Good Idea:  "Making dados to fit any width panel."

	We all know that a 3/4" thick piece of plywood is rarely 3/4" thick. Router bit manufacturers have made "undersized" bit sets just for this reason, but chances are good that they won't fit exactly, either. The problem is that these panels will vary and they can even vary from board to board. You can go nuts because of this, or you can learn this quick and very accurate way to make exact dados. I have been using it for years now (but that is not to say I am not nuts.)
I asked Andrea to rummage through the scrap bin and find several examples of 3/4"  stock. She measured each and found quite a variety. The Lyptus was a full 7/8", the MDF was 3/4", a piece of plywood was almost 1/8" less, and the 3/4" pine was 13/16".
	She uses a 3/4" straight bit to view the discrepancy. It is hard to tell this way but if we make dados using this bit, the various samples will not fit.
To start my procedure, Andrea starts by installing a 1/2" straight bit. We could also be using a 1/2" up-spiral bit. The very same procedures would be used. We will be using the Festool OF 1400 router.    Andrea asked why we use a 1/2" bit rather than something closer to the final dado. My answer is that since we need to make the dado in two passes, we can use any smaller bit we want. The 1/2" bit just makes for an easier first pass since we will be removing less material.
	She plunges the router until the bit just touches the workpiece and locks it at that point.
She then uses a 3/8" spacer and locks the plunge stop to this depth.  I like to make dados 1/2 the thickness of the board itself.
	Now Andrea installs a guide rail system that we have put together from other Festool accessories. The large knobs allow us to adjust and tighten the stops at points along the edge guide rods. Her left hand is on the nut that locks the rods in position on the router.    We will be using the Festool guide rail system in this example.  The method can also be used with other routers using a clamping straight edge.    See also my review of a year or so ago of the Accurate Guide.  Here: "New Product:  "The Accurate Guide" for Precise Dados and Sliding Dovetails "
She will first set the router guide so that the first cut is 3/4" away from the guide rail. This is somewhat arbitrary but works well for us. The rail is clamped to the workpiece. This would also be a wonderful use for the MFT, but there are times (like now) when the work table is more accessible.
	Andrea uses the outside stop to move the router closer or further away from the guide rail. The inset shows the view she has of the router bit aligned to the pencil mark she made.  Once that is set, the outer knob is untouched so that the router can be positioned at the 3/4" mark without sighting or marking the line.
To this point, she has made all her adjustments with the dust extraction and power connection not made — a great safety feature. Now she can connect these. They are coming down from the boom arm.