If the goal is to make a square hole the exact size of the tenon, the use the tenon as your frame of reference.
Step 4: Hold the tenon in place over the mortise-part like so and indicate the depth you'll need the mortise to be.  This mark will come in handy when setting the mortiser depth stop.
Extra Step: If you screwed up one of the tenons by cutting on the wrong side of the line, like I did, and it's a little smaller than the other one, make sure you mark it clearly and keep track of it the entire time.  It's not a mistake if you hide it inside a perfectly fitting mortise.  :)
Step 5: I didn't bring my camera to my brother's shop, but drilling the mortises is pretty straight forward.  It's a square chisel with a drill bit inside of it.  It drills square holes.  For the through-mortises I drilled from both sides to prevent grain from spelching out and ruining the look.
(not bad)
(perfect, my best fitting through-mortise & tenon yet)

I used my brother's router table with a straight bit to make the double-stopped rabbets on the stiles.  I'll chisel out the corners by hand.
And here's the final dry fit.  The tenon shoulders need a little tweaking to remove the gaps and bring everything in nice and tight, and I'll probably relieve some of the tenon cheeks so the fit is a little easier so I don't run into trouble during glue-up.

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