The Family-strength Highchair
(Page 2 of 3)
March/April 1986
By the Mother Earth News staff
It's probably easiest to cut the mortise on a router table by drilling a lead hole for the bit. Unless you have a very powerful router, though, don't expect to remove all the material in one cut. As an alternative, you could do the job on the table saw by lowering the stock onto a dado and then cleaning out the ends with a chisel. This is a fairly hairy operation that shouldn't be attempted without appropriate jigs and feather boards. In the end, it might be quicker to cut the mortises by hand with a chisel than to set up for either the router or the table saw.
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SIDE FRAMES
Glue the side frames together first, clamping each joint to ensure a good bond. (There's plenty of surface area so screws aren't really necessary.) Once the glue has had time to set, round the front and back of the arms with a coping, saber, or band saw.
Next, round over all the edges to protect small hands from splinters. The quickest method is to use a router, but unless you have an extraordinarily steady hand, you'll find it to be just about impossible to avoid burning hardwood with a standard rounding-over bit. Therefore, a 3/8" rounding-over (or cornerbead) carbide bit with a pilot bearing is highly recommended for this job.
FINAL ASSEMBLY
The last component you need for assembly is the seat back. Use the bottom dimension provided in the drawing, with your tablesaw miter gauge set at 83°, to cut out a polygon. Then, in the top of the piece, saw an arc that pleases your eye. Sand out the major irregularities your saw left in the curve, and round over the front and back, stopping short of the sides by about 1/4". It's safer to sand this last bit of curve to blend well with the flat, butted sides.
Set the seat and cross braces in place temporarily, and locate the position of the chair's back. Then clamp everything temporarily while you drill and countersink the screw holes for the butted back, the mortised seat, and the cross braces. Pop the clamps back off, apply glue, reassemble, reclamp, set the screws, and let the assembly sit overnight.
For the sake of appearance and to avoid traps for mini-compost piles of spilled food, all of the screw holes should be plugged. Be sure you don't countersink any deeper than about 1/8" on the cross braces or you'll come through the joint. If you use Phillips-head No. 8 X 1-1/4" screws, you should be able to apply enough torque to seat them firmly into the bottom of the screw holes. Nonetheless, commercial screw-hole plugs will have to be trimmed flush with a sharp chisel.
