Chair jigs

You can click on any of these pictures to enlarge them.

1: This is the seat drilling jig.

There are two sides of plywood, connected by the thickest piece of timber availiable ( usually 8/4 ). The base should be as long as your seat is wide for easy centering and clamping. The plwood should be tall enough to register your drill bushing ( see fig 4.)

3: Front view of the seat jig.

After attaching the plywood to the base I set a bevel gauge for the rake angle and staple 3/4" square guides to the plywood. The spacing is taken from the template as before. I always scribe a center line around the base and use that as reference for attaching the plywood and laying out the spacing.

5: Jig clamped to seat.

Draw a center line on the seat blank and line up the centerline of the jig. Use the seat template to determine the setback from the back of the seat. In this case 5". I always write this setback number on the back of the jig.

7: Drilling

Use high drill speed and light pressure, especially as you're breaking though the bottom. One side of the drill bit will break through before the other and if you're pushing hard, it will split some off of the bottom of the seat.

8: spindle jig.

The center spindle drilling jig is the same, but the side guides are at 90 deg. The angle is the back slouch angle of the chair. The plywood base must be long enough to clamp on either side of the chair.

10: Strecher drilling

This is not the correct jig for this chair, but I don't have the right one availiable. The premise is a block that holds the drill parallel to the bottom of the seat, at the right height. sometimes I have to attach a large plywood base to this jig, so that it can be clamped to the chair. Most of the jig is sometimes hanging in the air and you need some way to stabilize it. The block must be short enough to fit inbetween the legs.

You need a drill with a top or side that is parallel to the bit to be able to do this ( or make something to fit the drill)

2: This is the side view of the seat jig.

The base is cut with the front leg rake on one side and the rear leg rake on the other. I figure the width by using my half seat template and subtracting for the thickness of the plywood and the offset of the drill bushing ( 1/2")

4. The drill extension and bushing.

I made this wooden bushing to fit my extension. It is 1" dia. on the outside as the biggest bit I use is 7/8". This allows me to standardize all of my jigs with 1/2" offset and I can use any size drill bit with any jig. This cuts down on confusion and opens up new possibilities.

6: Drilling the hole.

Hold the bushing tight into the corner of the guides and place the point on the seat. I rotate the bit to see if its in the right place. With a 7/8" bit the edge of the bit should be 1/16" from both the guide and the plywood. If it's not move the center a little in the right direction. This method works, as my stretchers consistently come out the same length.

9: Drilling

The center is marked and the jig set 1/2" in front of the mark. This is the offset for the bushing. A centerline is marked all the way around the jig and lined up with the centerline on the seat. It's important that the center spindle is perpendicular to the seat.

The same type of jig at a different angle is used to drill and ream bowback bow mortises and the end spindles of fanback chairs.

11: Aiming the drill

I put a cross on the back end of the drill to aim at the mark or hole that I am drilling away from. To find the mark I chuck a piece of rod in the drill and the hold the rod ( with drill attached) in a chuck in my lathe. Bring up the tailstock to mark the drilling center on the back of the drill.

Brian Millspaw

skull