What if the tungsten steel blade is not sharp?

This can be externally ground, so long as there is a suitable grinding wheel and tool grinder, it is very convenient.

If you want to trim the edge manually without machine tools and grinding wheels, you can consider grinding the edge on the flat plate with diamond grinding fluid. But it takes a lot of time and skill, and the average master can't cope with it. Let's go outside and grind it. It's easy to grind, and it can reach the mirror surface, and it's extremely sharp.