Fair Woodworking

December 15, 2012

Using blade angles to control tearout.

Filed under: Controling tear out,Sharpening,Skill development,Strong opinion warning! — fairwoodworking @ 4:19 pm

There is a lot of talk out there about using higher blade angles to solve tear out issues. It’s mostly applied to bevel up planes, but can also be addressed with back bevels and higher frog angles on bevel down planes.

In the world of golf, advertisers often promote  their new drivers as the solution to your driving woes. “Our drivers larger sweet spot, tighter sweet spot, flexible shaft, stiffer shaft, composite material, lighter weight, ergonomic grip made of mystery plant fibers found only in the amazon, will give you the extra yards you know you can attain.”

Well if your name is Jack Nicklaus their claims may be true, but if you write a blog called Fair Woodworking, you can “Dink Out” with a $50 driver as you can with a thousand dollars worth of carbon fiber.

So is this a fair comparison to the blade angle scenario?

Well it may have its limits…

If we look at the pros and cons of a high angle, I can only see two. One of each, no wait… Three. One pro, and two cons.

Pro #1.  It’s obvious. Higher angles reduce tear out. That is a pretty big pro.

Con #1. Higher angles result in more resistance. The higher the angle, the more work it is to push the plane forward.

Con #2.  It is not often mentioned, but higher angles are harder to sharpen well.

One of the first skills you need to learn with hand tools is sharpening. It’s not that difficult, but there is a learning curve that can stretch over a number of years. Let’s forget about tear out for a bit and just look at planing with the grain, in well behaved wood. What are the signs of a dull blade? The finish is not as nice, the blade does not cut as well, and finally the plane takes more effort to push it through the cut. I’ve heard the question asked a number of times, “how sharp is sharp enough?” I’ve been sharpening for around 6 years now, and I can get a blade pretty darned sharp now. I have to be very careful not to let friends near my edged tools, because even my dull tools are far sharper than they can imagine an edge could be. Even still, what I’m learning is that sharp enough is just a little sharper than I am capable of right now.  The good news is that I know I can still improve more.

I’m not sure I’m doing a great job of making my point, so I’m just going to come out and say it.

In many cases, a really sharp blade set at the traditional 45 degrees will out perform a high angle alternative.

Linking all of this together, many beginner woodworkers struggle with tear out. The reason in many cases is due to limitations in their sharpening ability.  Because their blade is not as sharp as it will be when they get better at sharpening, the plane also requires a lot of force to push. When they hear that a higher blade angle will tame their tear out, they jump at the solution, rather than focus on improving their sharpening skills.

Now you have a novice sharpener with a more difficult to sharpen high angle blade, and a plane that was already difficult to push, made even more difficult to push because of the higher angle. With a sharper standard angle, they wouldn’t have run into tear out so quickly, and it would have been a lot easier to push.

A hundred years ago, when Stanley still made real tools, why didn’t they offer options for higher angels? Other than the lack of modern technology to make fancy new tools, I think it is because their clients could sharpen well enough to get by with standard 45 degrees.

I’m not saying high angles are bad, quite the opposite. In the right case, it gives your plane superpowers. The thing is many difficult woods don’t need a plane with super powers, they just need a plane with a really sharp blade.

I say that because while I don’t use a lot of difficult wood, I do use them occasionally. I do own a few bevel up planes but I don’t have any of them set with cutting angles higher than 45 degrees. All of my final smoothing planes are old Stanley bevel down planes, with really sharp blades, and so far they haven’t let me down.

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1 Comment

  1. Have you heard of the “optimum angle of entry”? Graham Blackburn thinks that a well-tuned plane with a sharp blade bedded at 45 degrees (bevel down) is able to handle any grain. It’s what he called the optimum angle of entry.

    Garrett Hack likes low-angle planes with 25-degree blades and thinks they are capable of handling most grains if set for a fine cut with a tight mouth.

    The takeaway: the most important things in getting a clean cut are a sharp blade set for a fine cut and a tight mouth.

    Chris

    Comment by ChrisHasFlair — December 15, 2012 @ 10:29 pm


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