Thread: how to make large perfect rectangle rebate in hard wood?

Make up a perfectly rectangular frame to be used as a routing guide. Use trig to ensure the squareness, or a good square. It will need to be wider than the area you wish to rebate out by the width of the router guide plus some.

You will also need to chisel out the corners square once you are done.

Agree with Wongdai with regards the template - however, the granite bits you have need to match the rectangle - often the "manufactured" rectangle etc is not a perfect rectangle but will be close.

Are the corners of the granite rounded - are all 4 the same?

I would place the boards on the top where required, use a laminex sample piece vertically against the edge to ensure you have some relief for expansion of the timber and to ensure your line is cleanly transferred to the timber. [available free from most hardware stores - approx 0.9 to 1mm in thickness]. This way you match what you have rather than you have the perfect rectangle and your granite isn't.

The top being raw timber and not even is a bit of a concern but can be overcome by flat, thin bits under the router to bridge the unevenness.

Regards,
Bob

How I would do it:

If the chopping board is not perfectly rectangular, or has a better surface on one side, mark the bottom "This side down."

Measure the distance from your router bit to the outside of a router bushing. This is the offset requirement.

Place the chopping board in position. Add shims of thickness equal to the measured distance above, plus clearance allowance, on all four sides of the board. Place lathing strips along the shims in pinwheel fashion, so that lengths are not critical and corners are reasonable tight. Attach the lathing strips with hot-melt glue. Rout the rebates, using the lathing strips to guide the bushing. Use a corner chisel to fit the corners.

If the interior is to be solid, rout that portion first. In any event, it will help to have a through-hole to facilitate removal of the chopping board.

After removing the hot-melt glue, re-finish as needed.

Cheers,
Joe