Perhaps of all cutting instruments, the razor possesses the most general and personal interest, in respect to the conditions required for its perfect action, and it is therefore proposed to notice at moderate length the principal circumstances on which the perfection of its edge depends.

The razor notwithstanding the peculiarity of its outline, conforms strictly to the ordinary wedge form section of most cutting tools, but as it requires the most delicate edge that can be produced, it is so formed as to facilitate to the utmost the process of sharpening. For instance in the plane iron, chisel, penknife, lancet, and most other instruments, the angles of the one or both the sides of the wedge or cutting edge are determined by the particular inclination at which the tool is held upon the stone, but if the hand wavers, the setting or facet instead of becoming a plain flat surface, becomes rounded and ill defined.

In the razor on the other hand the proportion between the width of the blade, and the thickness of the back, is almost always such that when the blade is laid perfectly flat on the hone, or so that the edge and back both touch, the suitable angle is obtained, and which varies from about 17 to 20 degrees; the exact measure of the angle is very little studied, although in reference to the principle of cutting tools some little variation ought to be made, in choosing the thickest edge for the strongest beard. It does sometimes happen that the razor is not laid quite flat on the hone, but that it is slightly tilted, this occurs when a wide razor that has been ground on a large stone is required to be sharpened for a stiff beard; but it so rarely occurs that the razor is placed otherwise than flat on the hone, that the exception may be overlooked.

The magnified sections of razors in figs. 1031 to 1036, which for distinctness are drawn three times their full size, and for comparison, of the same angle or 18 degrees throughout, exhibit various modes adopted to avoid the necessity for sharpening the entire side of the imaginary wedge, represented by the dotted lines, by hollowing the sides in different ways. It is apparent that it would be much more tedious and difficult to wear down the imaginary flat sides represented by the dotted lines, than the small portion of the same which are supposed to remain; and indeed the entire dotted line if sharpened, would most probably become rounded instead of flat. The concavity therefore facilitates the placing of the razor on the hone, it thins the edge leaving but little for the stone to abrade, and it prevents the finished appearance given to the sides of the razor being detracted from by the sharpening.

Figs. 1031 and 1032, represent the section of that description of razor blade which is by far in the most common use, as before observed the widths of the blade and the thicknesses of their backs are such as to give in each an ultimate edge of 18 degrees when the blade is sharpened on the hone, but fig. 1032, is ground transversely on a wheel of four inches diamater, and fig. 1031, on one of twelve inches, the general extremes of curvature. It is clear that the former possesses an edge that is thinner and more flexible, and that presents a narrower edge or plane to be abraded by the hone; and which latter in consequence will cut with greater precision and delicacy than if it had to abrade the entire surface. The curvature in most general use for best razors is intermediate, or from 5 to 6 inches, but stones of from 12 to 15 inches diameter are from motives of economy resorted to for common razor blades.

Figs. 1031.

Section III Setting Razors 3005

1032.

Section III Setting Razors 3006

1033.

Section III Setting Razors 3007

Figs. 1034.

Section III Setting Razors 3008

1035.

Section III Setting Razors 3009

1036.

Section III Setting Razors 30010

In some few cases the edge of the razor is ground lengthways on the stone, so as to become nicked in, in the manner represented in fig. 1033, and in this way any degree of thinness may be given, and also extended throughout any desired width. This mode of grinding the razor is however more difficult, and the feebleness of the edge may be thereby easily carried to excess; and from the vibration to which they are liable when applied to a strong beard, they are called by the Sheffield cutlers, rattler razors.

Sometimes the two methods of grinding are combined, as shown in fig. 1034, in this case the razor is first ground transversely as for fig. 1032, and it is subsequently ground lengthways so as to be nicked in for about half its width; these razors are known by Sheffield workmen as half rattlers. For the sake of variety the longitudinal grinding is sometimes only extended about one quarter of an inch from the edge.

Other razors as in fig. 1035, are made as very thin acute blades fixed in a detached back somewhat like a dovetail saw, in this case the edges of the blade and of the back are simultaneously whetted on the hone; but no advantage appears to result from the construction, on the contrary the blade cannot be reground without removal from the stock, which implies the risk of its being reduced below the edge of the stock so as to prevent its replacement.

Fig. 1036 represents another of the modes in which razors are occasionally constructed, in this a loose frame or guard of brass is added to the blade. The idea in this case is to prevent the liability to accident incurred by nervous or infirm persons from the tremor of their hands. The frame is intended to act as a muzzle or guard to prevent the edge penetrating to any serious depth, and the instrument is known as a guard razor.

The keenness of the edge of the razor is commonly tried by-making a faint incision in the thick skin covering the inner edge of the palm of the left hand, but the cutler also tries the razor upon the thumb or finger nail. The razor is either placed in a line with the finger and obliquely across the end of the nail, or a still more sensitive test is to place the blade at right angles to the finger, and allow it to rest upon the back of the nail, that of the third finger being by some considered the most sensitive. In this manner a very minute notch in the edge is quite perceptible, and the keenness may also be appreciated by the degree in which the razor hangs to the nail, as the keen blade will make the deeper incision, and appear to offer a more dragging yet smooth resistance, whereas the blunt razor will slide over with less penetration and drag.