Knives general info

KNIVES – Basically there are two different materials for knives, steel and ceramic.

Ceramic knives, usually white in colour, are made from similar clay to porcelain.

This material makes for a very rigid blade which will snap if bent too far. However, it does give a glass-hard, super-sharp cutting edge which will keep sharp for many years,  outlasting  any metal blade I know of. The trade-off here is in the hardness. You cannot use this type of knife for heavy chopping of bones or wood.  It will just chip the blade, which is almost impossible to repair and destroy an expensive knife.  For sharpening, these knives would probably need returning to the manufacturer, or some kind of diamond coated abrasive. You should expect a ceramic knife to keep its edge for many years

Some manufactures have reduced manufacturing cost by making blades of ceramic-coated steel which gains the strength advantages of steel but after the paper-thin ceramic coating is worn away you are left with a steel blade.

Steel knives are the most durable.  There are many types of steel but they divide into two main groups, Stainless and Non-stainless or what is known as Carbon steel.  Knives made from non-stainless steel tend to be cheaper and need a lot more care.

GRINDS – Knives with thicker steel blades tend to be hollow-ground.  This can give a very thin edge, which is good for cutting as it lets air into the cut, creating less friction, so that the material doesn’t stick to it so easily.  Also, if the blade if narrow, the best way to get a fine edge is to choose one which is hollow-ground.  It is also easier to resharpen.In cross-section, a hollow-ground blade is concave, curving inwards, not wedge-shaped, like a flat-ground knife, which can be difficult to edge.

Commercially, hunting and skinning knives are often hollow-ground because they tend to be made from thicker steel but the drawback here is that the edge can break from heavy chopping.     The other common type of grind is the flat-grind.  This gives a wedge-shaped edge like an axe, which works very well on wide blades such as kitchen knives and on thinner section steels such as boning knives.

It is not so common in hunting knives and tends to be more difficult to resharpen as the knife gets worn.  For this reason it is only used on steels of 4mm thickness or less.  As the edge wears, it obviously gets thicker the further up the blade you get.  The steel tapers from the point to the guard of the knife, as well as from the top to the cutting edge.

Incidentally, most old swords are flat-ground for the purposes of strength.     There is a lot of talk about edge angles.  Basically, the wider the angle, say 15,degrees the more the edge is suited to heavy work.  The thinner the angle, say 5, the better it is for fine cutting.  In other words, the difference between a cleaver and a razor- blade.

SHARPENING – There are a lot of different tools for sharpening knives.  Some work well, others are desporate.  The edge-holding on the wide angle edges lasts longer but they are harder to sharpen and, as I’ve said, don’t cut as finely because of the friction.

A good oilstone is one of the best and easiest ways to edge a knife.  Arkansaw is a good make.  There are other artificial stones available.  Lansky and Spyderco are good and for some steels that are very hard and tough, the artificial diamond-coated stones are great.

To sharpen any knife, you start by putting a bevel on each side of the blade, that is, an angle, which in cross-section looks like a small triangle.  The apex of the triangle is where the knife does its cutting.

When you sharpen a knife, you are sharpening the angles on each side of the bevel, which makes a little burr of metal from your sharpening along the cutting edge.  This is called a wire edge.  You can get rid of it by either stropping the edge or polishing it on a wheel, which gives it a smooth, razor-sharp finish, such as is used for surgical instruments.  However, the wire edge, being a bit rougher is much better for cutting anything wet and is rather easier to re sharpen.  It only needs a couple of rubs to make it stand up again.

Another thing that affects the edge of a knife is the hardness of the steel.  What you are looking for is a hardness of 60RCS.  This does make for a hard steel but if the metal is of good quality, it won’t make a huge difference to its tensile strength.  On some of the better-quality hunting knives you will often see the Rockwell mark, which is a little dent on the ricasso.  The ricasso is the flat area just in front of the guard or bolster.

HANDLES –  These days you can choose from many kinds of handle, metal, resin-based (like Micarta and Tufnol), wood such as ebony and rosewood and horn,  fossil ivory or stag horn.  It is a good idea to consider how much you are going to use the knife and for what purposes.  Wood can be just fine if well-seasoned. Resin-based materials are excellent for hard use.

Knives in particular kitchen knives also come with a textured stainless steel handles and often appear to be made of one piece of metal in fact the handles are often welded on to the blade and while this makes for a knife which is very easy to clean the welding process can effect the blade steel this becomes apparent only after some years of use. What you see are little black specks ( carbide drop out) running down the weld area on closer inspection they can be seen to be square in shape and can weaken this high stress area of the knife.

Leave a Reply