The Jack Plane (fig. 55) is used for the first dressing of timber, but with care it can become the instrument for finer work also, especially if the wood operated on be originally fairly even in surface, and the iron very sharp.

The body of the plane is usually about 16 1/4 ins. long, 3 ins. wide across the face, and 3 1/4 ins. deep. The iron is 2 1/4 ins. wide.

The mouth of the plane is about 5 1/2 ins. back from the front end of the block, and is about 1/16 of an inch wider than the iron that fits it, making 2 5/16 of an inch. This leaves 1/3 1/2 of an inch on each side of the mouth for the sides of the escapement.

Fig. 55.

The illustrations show the general shape of a jack plane.

The handle, or toat, should be mortised into the body well forward near the back of the iron, in order that the downward pressure of the right hand that holds it may be nearer to the cutting portion of the plane, and therefore have more power. It will be found, too, that if the handle is set further back in the block, the back portion of the hand cannot lie comfortably on the top of the plane. The bent form of the handle is useful for either pressing downwards and forwards, or for lifting the plane, which is often necessary to cut or break a shaving. The projection at the top of the handle is also of much assistance in this lifting of the plane.

The cap-iron is never set back from the edge of the cutting iron more than 1/16 to 1/8 of an inch, and this latter is never allowed to project more than of an inch from the face.

Jack planes for boys should be slightly smaller than those for men; the dimensions are 16 ins. long by 2 3/4 ins. wide, with a 2-in. iron.