DO BEVEL ANGLES MATTER?
The other day, I did some searching online to find out what bevel angles people were recommending for chisels and hand planes. Now I know how Alice felt when she fell down that rabbit hole. People get really worked up about their bevels. You can be taking your life in your hands if you suggest the wrong angle on the wrong forum, let me tell you. Some people insist on a precise angle for pine, a different one for oak, another altogether for cherry, one angle for long grain, another for end grain. If you work with a lot of different woods, you'd need a hundred different planes or chisels set up with different bevels, or else you'd be regrinding your tools to nubs with the constant changes.
I'm here to tell you it doesn't matter. Well, it does matter a little, but not as much as people seem to think. Let's discuss how your bevel angle affects the way a hand plane cuts, then we'll discuss chisels. In the end, I think you'll agree that there are far more important things in life to worry about than bevel angles.
Hand Planes:
Most hand planes are properly assembled with the iron's bevel facing downward. As you push the plane forward, the iron's edge digs beneath the surface of the wood. The angle at which the top surface of the iron is set is what matters, as that's what digs into the wood fibers. That's already set at 45 degrees by the part of the plane that holds the iron, called the frog. The bevel angle you grind on the iron itself won't change that. All the bevel does is provide some clearance beneath the plane for the wood fibers.
If you grind your bevel to 45 degrees, that, added to the 45-degree frog angle, would equal 90, putting the surface of the bevel parallel to the wood surface. That would prevent the iron from digging into the fibers, and your plane wouldn't work. So, we grind the bevel shallower to provide some relief so the edge can dig in. A lot of people go to great pains to make that bevel 30 degrees. That gives you 15 degrees of clearance, way more than you need. Frankly, four or five degrees is enough to overcome any compression in the wood fibers and still keep the heel of the bevel above the wood.
That doesn't mean you should grind 40-degree bevels on all your irons. It just means you don't have to worry so much about the exact angle of the bevel on a bench plane. Anywhere between 25 and 40 degrees will give you the clearance you need. 30 degrees is common because it produces a durable edge, but 35 or 38.5 degrees would be just as durable. It would still give you the clearance you need beneath the plane, and it's not going to change the way the plane cuts at all, because that's set in stone by the angle of the frog.
This is good news for people who want to hone their bevels without a jig. Don't worry about holding it to a specific angle. Just concentrate on keeping whatever angle is comfortable for you consistent.
If you want to change the way the plane actually cuts, you have to swap out the frog, which few people do, or use a bevel-up plane. Since the bevel is on top, the angle at which you grind it will make a difference. Now your plane is working like a chisel, which is almost always used bevel up, and in those cases, angles can make a difference.
Chisels:
Here's where bevel angles get a little confusing. Remember, I said the angle of the top of the tool is the critical one, and when your bevel is facing up, it becomes the surface doing the cutting. Changing that bevel angle has the same effect as tilting the tool up or down—it will change how the fibers are cut.
Let's illustrate this with a lesson I learned from hand tool expert Ron Herman some time back. A soft wood, like poplar, has very flexible fibers. With a paring chisel ground to about 15 degrees, those fibers will easily lift up and ride over a shallow bevel angle. Change to a steep bevel angle, such as 35 degrees, and the fibers will force the chisel deeper into the wood, making it more difficult to cut and potentially tearing a chunk out.
But the opposite will happen with a harder wood like oak. Those fibers are very hard and do not flex well. They will quickly wedge on top of a shallow bevel and make it very hard to cut. But hardwood fibers are also more brittle, so if you increase the bevel angle to 30 or 35 degrees, the fibers will bend upward so much that they will break and roll back, allowing the edge to cut much more easily.
That's just one way a bevel's angle can affect the way a tool cuts. Another has to do with edge retention. A very shallow bevel has little steel near the edge. It's going to wear away more quickly than the thicker steel of a steeper bevel, especially if you are using it for harder woods.
Are you sensing a trend here? Shallower bevel angles work well for softwood because the fibers are more flexible and don't wear on the steel as much. Steeper bevels work well for harder woods because they better roll back the fibers and stand up to greater abuse.
Bottom Line:
So, does this mean you need to constantly match your bevel angle to the tool you're using and the material you're working with? No. If you're the average weekend woodworker, you probably only use your chisels for the odd paring jobs. You aren't spending an hour fine-tuning hand-cut joinery. You're trimming a dowel flush with a surface to plug a screw hole or cleaning up a little tearout along the shoulder of a dado you just cut with your table saw. For those small cuts, it doesn't matter a great deal what type of wood it is. Your chisel just has to be sharp.
So, I recommend around 30 to 35 degrees. That's a durable edge, and it will work perfectly fine for small chisel tasks. For hand planes, we already discussed how it will make little difference what angle your standard bench plane is ground to as long as you have clearance for the fibers beneath. So stick to the same 30 to 35 degrees there as well.
If you're a hand tool user who does a lot of planing and chisel work, then you may want to have some variety in your bevel angles. But you don't have to get carried away. I recommend 20 degrees for fine paring chisels that won't be struck by a mallet. That will work for delicate cuts in all but really hard woods. For standard bench chisels, go with 25 degrees for softwoods, 30 degrees for hardwoods, and for really stubborn woods, you might add a 35-degree micro bevel along the cutting edge.
Does this mean you need three or four sets of chisels? Nope. Again, most hobbyist woodworkers can get by with one chisel honed to about 30 degrees or so. Many hand tool lovers can get by with one 1/2" paring chisel at 20 degrees, a couple of softwood chisels at 20 degrees, and a couple of hardwood chisels at 30 or 35 degrees. For standard bench planes, you still only need one bevel angle of somewhere between 30 and 40 degrees, unless you want to use bevel-up planes, in which case you revert back to the chisel rules.
Some hand tool pros insist on many different bevel angles. Others, like Chris Schwarz, grind everything to 35 degrees and refuse to get caught up in the hype. What you do is up to you, but I hope the lessons in this video help you decide.
For more great tips, tricks, and tutorials designed to make you a better woodworker, check out Stumpy Nubs Woodworking Journal. You can read and subscribe for free at Stumpynubs.com. Happy honing!
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