Originally Posted by William Hamilton
I've done my share of butterfly keys already, and I've found the key (very punny) is cutting the keys with a very small inward angle on the sides and ends. I usually cut my keys on the bandsaw. There you can pitch your table 1 degree or 1/2 degree and make your cuts. Just make sure as you turn your piece while cutting it, ie. that your angle is going IN to the piece, not in the opposite direction. If you don't want to angle them on the bandsaw I've also done cruder bevels with a dremel tool, or even an upside down belt sander. You just want a very faint taper. It's also a good idea to slightly round off the bottom corners. This can prevent possible damage to your mortise when test fitting and hammering your key in.
Be sure to flip over and trace the TOP of your keys on your work piece, not the bottom, since the top of the key is what is going to line up directly with what you're cutting out. Always score just inside your marks with a marking knife. Rout in steps, as usual. Keep your chisels at 90 degrees when cleaning up your mortise. I chisel the sides first, then the ends and corners. Use the widest allowable chisel, starting with the edge in your mark, and then slightly overlapping each pass.
I make my keys so they'll rise up out of the mortise a good 1/16", the rest can be sanded down after gluing. My keys are usually 3/4" in thickness. Some guys use thinner keys but IMHO to give it more strength I go thicker. Plus if you have a check or something that's visible from the side, it looks cooler to see this thick key going down.
I use a 2-part epoxy and coat the entire mortise. Nakashima was also known to bury a brass screw up from underneath the workpiece into his butterfly keys. I'm assuming this provided even more stability.
Thanks for the explanation, I used this last night came out perfect, can't tell what a rookie I amthis forum is Great !!
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