In my original post above, I made an erroneous statement and want to correct it. I said:
- The plunge base has a stiff spring and no fine tuning adjustment. Setting an exact height is difficult.
That statement is incorrect.
Setting an exact router bit height (really, depth) on the plunge router base for handheld edge routing is NOT difficult.
The original statement came out of my inexperience with plunge routers.
Explanation (read: Excuse) that You Can Safely Ignore
I have had the same Black and Decker fixed base router for decades. I did plunge routing with it using the old-fashioned tip-in, tip-out method. I had another router that I gave away, also with a fixed base. I am used to fixed base routers.
I set router bit depths on those fixed base routers using brass setup bars, depth gauges, combination squares, and simply holding the workpiece up to the bit. The routers with the fixed base have nice fine adjustment knobs that make it easy to set a very precise depth and make very fine adjustments to that depth.
My new plunge router bases have no fine adjustment knob like that. I have used the new plunge routers just fine for making stopped dados, finger hold grooves (with a round nose bit), etc. I made jigs for guiding the plunge bases, etc. It all works well. My mistake was not extending that knowledge to how I would set the bit depth for edge routing with the plunge base. It was outside my experience.
For some silly reason, I (stupidly) thought that I would be setting up the plunge base for edge routing the same way as a fixed base, but without the help of a fine adjustment knob. That meant (in my mind) holding the lock lever in one hand while pressing down and up on the plunge base spring until the bit extended just the right amount, holding it in place manually, fighting the plunge spring, while trying to lock the lever. How dumb is that?
I realized during the night that the "right way" is to use the plunge depth stop. It includes a scale on the router, and an adjustable post with finely marked gradations that make it easy to see minute changes in the depth stop setting.
What is obvious to me now
is that you use the plunge stop to set the precise depth. If you want to check the bit depth as I do with setup bars or whatever, you plunge the router to the stop (easy!), lock the lever, and then check the bit. If it needs adjustment, you unlock it and make fine adjustments in the depth stop, then test again. Duh!
Sorry for the confusion, mostly my own. :-(