© 2019 by Steve Pellegrino. All rights reserved.

methods of the craft

Profiling & pre-grinding

My work begins when I receive bars of steel from my supplier. The knife design is transferred to the steel using a contrasting marking fluid and a scribe. From there, the profile is cut from the steel sheet and is ground up to my scribe lines. 

Next, any necessary holes are drilled while the steel is soft, and pre-grinding is performed to remove the bulk of the material from the edge of the blade. This saves work after heat treat and establishes a center line for the edge.

HARDENING THE STEEL

At this stage, the steel is normalized in preparation for heat treat. Normalizing refines the "grain structure" of the steel and prepares it for hardening by essentially making it as fine as possible.

Hardening changes the state of the steel into a new, very hard material called Martensite. This is the basis of a sharp knife.

 

To achieve this, the steel is heated slowly to 1500° whereby the carbon within the steel goes into solution. At this moment the knife is quenched, basically "freezing" the carbon in its new arrangement. The knife is now extremely hard, but is not yet functional.

A very hard knife will hold a great edge, but will be quite brittle and prone to chipping. To help make the knife tougher without sacrificing too much hardness, the knife is tempered a number of times at around 400° to increase the ductility of the steel. 

Tempering Post heat treat

Finish Grinding

One of the final steps to create a blade is finish grinding. This is one of the most critical steps where hardened steel is ground away and the knife is thinned out to create what is called the "geometry" of the edge. The thinner a knife is, the less material you are trying to push out the the way as the edge cuts into food. 

The grinding is done carefully with frequent water cooling to prevent the blade from overheating which would ruin the molecular structure of the martensite that has been created. 

When the blade is finished, all that's left is to build a handle to make the knife functional. All sorts of different materials can be used for this, I personally prefer stabilized woods or composite materials like Micarta or Carbon Fiber to build up a sandwich bonded with epoxy and mechanically secured with bolts. Once the glue is cured, the handle is shaped, sanded and finished with a wax.

HANDLE CONSTRUCTION

For any cutting tool, sharpening needs to be done regularly. For the initial sharpening on a freshly minted knife, the bevel on the edge must be "set" which means removing a very small amount of material from the edge at an angle prescribed by the work intended to taper the edge of the knife basically to infinity. 

This creates a small secondary bevel on the knife which is where all future sharpening work is typically done. 

SHARPENING