Saws with hardened teeth

 

— a feature of hardened teeth (usually they have a characteristic dark colour that differs from the colour of the blade) is a very high hardness. On the one hand, thanks to this, the hardened canvas does not dull for a long time — many times longer than usual; on the other hand, it is impossible to sharpen dull teeth on your own, you will have to change the worn blade (or even the entire hacksaw).