Old Methane Gas Cloud
Join Date: Jun 2009
Location: Huntington Beach, California
It's not all that complicated.
The stiles are the vertical size of the door. Consider overlay or inset in your measurement.
The rails have to account for the part that is mortised into the stile. First measure the horizontal opening for the door. Consider overlay or inset in your measurement. Subtract double the width of the stile from this measurement. This is almost the length of the rail.
Measure from the bearing surface to the out most cutter on the stile router bit. Double that measurement and add that to the length of the rail determined above. In all probability this measurement is 7/16" and when doubled is 7/8".
If you are doing inset doors, you'll probably want to add 1/8" to both the horizontal and vertical measurements. That way you can trim the doors on the table saw for an exact fit.
BTW - I doubt that you'll ever find a "perfect" rail and stile router bit set. When you look at the joint of the rail into the stile there will be a small gap of the stub tenon. (1/128" or so) It's just the way that the bits are made. If the stub tenon were 1/128" long, the gap would be on the front of the door. I think that sets for a shaper are made to a tighter tolerance.
Use the right tool for the job.
Rich (Tilting right)
Huntington Beach, California
Remember that when we have the "BIG ONE" everything east of the Rockies falls into the ocean.