Depth Adjustment, Plunge-Base
There are two methods for controlling cut depth with these tools in the plunge configuration: depth gauges and upper-travel limiting knobs (none of these routers is equipped with a true micro-fine adjustment that you'd find on a high-end plunge router).
Depth Gauge. The depth gauge on a plunge router is really a combination of two elements?the depth rod and turret stops?which combine to determine and limit the cut depth. The depth rod adjusts the intial cut depth; the turret controls a series of subsequent cut depths, required in any multi-step operation like cutting dadoes or mortises.
Bosch and DeWalt equip their depth rods with depth-adjustment knobs that enable you to set rough depths and then dial in the exact cut depths with the adjustable knobs. Good idea, but we found them difficult to operate. Bosch's depth-adjustment knob was hard to turn because there isn't much space around it for your fingers. The DeWalt depth-adjustment knob was even more problematic: It's located on the end of the depth rod, where it contacts the turret stops and might be accidentally rotated by the movement of the turret, potentially changing cut depth.
Upper-Travel Limiting Knobs. The Porter-Cable and Makita tools have upper-travel limiting knobs on their plunge bases. These knobs are useful when the tools are mounted in router tables, because the knobs act somewhat like micro-fine adjustments. Rotating them raises or lowers the bits accurately; however, for handheld plunge-routing functions, an engaged upper-travel limiting knob can stop the motor from rising high enough to extract the bit entirely from the workpiece. In other words, the bit stays partially exposed below the base plate and could strike the work piece or template while removing the tool.
While the Bosch, DeWalt, and Porter-Cable depth rods are smooth, Makita's is threaded. The threads facilitate good fine adjustments above or below the table?one knob revolution equals 1/16 inch?but substantial depth changes, say 1/2 inch, are tedious. Porter-Cable has no fine adjustment on its depth rod.
Depth Adjustment, Fixed-Base
In the fixed-base configuration, the Bosch unit uses a true one-step micro-fine adjustment knob, and it works very well. According to Bosch, it's accurate to 1/256 inch. DeWalt's depth-adjustment is a ring that surrounds the motor.
It's different but works equally well. The company says it's accurate to 1/64 inch. While we didn't measure accuracy with a micrometer, we were able to dependably set a measurement on each tool, say 3/8 inch, change the setting, then go back to 3/8 inch with no problems.
On the Porter-Cable and Makita routers, you make depth measurements and adjustments by first lining up a ring gauge, marked in 1/64-inch increments, with a hash mark on the motor housing. Then you rotate the mark on the motor to your desired depth. This system has been around for years and works well enough, but the two-step process is not as efficient as the Bosch and DeWalt systems.