How long does a jackknife last? Statistics show the average knife carried by man abides with him only ten months. This period can be lengthened if reasonable care is taken and if the following suggestions are observed for overcoming the general run of knife troubles. By adopting them you can make your own jackknife stand by you a longer period of time than the average.

Fig. 13. - A, B, C, and D show how to make and use a simple graver for initialing a jackknife. E shows the method of grinding down a projecting nub of the blade tang; F, various points into which a broken blade tip may be ground; G, H, I and J, the evolution of a screw driver blade ; K and L, how to tighten a loose blade; .1/. how to make a thumb-and-forefinger grip; and N, where to oil a sticking blade.

Initialing a Knife. If your initials are on your knife, it is more likely to be returned to you in case you lose it. You can make the graver from an old chisel or any good piece of tool steel. Grind the chisel or blade down to the dimensions given at A, Fig. 13, and hone the cutting edge or point on an oilstone until it is keen. Whittle out a short handle, as at B. Outline the initials with a soft pencil or a sharpened piece of soap. Set the graver as at C and push it forward, while, at the same time, you roll your hand from side to side. The rocking creates a series of V-shaped cuts, as at D.

Projecting Blade Points. To remedy these it is necessary only to grind or file off the projecting nub of the blade tang, as at E.

Repointing a Broken Blade. At F are shown four different points you can produce by grinding and honing a broken blade tip. You may find that you will like one of these better than you did the original one. Be careful not to draw the temper of the blade during the grinding process.

Folding Screw Driver. When a pen-blade has been broken off too hopelessly for redemption as a cutting tool as at G, it can be transformed into a neat folding screw driver for light work. Grind off the broken end until it is square as at H, taper the cutting edge and the back edge as at I, and slightly bevel the sides of the blade as at J.

Stiffening a Wobbly Blade. After a knife has been in use for some time, especially in heavy whittling, the heads of the rivets upon which the blades are pivoted often crumble off. The simplest remedy is to countersink the hole slightly at the loose end, then rehead the rivet in the cavity by using a nail set or blunt punch as at K. Another method consists in withdrawing the rivet and inserting a slightly larger one made from a piece of brass wire or a wire brad as at L. This should then be headed at both ends by tapping while the knife rests on a piece of iron.

Providing a Thumb-and-Finger Grip. Sometimes it is desirable to provide a way of lifting the blade of a knife by gripping it with the thumb and forefinger as at M. With a round file, make a curving notch about 1 in. wide in the handle of the knife, reducing both wood and lining plates.

Relieving Sticking Blades. You can usually renew the easy action of a blade that sticks by putting a few drops of kerosene oil between the bolsters and the blade as at N and working the blade back and forth for a few moments. Repeat the process if necessary.