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Trail Construction and Maintenance Notebook

Tools (continued)

Tools for Sharpening

About Sharpening—Inspect all tools before use. Sharpening makes tools last longer. A small scratch that is ignored could lead to a serious crack or nick in the blade.

Use a file or grindstone to remove metal from the edge. If there are no visible nicks, a touchup with a whetstone will restore a keen cutting edge. In these instances, you need only restore the edge bevel. Whetting the edge removes very small bits of metal from the blade and causes the remaining metal to burr slightly on the cutting edge. This burr is called a feather, or wire edge. Remove this weak strip by honing the edge on the other side. The correctly honed edge is sharp, does not have a wire edge, and does not reflect light or show a sharpening line. Wear gloves when sharpening cutting edges.

Restoring the blade bevel requires coarser grinding tools to reshape worn cutting blades. Reshape blades with hand files, sandstone wheels, or electric grinders. Remove visible nicks by grinding the metal back on the blade. Remember that the correct blade bevel must be maintained. If the shape can’t be maintained, have a blacksmith recondition the tool head or discard it.

If a cutting edge is nicked from a rock, it often is work hardened. A file will skip over these spots and create an uneven edge. Use a whetstone to reduce the work-hardened area, then resume filing. Alternate the two until the file cuts smoothly over the entire length of the edge.

Files. Files come in single or double, curved, or rasp cuts. Single-cut files have one series of parallel teeth angled 60° to 80° from the edge; they are used for finishing work. Double cut files have two series of parallel teeth set at a 45° angle to each other; they are used for restoring shape. Curved files are used for shaping soft metals. Rasp cut files are used for wood.

Files are measured from the point to the heel, excluding the tange (the tip used to attach a handle). Length determines the coarseness of files. There are generally three degrees of file coarseness: bastard, second cut, and smooth. The bastard will be the coarsest file available for different cuts of files of the same length. A 254-mm (10-inch) mill bastard file is good for all-around tool sharpening.

Before filing, fit the file with a handle and knuckle guard. Always wear gloves on both hands to prevent cuts from the sharpened edge. Secure the tool so both hands are free for filing. Use the largest file you can, depending on the size, nature, and workable stroke length of the job. Remember that files are designed to cut in one direction only. Apply even pressure on the push stroke, then lift the file up and off the tool while returning for another pass.

Store or transport files so they are not thrown together. Protect them from other tools. An old piece of fire hose sewn shut on one end makes a great file holder for several files, a guard, and handle. A hand-tool sharpening gauge that gives you all the correct angles can be ordered from the General Services Administration (GSA).

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