Carpentry Joinery - Feather Edge
A new stone should not be rejected because it does not work well at first; like everything else, whether animate or inanimate, it has its peculiarities, and its owner will become accustomed to them, and will find that he can sharpen his tools upon his own oil-stone (unless it be a very bad one) better than upon one to which he is not accustomed. He should examine the two evenly, and, selecting that which appears to be the better, he should put a “face” upon it, that is, grind off the rough surface, and make the part of the stone he intends to use quite smooth and flat; this is easily done by rubbing the face of the stone upon a sheet of fine emery-cloth laid upon a flat board; the stone should be held with one hand and moved lengthways, backwards and forwards, without pressing hard upon it, occasionally wiping off the fine dust with his hand, so that he may see how his work is progressing.
So soon as the face looks quite smooth, as if it had been ground all over by the emery, the oil-stone is ready for use, and it may be “ mounted” on a future occasion, but until it is mounted, it should be kept in a box set apart for the purpose, which should be kept clean and free from dust; also, after using an oil-stone, it should never be left exposed upon the bench, nor should thick dirty oil be allowed to accumulate upon it; the face of the stone must always be kept clean and free from dust and grit. A little kerosene will remove dirty oil.
After having put a face upon the oil-stone, the next thing is to sharpen a chisel. In all flat cutting tools, such as chisels, the “front” has the cutting edge and the tool is ground upon the back; some tools, such as axes, which are ground on both sides, have neither front” nor “back” (b). A chisel, after being ground upon a grindstone, has a very rough edge which will not cut; this has to be removed, and a fine edge substituted ; if it were desired to retain the same angle of cutting edge as that left by the grindstone, it would be necessary to place the ground part of the chisel fiat upon the oil-stone, and rub it backwards and forwards until sufficient metal had been worn down to remove the whole of the rough edge; this would take a very long time, because the oil-stone cuts very slowly; it is therefore found better to obtain a more obtuse angle for the cutting edge than that left by the grindstone.
After rubbing the chisel upon the oil-stone for a short time some oil will have accumulated in front over the edge. Upon feeling the front of the chisel with the finger there will be felt at the edge at a (Fig. 2) a slight burr; the chisel should now be turned over, the front pressed quite flat upon the face of the oil-stone, and moved about an inch once or twice backwards and forwards. Upon feeling again with the finger the burr will have disappeared—if not, the front of the chisel must be again rubbed a little upon the oil- stone in order to remove the burr.
The oil will next be wiped off the chisel with some shavings, and the feather edge will become visible this feather edge is an extremely thin plate of steel, in fact, so thin that the oil-stone has been unable to cut it away, but it must be removed, otherwise, it will blunt the chisel immediately. The best way to remove this feather edge is to hold the chisel by its handle in the right hand, and to slap the edge smartly, first one side, then the other, across the palm of the left hand.
This can only be taught to the amateur by a man who is in the habit of doing it—no written description is of any use, nor is instruction from a man who has only seen it done by others and “knows how it is done” any better. At first great care must be taken, or the result will be a very serious cut; it is best to practice with a screw-driver or a very blunt chisel, and then begin to do it slowly with a sharp chisel. Men may often be seen to do this very carelessly, and it appears a wonder that they do not cut their hands to pieces, but good workmen never cut their hands, it is only bad workmen who cut their fingers. When the feather-edge has been removed the chisel is sharp, and should be able to shave off a hair from the back of the amateur’s hand.
In order to obtain a feather edge, which is rubbed upon the oil-stone, must be flat; if it be even slightly rounded, it is impossible to get a good cutting edge, in other words, the chisel is blunt.
The whole art of sharpening a chisel or other tool consists in being able to hold it at the desired angle upon the oil-stone, and to work it backwards and forwards without altering that angle; this can only be acquired by practice, and when once it has been acquired, it becomes a habit, and it is never forgotten or lost. The oil-stone should be placed at a convenient height (usually upon the joiner’s bench) straight in front of the person, who should hold the handle of the chisel in his right hand, the back up, and the fingers underneath; two or three fingers of the left hand should be placed upon the front of the chisel, according to the amount of pressure required, and, with the elbows stuck well out from his sides, he should try to work the tool backwards and forwards without varying the angle; when he has succeeded in obtaining the burr for the feather edge, he has made great progress, and the rest will be easy; if he keeps his elbows down to his sides, he cannot sharpen his chisel.
The face of the oil-stone should be kept clean and covered when not in use; there should be a few drops of oil upon it when sharpening a tool—olive oil does very well—and care should be taken not to scratch the face with the corner of the tool. Sprig- bits and such like very narrow tools are best sharpened upon another oil-stone or across the ends of the oil-stone used for chisels, so that there may be little risk of injuring the face. If the oil-stone be kept in good order, there will be no trouble about sharpening the tools, and with sharp tools work is made easy.