By a modern device on some machines this clamping pressure is instantly variable to suit different kinds of stock and other conditions.
Cutting Sticks
The cutting stick, into which the knife passes after cutting through the bottom sheet, saves the edge from cutting on the iron table.
Correctly designed cutting machines have knife-bar motions that permit no "chug" of the knife into the stick and thus conserve its sharp edge. Many designs, however, are faulty in this respect and the unrecorded expense of their operation is a serious leak.
The cutting stick is set in a slot in the table. The most common and perhaps best form, everything considered, is a ¾-inch square hard maple stick, set so that the knife strikes it ¼-inch from the edge. All four faces of such a stick may be used.
A metal frame for holding a ¼-inch square hardwood stick, or a soft metal (so-called) cutting stick, is made. A round wood cutting stick connected to a timing mechanism which rotates it automatically for every cut, or for a certain number of cuts, is valuable for hard stock requiring microscopical perfection.
The Back Gage
The back gage is moved and controlled on the machine table in several ways. In the simpler machines the gage is attached to a rod under the table, a long slot in the center of the table allowing the connection of the gage with the rod below. The rod is attached to the gage with a worm gear and is operated by a small hand wheel at the front of the table. In other machines the gage is attached to a steel cable, or a metal tape, or a chain which passes over wheels at the back and front below the table.