03-29-2010 12:28 PM
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!
03-29-2010 01:40 PM
I do not know of any "chart". Sorry. But I do have a few answers based on experience. 25 degrees is a good start point for any plane/chisel. Changing the angle does a few things to the blade. A steeper angle will cut a bit better, but also will make a plane harder to push, in general. Also the edge will not last as long. So for say a mortise chisel, most practice would be no angle greater than 25-27, or so. As far as camber, in my opinion, all should have some sort of camber. This eliminates "plane" tracks. How much camber is up to you. The heavier the shaving, the more camber. The finer the shaving, less camber. Our question about hollow grind, well that really depends on how you sharpen. Most all blades start as hollow. Then get flat, if you use a honing guide. But if you just free sharpen, no guide, then the hollow grind makes this more consistent. Different angles help with different woods/grains also. Try changing them by 4-6 degrees at a time and see what happens. Hope this helps.
03-29-2010 01:43 PM
Well... what you're really asking about is about like asking if chocolate is better than vanilla. There really is no right or wrong answer to many of these questions. It really depends on the type of work that you want the chisles and plane irons to perform.
As a general rule of thumb I'll grind my irons and smaller chisles to a 25° angle. My larger chisles (an inch wide or better) will usually be ground to a 30° angle. But that's just in context with the work that I do. Others may have other methods, and that's perfectly normal.
As for bedding the irons, you have some choices. The effective cutting angle of the tip of the iron at the wood is the mathmatical sum of the bed angle + the bevel angle. High cutting angles (50° or more according to how I look at these things...) can be very advantageous, albeit: hard to push through the wood, if you're tackling squrrely grained wood. And of course, low angle planes are great at things like paring end grain. I've got a collection of a few dozen planes, some store bought and some that I've made myself. I go from about 40° or so in effective cutting angle up to a whopping 75° on one plane (45° bed angle + 30° bevel angle) for when I'm working with figured wood. it almost acts as a scraper.
As for cambers... that's again a personal choice thing. If you've got a big two-handed model that'll be used for scrubbing down irregular surfaces, then a camber can be your friend. Not necessary, but occasionally advantageous. Especially if you're going to leave the surface as a hand planed look with little other prep. The camber eliminates corner dig marks.
Anyway - just some of my mileage. Others are sure to chime in with their mileage.
03-29-2010 01:54 PM
Usually the angle that I grind depends on the wood that I'm planing or chiseling. That being said, I generally grind a bit steeper angle on a mortising chisel and I generally have less of an angle on paring chisels.
I "grind" a slight camber on most of my plane blades (but not my rabbet planes or plaw planes).
I would recommend two books.
"The Complete Guide to Sharpening" by Leonard Lee (founder of Lee Valley)
"The Handplane Book" by Garrett Hack