Sharpening chisels


This article focuses on sharpening chisels, but the information applies to other flat edge tools as well.

If you want to enjoy using hand tools you'll need to learn how to sharpen them. A properly tuned and sharpened tool can be a joy to use. A dull one is both frustrating and dangerous. I encourage you to learn to sharpen your tools.

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Sharpening isn't difficult but it takes practice. You will probably dull a few tools while learning to sharpen them, but that won't hurt anything. Just think of it as giving yourself an extra practice session.

Knowing the correct angle for the bevel is important. For example, on chisels the range is generally 15-35 degrees, depending on the tool and the wood (lower angle for paring, higher for chopping). Bench planes are often around 25 degrees.

Many factors go into getting the right angle. In the beginning, keep to the original angle of the blade you are working on. You can experiment with different angles as you improve your technique.

steel and tools

A quick word about steel. The Rockwell C Scale is the industry standard for measuring the hardness of tool steel. Hard steel is good, however there is a trade off. The harder the steel, the more brittle it is. So a really hard steel, such as on a carbide saw blade, will cut nicely, but will also chip easily.

Fine tools will find a good balance being as strong as possible for the use. Unfortunately, there isn't any way to tell the quality of the steel until you use it and see how long it holds an edge and how easily it chips.

Fascinating, I'm sure, but none of this tells you how to actually sharpen a chisel or any other tool.

how sharp is sharp?

The first thing you need to know is how sharp is sharp enough. That will depend on the tool and the purpose. If you sharpen an ax as you would a hand plane you'll simply break the edge on the first swing, so no need to bother.

On the other hand, if you want a shaving thin enough to see through you'll need as sharp an edge as you can get. Once you've used a tool that has been properly sharpened you'll learn how to gauge what you need. Until then, keep practicing. When you hit the sweet spot you'll know it.

chisel sharpening systems

To begin sharpening chisels or any other tool you'll need a space to lay out your tools, keeping in mind that it is a messy process.

There are a lot of different systems for sharpening and everyone has their favorite. In another article I'll cover some of the machines that can make sharpening easier.

For now, I'll talk about sharpening chisels with water stones, oil stones or sandpaper. There are advantages and drawbacks to each of the three. Water stones cut quickly but are soft and need to be flattened often (more on that later).

Oil stones go much longer before you need to flatten them, but they are messy and cut more slowly. (The harder the stone the slower it will cut. The soft stones crumble more easily so they are constantly exposing sharp new particles.)

Sandpaper can be tossed when the grit is worn, but I don't care for all the waste. So, for me, it's water stones, but the process is basically the same for oil stones and sandpaper.

begin sharpening chisels by grinding

sharpening chisels
sharpening chisels

If the tool is really dull or has dings in it I'll take it to the grinder. With the grinder off, I set the tool rest to the proper angle (see above). You can experiment to find the angles you like. Once I have it right I'll begin grinding.

The trick to grinding is to move the blade slowly and evenly across the width of the wheel. If the tool starts to get hot take it off the wheel until it cools then begin again. If the steel turns blue you've ruined the temper (strength of the steel) and the blue area will chip easily. Don't worry, you haven't destroyed the tool, but you will have to grind beyond the blue.

Your goal is to grind an even bevel that comes to such a fine point you can't see it when you eyeball down the blade. To visualize what I'm talking about imagine you took the end of the chisel and pushed it into the wheel. You would soon flatten the point (lower chisel bin drawing).

What you want instead, is the sharpest point possible (upper chisel). If you can see any edge when you sight down the blade you need to keep grinding.

sharpening chisels

Once you have a nice even bevel that ends at a point too sharp to see, it's time to move to the stones to hone your tools.

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