Making a Schwarz "Short Back" Chair: Part 6

Time to get beck to the legs and undercarriage.  After making and reaming a couple test holes in the waste area of the seat, I bored the holes for the legs.  Both front and back legs had a 23 degree resultant angle, so I made a guide from a piece of scrap.

Guide block set on the sightline, guiding the auger bit angle

Before reaming the hole, I mark the far end in pencil to gauge progress

Reaming the hole with homemade reamer

Checking progress along sightline with a test stick - could go a tad to the right

And checking the resultant - bang on!

Then I used a homemade tapered tenon cutter to get the legs fitted into their tapered mortises.

Tapering the tenon of the first leg

Apparently I stopped taking pictures for a while, but the rest of the legs went just fine.  Next up was making the two front-to-back rails and the side-to-side stretcher.  For these I glued up some poplar to get 1 1/8" blanks.  After squaring up, I marked for planing down to about 3/4" at the ends.

Right: marked
Middle: tapered on two sides
Left: tapered on four sides

End view of above

Planing setup for getting to octagonal, then 16-sided

Top: octagonal
Middle: 16-sided
Bottom: tapered round

The parts scraped and sanded

To bore the holes in the legs, I used Curtis Buchanan's rubber band method to find the hole locations and angles.  He stretches a rubber band around the front and back leg, at the level that you want the rails and stretcher to be (for me, that was 11" from the seat bottom).  Not only will this rubber band give you the sightline for the hole, but also you can mark the hole location on the leg so it's centered (side to side) on the leg, relative to a line drawn from the other leg's hole.  Not sure if that made sense, but essentially you're trying to get the hole where there's the most leg meat.  As a bonus, when boring these holes, I finally got to use the auger bit extension that I recently got.

There's a sightline on the seat and I line up the bit and extension with it.
For the up-down alignment, I have a piece of tape on the combo square marking where
the center of the auger bit extension should be.

Here I'm making a straight 5/8" tenon on one of the rails

After both rails were fitted, I bored for the stretcher with the rails in place.

And the undercarriage is complete, just waiting for a later glue-up

A couple of details were not covered in pics.  I made the rails and stretcher about 3/32" longer than the measurement from mortise bottom to mortise bottom.  Adding a little extra to the rails and stretcher gives the undercarriage more rigidity because it puts the chair in tension when it's all together.  The lengths were obtained using two 1/2" diameter sticks, one in each 5/8" diameter mortise and each longer than half the total span, and marking on one stick where the other stick ends.  Then you can lay the sticks on the bench, lining up that mark, and measure the overall distance.  

Next time I'll get into shaping the seat and a partial glue-up.  I'm saving the comb for last - that was a whole story in itself!