Scraper

What did you shave with, private? A bowl of milk and an angry cat?

Unknown Sergeant

General Guidelines

Primary Bevel

Increase this angle when the tool is being used for scraping harder items (e.g., a gasket scraper).

This edge should be thin, and I recommend it be no larger than ¹/₈” (3mm). If it is, re-grind the secondary bevel as necessary to reduce its size.

Be sure to de-burr this edge after sharpening. Breaking off the burr through use will cause the edge to be jagged.

Secondary Bevel

It is recommended to keep what came on the tool from the manufacturer. An estimate is given here in case the tool needs to be re-ground, as will happen when the primary bevel becomes too large.

Temperature control is critical for high carbon steel. Tempering will be lost in the steel if heated until it is blue (~550°F / 300°C). Cool by dipping as needed in water.

Dr. Larrin Thomas noted in his book, Knife Engineering: Steel, Heat Treating, and Geometry (2025),

The lack of sparks or color changes is no guarantee that the edge was not overheated.

Therefore, sparks are not necessarily a sign that heat has or has not been generated in the steel. Color changes can occur from overheating of steel in grinding, but during grinding, the surface is being removed, and the affected volume can be relatively small. Therefore a color change is not always observed.

Microhardness measurements of edges sharpened with a belt sander show a drop in hardness at edge. This results from “over-tempering” the edge by heating it above its original tempering temperature.

It is also recommended to use a high grit wheel for sharpening carbide as lower grits can cause cracks in the edge leading to it being far more crack-ridden and brittle. (Lower grits can be used for shaping the edge -- see also, Grindstones and Other Sharpening Media - Quick Selection Guide.)