Knife types

Knife types

There are three types of these knives, SP (tool steel), HSS (high speed steel) and TCT (tungsten carbide). As a rule of thumb: if you are going to machine less than 200 linear meters (656 linear feet) of lumber you can use SP knives. If you are going to machine more than that, mill across the grain direction or machine very hard wood types, you should use HSS knives.

SP, tool steel, also called carbon-steel

SP steel is hardened by heating and cooling. SP is used when you are only going to mould a small amount of boards. It is cheap, but can lose its sharpness already after 300 linear meters (980 linear feet). Among other things, it is the heat which is produced when molding that makes the knife dull. SP can stand 300ºC (572ºF) before it is damaged. The cheap knives that can be found in various catalogs and in hardware stores are made of tool steel and should not be compared with HSS.

HSS, high speed steel or cobalt steel

In most cases, this is that quality of steel that we recommend. It is about twice as expensive as SP but, on the other hand, it keeps its sharpness for at least 2000 linear meters (6560 linear feet) which makes it cheaper in the long run. HSS can stand 700ºC (1292ºF) without being damaged.

TCT, tungsten carbide, also called cormant

This is the most durable type of knife. The hardness of the tungsten carbide makes it brittle like glass. Due to this, you cannot sharpen the edge with as sharp angle as when sharpening HSS and SP, which makes TCT cut somewhat less effective through some materials. TCT costs 8-10 times more than HSS, but it stays sharp for up to 6000 linear meters (19680 linear feet). TCT can stand 1000ºC (1832ºF) without being damaged. Remember to handle the TCT knives with care. Always place the cutter on soft bedding.