How to Insert a Top Bearing Flush Trim

Unplug the router, and locate the height adjustment lock nut. They are typically located at the top of the router's base on the side of its barrel. Turn the nut counterclockwise to release it. Then turn the router's base counterclockwise to twist it down and off the bottom of its barrel.

Stand the router on its top, and fit two wrenches to the nuts on the routers collet, or bit collar. They are located in the center of the bottom of the router. Turn the outside nut counterclockwise and the inside nut clockwise, to loosen and open the collet. Remove any installed bits from the router by pulling out.

Fit the stem of the flush trim bit into the router collet, until the bearing is 1/2 inch from the collet nut. Tighten the two nuts by turning them opposite the direction as to loosen the collet; turn the outside nut clockwise and the inside nut counterclockwise.

Position the router base on the bottom of the router barrel. Twist the base clockwise, until the height of the bit is set correctly. The bearing at the top of the bit should be far enough from the bottom of the router base to ride smoothly along the edge of the template piece. Tighten the router base height adjustment lock nut by turning it clockwise, locking it in place.

Stack the template piece on top of the material to be cut. Clamp them together with C clamps. Set the router on the top of the template piece, with the bit extending down. Start the router, and run it right to left along the edge of the template piece -- with the bearing riding along the template piece edge -- to make your cut.