OK, a couple of times I have said this would get done. Here it is in all of its rambling words and pictures.
Sharpening is one of those things that gives rise to many opinions and heartfelt debate over preferred methods. There is also a lot of discussion of cambering blades.
My experience is limited in this area. I make no claim to be an expert. In my opinion, if your sharpening is working for you, then you must be doing something right. In the last few years my sharpening has become much better. Hopefully it will continue to improve over the coming years.
This post is only my opinion on another method for cambering a plane blade. Most of the time my blades are not purposely cambered. If my lumber came with a rough surface, then a blade might be cambered to use like a scrub plane. If my work was in more expensive woods and making fine high priced furniture, then my blades might get cambered for the final smoothing.
Please offer your comments, suggestions, experiences and ideas in the spirit of "this is what works in my shop." If you have tried these or different methods and they have had problems or successes that you can share, it will make it more interesting and add value for all who read this thread.
Before anything else, the blade must be sharp. The definition of sharpness can be quantified, but the actual physical being of sharpness seems to be a moving target as we become more skilled at sharpening.
Testing for sharpness is also an area of wide debate.
Some will claim they can tell if a blade is sharp enough by testing against their thumbnail.
Thumbnail Sharpness Test.jpg
They are correct. It does take some time to learn this method of sharpness testing. It also is not a good one to use if you have a propensity to keep the free edge of your nails trimmed.
In my experience the sharpness can be determined by the feel of the edge against the nail and the angle at which it must be held to "stick." It is also possible to get the edge to "stick" without being fully sharp. This is where experience comes in with every test mentioned here.
Another method that is often mentioned is the push through paper test. This is perhaps the safest way to check for sharpness. As long as fingers and other flesh are kept out of the path of the blade there will likely be no mishaps.
Paper Sharpness Test.jpg
The less stiffness in the paper, the sharper the blade needs to be. Also, a slicing motion is kind of like cheating. To test sharpness it must be a straight push into the edge of the paper.
I do not use this test, but it is a good and safe way to test a blade's edge.
I didn't take any pictures of the hair shaving method of testing the edge of a blade. Though this is my most used way to test a blade, it can be dangerous. It may be that when young, it was my habit of not shaving for a few years at a time that lead me to use a straight razor. In those days we didn't have the multi bladed razors that are common today. The confidence of dragging one of those across my neck may be why pushing a chisel or plane blade across my arm doesn't seem out of the norm for me.
Like the paper or thumbnail test, there are different levels of sharpness that can be detected by the arm hair test. A really sharp blade will not leave any hair in its path and you will not feel hair being cut.
The end grain test also was not photographed. A sharp blade should be able to take a very fine shaving from the end grain of pine or other soft wood. In a plane, if it takes a fine shaving, it is probably sharp. Otherwise, what one often gets is dust or a need to take a thick shaving.
Why camber a blade?
This is an often asked question. For a scrub plane it is obvious, it is easier to get to the wanted thickness and remove saw marks planing diagonally or across the grain with a deep cut. A cambered blade helps with hogging off wood in these situations.
Some like a slight camber across the full width of their jointer planes. This is something for someone who uses such to add if they choose. It is something of which the theory is understandable and has its appeal. The theory of time travel is also appealing, it is just that neither have happened for me as of yet.
For many people a slight camber at the edge of a smoother plane is helpful in eliminating "tracks" sometimes left by the corner of a plane's blade.
Methods to camber a blade are likely as plentiful as the ways to sharpen a blade if not more so.
My thoughts on this come from my experience while flattening the backs of old blades that would come up great in the center but not the edges. Maybe that was because craftsmen of years gone by also relieved the backs of the blade at the edges.
This is what the shaving looked like from a freshly sharpened blade mounted in a #5 type 17 before being "cambered."
Full Width Shaving.jpg
Please note this shaving was taken on a scrap of wood used for testing gouges and knife blades. The area of the shaving on the ruler was not affected by previous tests. The areas where the shaving is broken are where there were depressions in the surface from previous tests.
Here a small stone is used to emphasize this being done in just a corner of the blade. It only takes a few strokes. It will even go faster if done on a coarser stone.
Back Side Rub.jpg
One "camber" was done on the back of the blade and a second was done on the bevel side for comparison purposes.
Bevel Side Rub.jpg
The honing of the camber is done at an angle. This will tend to feather the edge so the camber will be most at the edge and diminish towards the center of the blade. In total it was less than 10 short strokes on either side of the blade. YMMV
The blade was reinserted into the plane and adjusted to take a similar cut.
"Cambered" Blade Shaving.jpg
The shaving is not the full 2" at about the same shaving thickness. Running one's fingers over the planed surface does reveal that the edge of the blade being cambered does make a difference in the surface. YMMV
One of my bevel up block planes has a blade that has the underside of the blade corners relieved. It is similar in action.
In my opinion, if one wanted to "camber" the blade on a bevel up plane, a slight honing on the corners of the "blade's back" might be an attractive alternative.
jtk
Reply With Quote
Originally Posted by john brenton
