Does anyone know if there is any type of chart, or rule of thumb, that shows what is the best angle to grind various types of chisels and plane irons.
Over the years, I’ve accumulated a wide variety of chisels, from bench to mortising chisels, and have always ground them to 25 degrees. Some people say the grind depends on the type of chisel. Is this true?
Planes are another story. I have over a dozen planes, and I’m never really sure what they are supposed to be ground to. Also which plane irons benefit from a camber, vs. being ground straight. Which planes are supposed to be bevel down vs. bevel up.
What about irons on old wooden planes. What angle should they be ground to? Should they be hollow ground, if possible, or flat ground. For ex. I have a smoothing plane, a plow plane w/6 of the 8 irons, and a jointer. Then there’s the molders. I have 4 of those, and I usually try to simply follow the same angle that was there already, but that’s not easy either. Can someone give me advise? Thanks!
Replies
While there are some exceptions, carving tools as an example, most of what I do is grind at 25º and hone at about 30º. The easiest way to set a grinder's tool rest is to cut a small piece of wood the same thickness as the tool and cut the 25º on the end. Because you're grinding on the tangent of the grinding wheel, the thickness of the tool will make a big difference. I also cut a 30º bevel on the other end of a grinding template, usually a piece of wood about 3/4" X 6" X the tool thickness, for use during honing. I can check my hold on tools for honing with this and it can help develop the muscle memory to keep your tools pretty close to 30º on the stones. We're not triying to land a rocket on the moon here and a degree or two doesn't make a lot of difference.
Further to Larry's advice, you can use the following jig to grind your blades to the desired angle on the primary bevel.
http://www.inthewoodshop.com/WoodworkTechniques/AngleSettingJigForDryGrinder.html
Regards from Perth
Derek
chisels not to grind
I would not use a grinding wheel to grind the primary bevel on a mortise chisel or a japanese chisel. These chisels benefit from a flat bevel due to the abuse they take when chopping. I would be hesitant to hollow grind any chisel that you primarily strike with a mallet, just my opinion. Also important to consider is the type of steel. Some steel can hold a low angle and some can't. All things to consider. I hollow grind my paring chisels and flat hone all the others.
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