Wood Carving: How To Sharpen Straight Chisels
If you're going to be a true wood carver, you really should learn how to sharpen your own tools. And straight chisels are the easiest carving tools to sharpen. Once you know how to do it correctly, you could sharpen any other straight-edged tool in your collection.
If you're just starting out as a wood carver, you'll quickly discover how wood chisels are used all the time. There are many kinds, many sizes. They'll need periodic sharpening and it's good to be able to do them yourself. It isn't very fitting to have to bring your tools to a professional sharpener whenever they become dull. You lose money, you lose time. And best of all, straight chisels are the easiest wood carving tools to sharpen.
Straight chisels can be sharpened in two steps. The first is to get the tool's edge to sharpness, and the second is to strop that edge to silky smoothness.
æ Straight Chisel Sharpening. This is sharpening for straight square chisels and it's very simple. Start with a coarse grade sharpening (honing or whetting) stone. Make the shaft vertical with the edge touching the stone. Slowly lower the end facing up until the edge's surface touches the wood. Stop right there. With the beveled face flush on the stone, you have achieved the correct sharpening angle.
While holding the chisel's beveled face flush against the stone, place your index finger on the top of the beveled surface for better control. Pull the stone towards you, away from the edge. Do this 10-20 times and then check for the burr. A burr is a feather-like sliver of wire that will come off the chisel's edge when you have achieved absolute sharpness. You slide your finger across the edge (never lengthwise!) and a burr will feel like sand or grit on your edge. If there isn't a burr, do another set of strokes until you've correctly raised it. If the tool has a second bevel, sharpen it as you have just done with the first bevel. Sharpen until you've correctly raised the burr.
After sharpness has been achieved with a coarse stone, move to a fine grade stone. You can do this with just one fine grade stone or with a succession of increasingly fine grade stones. Perform the sharpening strokes in the same way until you get a burr. If you've got a second bevel, do the same until a burr is raised. Be very sure that you've raised a burr along the entire length of the chisel's edge, and on both sides. If you won't make sure, just stop what you're doing and go watch television. I'm not kidding. If you're going to sharpen, do it well or not at all. It will affect how well you're able to carve. (If that doesn't matter to you, really, then what are you doing?)
There are a couple of different stroke techniques that are commonly used when sharpening straight chisels. With your index finger on the top of the beveled surface as you grip the shaft, place the fingers of your other hand on top of the first. Instead of pulling the tool towards you, you run it in circles. If not that, you can also push the tool sideways in one direction and then sideways in the other. There is no one specific method. Experiment and see which technique is best for you. I like the stroke that pulls away from the edge best. It's the simplest way to raise a burr and then detect it.
æ Skewed Chisel Sharpening. Skewed chisels are just a bit different from straight chisels. A skewed chisel's edge is at a slanted angle, a skewed angle, and joins the side of the chisel head at an acute angle of less than 90 degrees.
Sharpening a skewed chisel is done in just the same way as sharpening a straight chisel. There is only one difference. The skewed edge needs to be made parallel to the forward edge of the sharpening stone. Or the edge can be made perpendicular to the side edge of the sharpening stone. Either way works fine. Just be consistent if there is a second bevel.
æ Chisel Stropping. Your well-sharpened chisel now has burrs all along its edge. Well done. Stropping will remove those burrs and all other micro-bits still clinging.
You've got a couple of choices when it comes to stropping. First choice: You can use a free strap of leather to strop your edge in one direction and then the other. Lay the beveled face of your chisel's edge flat on the strap and pull away from the edge, parallel to the length-wise surface of the strap. Near the end of the strap, lift the chisel and turn it over. Place the opposite face of the chisel's edge flat on the strap. Pull in the opposite direction, away from the edge and parallel to the strap surface. Back and forth and back and forth until your edge is silky smooth.
The second choice for stropping your chisel edge is to use a stropping board, also referred to as a honing board. This could be in the form of a flat rectangular board, a paddle, a wooden bench or it could be one you make yourself. The technique for using a stropping board is just the same as the technique used on a free leather strap.
Leather strops and stropping boards are usually combined with a polishing compound. It facilitates the stropping process and makes carving much easier. It may be in the form of a liquid, a paste, powder or even a solid block that fits in the palm of your hand.
Stropping is a very important step in sharpening and shouldn't be dismissed. Think of it as you using a chisel with a dirty edge. It surely doesn't perform as well as a clean edge. And because it's dirty, using it will cause you to have to sharpen it much quicker than you usually would. So strop, and strop well. Your carving will be better for it.
Beginners need to be very careful when stropping. As novices in this art, the edge is often rounded instead of being polished smooth. That's because the edge isn't truly flat during the stropping process. A secondary bevel will be produced that thickens with each sharpening. Eventually, the only way to save the edge is to remake it. That would be a great loss in time and effort. Pay close attention.
When you've trained those hands to do a good job, you'll be able to sharpen any straight chisel, any skewed chisel in your tool collection. That's a lot you already know about sharpening carving tools. Keep it up. Just be so careful and watch out for secondary bevels.
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ABOUT THE AUTHOR
Len Q. is a master blade sharpener and an adventurer who strives to protect the natural world. If you would like to find out about - Knife Sharpening: How to Sharpen Knives, Maintain and Store Them - Sharpening Other Edges (e.g. Lawn Mower Blades, Chain Saws, Gardening Tools, Axes) Find it here at http://www.MakeKnivesSharp.com .