Layout the location for the square hole.
Using a small square, center the punch on the layout.
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Now lightly tap it in place to registers its position. Often the punch will stay put when you remove your hand - if not it is easy to relocate.
Now, using a bit that is 3/64" under the size of the square hole (3/8" square hole - use 21/64" bit), drill out the center. Use an ordinary twist bit for this and not a brad point. The leading sharp corners of the brad bit will catch on the inside of the chisel and damage themselves.
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To finish off - strike the punch with the hammer to its final depth. Before removing the punch use the drill once again to remove most of the wood chips.
Remove the punch for a perfectly square crisp hole!
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The Hollow Square Punches will be available from Lee Valley Tools very soon.
Use the product code 50K5920.
For more on the Hollow Square Punches see my previous blog.