Fig. 627.
Fig. 628.
Screw or monkey-wrenches are those which have a movable jaw, so that the tool may be adjusted to fit any sized nut within its compass; as shown in Fig. [628]. There are many designs of monkey-wrenches. The one here represented is known as the “knife-handle” on account of the identical construction of the handle of this wrench and that of a pocket knife. It is strong and the shank is extra heavy so that it is hardly possible to spring the jaws in fair use.
Fig. 629.
An interchangeable socket wrench is shown in Fig. [629]. The handle is much like a ratchet drill, having a pawl and ratchet wheel attached to the sockets; these are for use upon various sizes of hexagon or square heads, as represented by figures underneath the handle. Some of these socket wrenches have forms of steel for insertion into the hole in the ratchet by which different shaped and sized bolt heads and nuts may be turned without changing the main socket.
The word wrench which gives this term to the tools here described is one of the strong words of the English language; wrench means, primarily, “a violent twist or turn given to something,” hence, as derived, almost any instrument that causes a twist or torsional strain comes under this heading. A wrench is a tool used by hand to turn or rotate other tools, nuts or bolts.
A wrench is specially designated according to its shape and of the jaws or openings, as an open-end box-wrench, etc. If the opening is through one end, it is termed a single-ended wrench; if it is in the middle, a double-ended or tap-wrench. If the recess is open, it is termed an open-ended wrench; if closed, forming a square or hexagon opening through the metal, a box-wrench. A solid wrench having a notched angular recess in its end, so that any nut or bolt which will enter the jaws can be grasped, is called an alligator-wrench.
The hammer was probably the first tool used by mankind; hammers of stone are found among the remains of antiquity, and these are still in common use among barbarous races. The hammer is made in such a variety of forms that it is almost impossible to classify it; it is named not only for the use to which it is put, but after the trade-class which uses it, as the machinist hammer, the blacksmith-hammer, etc.