The design presented here converts a jointer to a true thickness planer, and it takes just a couple of minutes to make the conversion. On a regular thickness planer, the work is fed between the cutterhead and a flat bed. My method’s principle, if you imagine a regular planer turned upside down, is the same: the workpiece is raised by wooden springs and pressed against a rigid overhead reference plane above the cutterhead.

My reference plane is laminated from two pieces of 3/4-in., 9-ply birch plywood. It is held above the cutterhead by an assembly of aluminum spacers, threaded rods tapped into the feed table, and wing nuts. Another necessary component is a flat leaf spring, which presses the workpiece against the reference plane until it begins to ride the outfeed table. I made the spring from two 2-1/2-in. wide, 1/8-in. thick strips of oak by steambending the last 4 in. of the strips. A simple cleat that hooks onto the end of the jointer table holds the spring in place.

The dimensions of the reference plane are not critical an 8-in. square is about right for a 6-in. jointer. Wax the underside of the plane to reduce friction. I made the spacer strips by epoxying layers of 1/8-in. thick aluminum strips together to form pairs of 3/4-in., 1/2-in., 1/4-in. and 1/8-in. spacers. The spacers are notched so they can slip onto the threaded rods with the reference plane in place.

To use, joint one face of all the pieces you are going to plane. Select spacers equal to the thickest piece plus another 1/4 in. for the spring. Bolt the assembly in place, position the spring, and back the infeed table down until the thickest piece starts to cut. Plane all the pieces at this setting before lowering the infeed table for the next cut. Continue until the final thickness is reached.

J.E. Keister, Cincinnati, Ohio

Fine Woodworking Magazine, April 1985 No. 51

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