Angle musings

This week I got a commission to sharpen and repair some knives and one of them was interesting, and it inspired me to write short musings about sharpening angles, respectively about what angle is correct and when.

This is how the knife looked on delivery.

It looks like a small cleaver made by an amateur. It had the proper blade thickness for a cleaver and it was used as such. However, it was unsuitable for that task for several reasons.

This is what the cutting-edge looked like.

As you can see, it was severely damaged and bent. The key word is "bent". At first glance, it was clear that the steel is not too hard and testing with my scratchers confirmed hardness between 53 and 55. That is a bit lower, but still suitable for a cleaver. Hardness alone was thus just a part of the problem. The main part was the grind. The edge had a single-bevel chisel grind at an angle of approximately 18° and that is too steep for any steel and any use except a single-use razor.

Unfortunately, I forgot to take pictures of the renovation process but a few words and a sketch should suffice as an explanation.

Firstly I re-ground the original chisel grind along the whole blade and I polished it to 400 grit. After that, I ground the whole edge on both sides at an angle circa 22° to the central plane of the blade. On the sketch is the state before (up) and after (down). The gray area on the lower picture signifies removed material.

An edge with this profile should be much more resilient and it should serve well as a cleaver for meats with smaller bones like poultry and fish. However, I did not recommend to the customer to use it for beef or pork anymore. For those it is unsuitable as a cleaver for the third reason – it is too small and light.

And when giving the repaired knife to the customer I got a confirmation that it was homemade, crafted from an off-cut from steel for manufacturing cheap stainless shears.