What You Need to Know
One of the quickest ways to bring frustration to your craft table is to try to use dull tools. Instead of cutting, they tear. Instead of being easy on your hands, you push or squeeze harder and fatigue sets in. It is more difficult to move though the material, and it is more dangerous as you apply pressure, and the tool slips. It is expensive to keep on replacing tools that are too dull to use.
Sharpening your tools is a necessary skill to learn. Not only do you save money by not replacing tools, but a sharp tool makes crafting fun.
I can teach you how. It will take 3 posts to cover what you need to know.
The Fundamental Concepts
In order to make future posts easier to understand, let’s cover off a few principles of what makes a tool sharp, and what makes them dull. We’ll use a knife as our example.
What Makes Them Sharp
The sharp edge of a knife has 3 characteristics that you need to consider when sharpening.
- The angle of the edge.
- The sharpness of the edge.
- The smoothness of the edge.
The sharpest edge is one that is paper-thin. Think of a scalpel or razor blade. It is thin. But a thin edge is not very strong. it gets dull after just a few uses.
The strongest edge is one with a thick edge. Think a splitting maul or an axe. But, a thick edge is not very sharp, nor is is easy to use.
The compromise is an edge that is thin as it can be and still maintain strength.
An edge that is 20 to 30 degrees total is an edge that is sharp, and one that is strong.
You will try to keep the angle of your tools’ edges within this range.
The sharp edge is one where the sides of the edge meet in a pointy edge. An edge gets dull when the edge begins to get rounded over, Instead of slicing because of the pointy or sharp edge, it has to push its way through your material.
When sharpening your tools, the goal is to have the edge as pointy as possible.
Finally, the sharpest edge is one where the metal is shiny smooth. A polished edge is the sharpest one.
You will use some advanced supplies to polish your edges.
The Sharpening Tools
I like to use at least 3 steps to keep my tools, chisels, and knives sharp.
To make the gross edge sharp, I use a coarse sharpening stone. The abrasive is large, It removes plenty of material fast so I can rebuild the major angle of the edge, and to cause the edge to be sharp at the edge. But, though it has the right angle, and the edge is pointy, it is very rough and needs to be smoothed some more.
Once my edge has been rebuilt. I move to a fine stone to wear down the roughness to make the edges smooth. Often, this is enough sharpness for the task at hand, and I’ll proceed to cutting.
The last step is to charge a leather strop with some polishing compound and polish all the surfaces to a mirror finish. Boy, are my edges sharp!
My tools, then, are a multiple-grit stone, and a leather strop. I also have various files, diamond stones, and some motorized grinders. Not all are required, but I end up using all of them at one time or another.
The process is to use various grits of sharpener to grind away metal at each stage. The grits start coarse then moving to finer grits.
The sharpening stones have hard abrasives. The abrasives are pointy and sharp on their own, and are harder than steel. As you move the blade across the abrasives, they scratch away small particles of of the steel. Each pass removes more steel until it reaches the desired sharpness.
But, coarse abrasives leave the edge rough, not smooth. The next step is to use a finer abrasive to grind away the roughness to make it smoother and smoother.
Finally, we use an abrasive that is so tiny that the steel ends up being polished.
I set my blade at the correct angle for the blade, matching the existing one as close as I can. Then, I draw the blade across the stone away from the edge making the entire edge have contact with the stone.
After 8 or 10 passes, I test for progress by testing for a wire-edge on the opposite side of the blade. This is an artifact of the grinding action of the abrasive and me dragging the blade away from the edge. I test by stroking across the flat part of the blade towards the edge. If it’s there, you will know because it will drag on your fingers.
Remember that a dull edge has been rounded over. As long as the edge is round, there will not be a wire edge to feel. When the edge has been straightened, and is no longer round, you will feel the wire edge. The goal is to create this wire edge along the entire length of the edge.
With a full wire edge on the first side, I turn the blade over and use the same number of strokes on the other side until I have another wire edge. That’s enough, and time to go to the next finer stone.
Sometimes, I use a 3-grit stone. If so, I do the same on the medium stone.
For the finest stone, I reverse direction and try to slice off a piece of the stone. I can’t of course, but 8 or 10 slices on each side are enough to make the edge pretty smooth.
Finally, to polish the edge to a mirror finish, I have a leather strop with polishing compound spread on it. I revert back to my original stroke and draw the blade away from the edge.
How to Test Sharpness
A test of the entire edge is to try to slice off a strip of paper from a newspaper or copy paper. A perfectly sharp edge will slice right through the paper without catching, If it catches or tears, your edge still needs work.
Danger! The following methods can result in blood!
The quickest way to test for sharpness is to touch it. I lightly drag my thumb print across the edge at 90-degrees to the edge. As long as it is across, not with the edge, there is small chance of cutting yourself. A sharp edge catches my thumb print. A dull one will feel smooth.
Another way is to gently slide the edge across a fingernail like you are trying slice it. A dull edge will slide without catching. A sharp edge will catch and get stopped on the nail.
My ultimate test is to try to shave with a sharpened blade. Not my face (although I can), but a patch on my arm.
Yes, I can shave with my blades once I’m done. That is the ideal sharpness for any tool.
With these principles and an overview of the process, it might be enough for you to make your tools sharp.
But, next time, I will detail how to sharpen any knife or blade, including Xacto-type blades.
In Part 3, I will teach you how to sharpen any kind of scissors.