Flat chisels are available in stores. If the quality of steel or the size of flat chisels does not suit the carver, then a flat file or personal files can be used with complete success, starting with the narrowest one. They are sharpened without preliminary annealing (by heating) on a sharpening wheel or a water sharpener. In the first case, the sharpened chisel should be constantly dipped in water. It is not necessary to bring the sharpened end to a sharp blade, because it is difficult to keep an eye on it so that it does not burn at high revolutions of the wheel. The appearance of discoloration is a sign that the tool is spoiled. In this case you need to harden the tool again or remove the burnt area on the wheel and sharpen the tool again. It is better to sharpen the blade to the required sharpness manually on a hard bar.
Considering this, it is useful to pre-select the middle of the chisel surface to be sharpened with the sharpening wheel, so as not to rip it off manually afterwards, but to work only with the tip of the chisel.
The notch of the file on its end should be removed with a circle, all around the perimeter, and the longitudinal ribs smoothed, so they do not cut your hands.
Small tools for carving are more convenient to grind in the process of manufacture on a hand drill with a sharpening wheel inserted in it.
The angle between the planes that form the cutting edge – blade should be about 15-20°. The end of the chamfered chisel will be 3-4 times its thickness.
Cutter will be useful later and another chisel width of 20-25 mm, which has a sharpening angle is less sharp (20-25 °). Such a chisel is designed to work by hitting it with a mallet, or for roughing work, when you need to remove a large mass of wood while moving the chisel forward, tilt it down with force, as a lever. In this case, the too sharp and brittle chisel blade will break, and the more plastic blade will bend.
All straight chisels, especially the medium and wide ones, have rounded blade corners. Straight chisels with well-defined angles are used only in geometric carving. The blade line should be slightly convex.
It is desirable to have 5 and 8 mm wide chisels, made respectively from a file and a screwdriver, roundly sharpened, with a strongly convex cutting edge and ground corners. They are convenient for working in narrow and deep grooves of the workpiece. The same chisel, but with a wider blade, is also useful when working with a mallet, when the workpiece is given a rough shape for a future carving.
After the chisel is ground clean by hand on a rather hard block. In this case, it is necessary to adhere to the rule: to drive the entire cut surface of the chisel (chamfer) on the bar, do not increase its angle, i.e. do not raise the handle out of a desire to sharpen the cutting edge as quickly as possible. This mistake will lead to a loss of the sharpening angle and a decrease in the cutting qualities of the tool. For the same reason, a beginner should not be advised to sharpen the tool by weight, holding the bar in his left hand.
The hand movements when sharpening the chisel can be circular or at an angle to the blade, first tilting to one side and then to the other. The latter method is convenient, as it allows you to see which place is being ground by changing the direction of the strokes on the chamfer. It is necessary to avoid movements of the chisel in the direction along the blade or against it. The recommendations available in the literature on sharpening the tool by rotating the grinding wheel or moving the chisel along the bar in the direction towards the blade to get rid of the burr are applicable only for coarse sharpening.
The emergence of a burr – a bend of a narrow shiny strip of blade on the front side – is a sign of sufficiency of sharpening. The chisel is turned to the other, front side, which is also ground by touching all points of the plane with the stone. After that, several repetitions of grinding are made on both surfaces of the blade: with each turn of the chisel, the hand movements become lighter and more frequent – and so on until the burr disappears. When sharpening the chisel, you should not forget to round the corners of the blade.
Further finishing chisel (dressing) is better to do on the donkey or filling the board length 25-30 cm and section 5×1 cm, sheathed round fine sandpaper (preferably emery cloth) at the butt edges of one of the edges of the board. Practice has shown that it is not necessary to use polishing paste (or chromium oxide oil paint) for the final tool dressing. In the process of work on the dressing board will appear smoother and fresher-harder places, which will allow using the same sandpaper on the board for sequential sharpening: from coarse to clean. As with a burr, counter-blade movements should be avoided. The front side of the chisel should also be polished to a shine. The last dressing movements should be made only towards yourself, somewhat at an angle to the blade line, up to 45°, both to one side and to the other. Then a test carving should be made by testing the chisel in various ways, especially across the fibers of strong wood. It is quite likely that in doing so, the chisel blade will “sit” and not give the desired result. This is not always a sign of bad steel or sharpening. You need to tuck it in again, or even a third time, and check it until the cutting edge settles.
It is hardly likely that the steel of a hand file or a personal file is weak. The cause of a poor tool can only be improper sharpening’.
A well sharpened chisel lasts a long time and does not require frequent refilling. Only after hours of work you need to adjust it. In order to achieve the result sooner, if the chisel has been in use for a long time, it is possible to slightly raise the handle when dressing – to strengthen the contact of the sharpened blade with the bar, given that during the initial sharpening its sharpening angle was quite sharp. In this case, a secondary chamfer is formed, which gives an angle of 20° at the blade, which practically suits the cutter in his work. Naturally, after some time it will be necessary to correct the blade sharpening angle again on the bar, or even on the wheel of the hand drill (Fig. 105). This will be the test of the tool when the cutter finishes his next job.
Do not use a chisel made from a file as a file: you can cause yourself a dangerous injury by the cutting sting.
If you do not use a straight chisel with a sharp sharpening angle under a mallet, do not use it as a chisel or scraper to smooth out the surface, it will cause the blade to deteriorate and take a long time to resharpen.