A bit of
Flush Cutting
© Frank Ford, 2007; Photos by FF

I've noticed that a spiral cut end mill gives a much finer finish and tends to "grab" less than a regular router bit. In particular, the four flute small diameter milling cutters are particularly easy to work with. They don't come with the handy little bearings that are available for flush cutting router bits, so I've had to improvise a little.

Here's a couple of methods I've used for flush trimming on the drill press, or, as in this case, my Grizzly wood mill.

First, I'll clamp a work board to the table:

And, to make certain that everything lines up perfectly, I'll plunge cut into the work board with my end mill:

This cutter is 5/16" diameter, and it's a size I like to use.

Next, I'll glue a 5/16" dowel into the hole:

Too keep alignment, I bring the quill down to press the dowel into the hole, making sure that the top of the dowel lines right up with the end mill.  Then, to allow just a tiny bit of a safety margin, I wrap a turn or two of masking tape around the dowel:

That way, the bit cuts nearly up to the surface of the work, leaving just the tape thickness of overhang as I make my cuts around the perimeter of the work piece:

Here, I've added 1/4" of mahogany to the top edge of this "peanut bowl" ukulele back.  In the photo above, I'm trimming around the outside, guided by the pin in the table.  But, when I want to trim the inside, I can't use the pin in the table, so I'll have to go to Plan B.

Even simpler and easier than the previous method, I can create a flush cutting bit by protecting part of the cutting edges with sticky aluminum duct tape:

The cutter bites right into the work, while the taped portion skitters along without cutting into the original surface:

Just as with the guide pin, the thickness of tape determines how close I'll trim the work.  Running at 5,000 RPM the tape doesn't hold up all that well, so I need to change it as it starts to wear or flake off.  It took two pieces of tape to do the interior of this ukulele body.



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