Does anyone make router bits sized to make dado grooves that fit standard MDF thicknesses? Unfortunately, MDF is not sold in nominal fractional thicknesses, as most router bits are.
Carol Reed: Router bit manufacturers make undersized “plywood” bits; however, my experience with MDF is that it is much closer to “standard” thicknesses than plywood.
Richard Jones: It’s difficult to get that just right. You might consider an alternative strategy which I usually use. If your boards are a nominal 3/4″, run a 3/8″ or 1/4″ groove or housing (aka dado) and create a tongue on the joining part to match. You can easily adjust the tongue thickness to suit the groove worked, and you get extra strength due to the interlocking of the returns in the joint, and the extra glue line length.
Michael Dresdner: MicroFence makes a micrometer equipped router fence system that allows you to cut in extremely accurate measured increments. With that fence, paired with a half inch bit, for example, I can cut any dimension groove between one half and one inch in only two passes, and be accurate within one or two thousandths of an inch.