How tight is the throat (mouth)?
This question seems to come up immediately whenever a particular plane is being discussed. In fact, if an extremely tight mouth was always a good thing, then all of these planes would have one. After all, these planes were hand fitted, and any throat size desired could be achieved. For the finest work, a gunmetal plane with a super tight throat can’t be beat. However, this comes with a price. The plane must be set to take a super fine shaving, and the work can be very time consuming. That is why a Norris A5, the most common infill smoother, does not have a particularly tight mouth. The A5 is designed to be practical over a broader range of work, and in all but the most unusual cases, will do work equal to a plane with a tighter mouth, such as an A17. Conversely, the A17, Norris’s top-of-the-line smoother, is useless for most work. Other factors that are critical are the weight of the plane, the pitch of the blade, the quality of the cutter, and the how well it is sharpened and adjusted
