Excerpted from “The Essential Woodworker,” by Robert Wearing.
In order fully to understand the workings of the metal plane it is a good idea, particularly for the beginner, to strip down the plane to its smallest component. If you have an old or secondhand plane this is a good opportunity to renovate it. Even if the plane is mis-assembled and maladjusted, no damage can be done to it. Figure 1 shows the structure quite clearly and gives the correct names to all the components. It will be seen that there are three distinct adjustments.
The depth of cut, that is the thickness of shaving removed, is controlled by the cutter adjusting wheel. The wheel running up and down a left-hand thread operates the Y lever. This in turn engages in the Y lever socket of the cap iron (or breaker), which it moves up or down. The blade is secured to the cap iron and is moved by it.
The second adjustment is lateral. The lateral lever has a circular stud at its end. When the plane is assembled it must be made certain that this stud fits into the slot in the blade. Movement of the lever thus moves the cutting edge sideways, preventing one corner from digging in.
The third adjustment is commonly called closing or opening the mouth. The whole frog is moved forward with the blade and the effect is to alter the size of the gap in front of the blade. The lever cap screw should be just sufficiently tight to make sideways movement of the blade with the fingers difficult but not impossible.