Specialized Router Bits: Instile and Rail System Cuts Strong Plywood Panelling Joints

Amana Tool Instile and Rail System

Amana Tool’s Instile and Rail System aids in cutting simple and strong grooves for setting up plywood panels in doors.

Flat-panel doors are practical and attractive. And making the panels from plywood is economical and labor-saving. No need to plane down stock, glue up narrow boards, then rip and crosscut individual door panels, and finally back-cut their edges. You can cut the panels for a dozen doors from a sheet of plywood in minutes. In addition, because plywood is stable, you can glue it into the frame to reinforce the door.

But the panel grooves cut by conventional cope-and-stick cutters have a definite shortcoming.

Conventional bits cut a looser fitting, less useful v-groove, while the instile bits make a closer fit, more snuggly seated groove for the paneling.

Conventional bits cut a looser fitting, less useful v-groove, while the instile bits make a closer fit, more snuggly seated groove for the paneling.

They’re 1/4″-wide. That’s too wide for conventional 1/4″ plywood, which is on the order of 7/32″ thick, and too narrow for 1/2″ plywood, which is thinner than its nominal thickness, too.

Plywood door panel fit into edging

Once all sides have been cut and finished, you will have a complete door with panelling fit tightly and securely in the V-grooves cut by the instile and rail bits.

Several years ago, the tooling engineers at Amana came up with cope-and-stick bits incorporating adjustable slotters for the panel groove. The two-piece slotter can be shimmed to expand it from 3/16″ to 9/32″ for thin ply. For thicker plywood, you add a third element to the slotter. Using the shims, you can expand its basic 7/16″ cut to 17/32″ for 1/2″ plywood.

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