Safety considerations
There are at least two schools of thought on the safest and most effective method of sharpening.
Some people maintain that the best results are achieved by running the file or stone towards the edge, and that this minimises the creation of burrs. If sharpening is done this way, the hand holding the file or stone must wear a protective leather glove, as the risk of cutting one’s hand is high.
Other people maintain that there is no advantage in sharpening towards the edge, and that it is safer and just as effective to only sharpen with the file or stone run- ning away from the edge. In this case it is not so essential that a glove be worn on the hand holding the stone, although accidents can still happen. With practice, it is also possible to learn to use the stone in either hand, in which case the tool can always be held with the blade facing away from the body.
It is recommended here that beginners should learn to sharpen by running the file or stone AWAY from the edge, and that a glove should be worn on the hand steadying the file end, or holding the stone. If possible, clamp the tool in a vice, so that either or both hands can be used on the stone or file. Never use a file without a handle, or there is a risk of the tang causing injury to the wrist and forearm.
A file cuts on the forward stroke only, and should be lifted off on the return stroke. Rubbing it back and forth will cause it to become blunt much more quickly.
A leather glove is cumbersome and stiff, and it makes your hands clumsy and grip weak and is therefore not recommended for tool sharpening. There are many different grades of gloves available today and the purchase of ‘cut resistant’ gloves that allows for greater dexterity is recommended. Ideally, each person should have their own sharpening glove or gloves, which then harden to the shape of the hand.
Always wear goggles, hearing protection and gloves when using machine sandstones, bench grinders or angle grinders. These machines must only be used by operators who have received general training in their safe use, and specific training in their use for tool grinding and sharpening. Particular care must be taken when using angle grinders, which are hand-held, and with which there is less margin for error than with a bench-mounted machine.
Tool use
You should have, and know how to use, the tools listed here for sharpening.
A 260mm (10”) mill file with one rounded edge is the best tool for filing off metal in quantity, and gives greater control and is quicker to use than a coarse stone. Finish the edge with a fine stone.
Make sure the stone is clean and free from grit before you use it, or you will damage the edge of the tool. Lubricate with vegetable oil or water. Don’t use old engine oil as this contains harmful detergents and impurities such as bits of metal which can damage the stone or tool. As you work, wipe away any surplus oil off the stone and blade with a rag. As the blade becomes sharper it will ‘bite’ into the stone, and the feel and sound of the blade on the stone will change.
If a sharpening stone becomes concave with use, it can be rubbed on a sheet of glass lubricated with oil and fine sand or grinding compound until it is flat. use a small disused window in a sound frame, with the glass sup- ported from beneath by a piece of wood or board, to avoid accidents. Fine sand and oil only work on natural stones such as Turkey, Washita or Arkansas. Artificial stones such as silicon carbide (carborundum) need a mixture of oil and silicon carbide powder or valve grinding paste.
Whatever you use, rubbing a stone flat is a daunting task, and it may be more cost effective to buy a new one.
It is well worth making up special jigs for holding tools during sharpening. The jig is clamped in the vice, holding the tool firmly and safely, and leaving both hands free for sharpening.
It is usually best to stand at the work bench, with legs apart and body over the work. The shoulders and upper body provide the pressure, while the arms and hands provide motion and accuracy.
Machines must only be used by trained operators. It is very easy to damage the edge of a tool by careless grinding, or to ruin the temper of a tool by letting it overheat. If the cutting edge turns blue, it has lost temper and will be impossible to sharpen. If this happens, you must grind off the blued areas and start again. Machine sandstones, bench grinders and angle grinders are described here. The choice of which machine is used will depend on availability, the type of tool and amount of grinding to be done, and the preference and experience of the operator. Some operators prefer to use a bench-mounted machine, whereas others may like the flexibility of a hand-held machine. In skilled hands, an angle grinder is effective for most grinding jobs on billhooks, axes, mattocks, picks, crow- bars, bolsters and cold chisels. Use a fairly coarse abrasive pad in new or good condition. Care must be taken to keep at least 2mm from the edge of the blade, and to keep the abrasive pad moving along the whole length to be dressed. Lift it off at the end of every length to inspect progress and allow the blade to cool down. Finish off with a file and sharpening stone when the worst has been dealt with.
