The ordinary wood-worker's dividers can be bought in many forms, the most common being the screw-adjusting wing dividers, shown in Fig. 57. This form is reliable, and is easily adjusted to the required distance between points. Moreover, when damped by the thumb-screw, it is not liable to be altered by a slight blow in handling.
Another and improved form is shown in Fig. 58, one leg of which is removable so that a pencil can be inserted. This will be found very convenient for marking and laying out work.
For spacing the teeth of gear wheels, and for other work in which great accuracy is required, a pair of 2½-inch or 3-inch dividers, such as are shown in Fig. 59, will be found necessary.
The trammel is used when the distance between the points to be reached is too great for the ordinary dividers. The trammel points are clamped to a beam of sufficient length to enable them to be set to the required distance apart. They may be bought with one adjustable point,as illustrated in Fig. 60; or without the screw adjustment, as in Fig. 61. The points are removable for the insertion of a pencil socket and pencil when needed.
For very accurate work, an excellent tool of this kind is illustrated in Fig. 62. The beams furnished are 4 inches and 13 inches in length. By the use of the cone center, shown at V, which may be substituted for the regular point, the tool can be used for scribing a line around any hole already bored - which is sometimes a matter of great convenience. The complete set includes the pen, pencil, straight and bent points, and the cone center, as shown in the cut.