During this time I also read many web forums on sharpening - forums in which strongly held opinions are presented.
To broaden my understanding I have read a number of books on Metallurgy and Metallography. Metallurgy is the study of the production of steel. Metallography is the the study of the internal structure of metals.
All this to understand how best to sharpen tools.
GoalFirst, though, what is our goal when we sharpen a tool? It is not just a tool with the finest possible included angle at the edge. We could prepare a plane iron with a 15 degree included angle that would cut very well but would require resharpening after just a few feet of planing.
Sharpness in tools means the right balance of edge sharpness and edge durability. We want to be able to plane several hundred feet between sharpenings.
Finding the right included angle is a matter of experimentation. You can begin with a standard angle and experiment with larger and smaller angles and see which angle works best for the wood you are using and your style of working.
Sharpening SystemI present in these pages a sharpening system - a combination of jigs, abrasives, angles - that produces reliable angles and steel at the edge in good condition. The combination produces a durable edge every time.
Other sharpening systems - different combinations of jigs, abrasives, angles - will either not produce a reliable edge angle, or will produce a less durable edge, but most likely a combination of both.
JigEveryone uses a jig. Some prefer to use the jig that is the human body. They have devised ways of locking their wrists and hands, rocking from heel to toe, etc. Others use the hollow grind produced by a grinding wheel.
So, the question is not whether you use a jig. You do. How good is your jig?
A jig that is unable to meet both of these criteria will produce inferior tool edges.
Angles and MicrobevelsA microbevel is produced when you increase the the honing angle by one or two degrees. When you do this, initially the tool is resting just on the edge. As you hone, a new bevel forms beginning at the edge and widening with honing. Even with very fine abrasives you are able to quickly form a microbevel that removes a depth of metal at the edge. Sketchup model of microbevels below.
We will see when we discuss steel condition at the edge that fine abrasives cause less damage to the crystal structure of the steel. Very fine abrasives are able to remove steel with almost no damage to the steel at the edge. The result is a tool that is as durable as possible given the steel in the tool.
AbrasivesIn order for microbevels to work, you must proceed through a series of abrasives. The system described in these pages uses 15, 5 and 0.5 micron 3M abrasives. The 15 micron produces sub-surface fracturing - a finding from the engineering field called Metallography. The 5 micron removes that fracturing but produces some shallower fracturing. The 0.5 micron removes that fracturing while producing almost no fracturing itself.
The finest abrasives, those that produce almost no fracturing beneath the scratches they produce, remove metal very slowly. Much too slowly to be used on an entire bevel. They can only realistically be used if you use microbevels.
Many people try to solve this problem of slow metal removal by combining grits. You will see elsewhere in these pages the actual grit combination in an abrasive labelled as 0.5 micron. In fact, it is mostly particles over 45 microns. Such an abrasive leaves subsurface damage associated with the 45 micron grits. It is completely inappropriate as a final abrasive. People who use it will find their tools dull very quickly.
End of the beginningTo get the right edge shape and the right steel condition at the edge, is the ultimate goal of every sharpener. Follow the system described in these pages and you will reach that goal quickly every time.
The Sketchup model of a sharp edge (on the left) and a worn edge (red, on the right) clearly shows the challenge a sharpener faces. Both surfaces of the tool have been modified during use. Sharpening using a jig like mine will quickly return the tool to the sharp state. Other methods probably won't. For example, any freehand method will instead take you somewhere between sharp and dull (closer to dull). Any jig that does not do back bevels will get you somewhere between sharp and dull.
You can use a dull tool. You did use it while getting it dull in the first place. Why work with dull tools all the time, when sharpening correctly is so easy. Watch this video of me using my honing system to see how quick and easy it is.
Check out the introduction to Sketchup models that shows honed microbevels and wear bevels.Sharpening
Examination of sharpened blades over 8 years has convinced me that a combination of 3M Micro-abrasives on glass and a simple shop-made jig produces the best quality edges. No other sharpening system I am aware of can produce edges this good. You will see the photomicrographs in these pages that prove that this combination works. What other sharpening system shows you photomicrographs of their honed edges?
People regularly send me pictures of jigs they have built. If you build some jigs, send some pictures along. Send along your best picture of a shaving as well.Testing
You have all read the claims by tool makers about how their blades last 5 times as long as ... blah, blah, blah. Have you even been shown their tests?
Tool testing has three phases: tool preparation, the test, and test evaluation.
You decide which blades are the most durable. (None of that "our blades lasted 5 times longer" stuff.)The QX3.
A description of the Intel QX3 microscope.
Some people might be interested in the microscope itself. This section also contains an introduction to the images of plane blades, knives, razor blades.My other pages.
In addition to plane blades, I also sharpen saws and chisels, and travel.Links.
Other people who are sharpening and testing plane irons.Updates.
Check the update list here, or join my Google group to read about updates to this site and ask questions about sharpening and honing.
You can email me from this page.Translation.
Google brings people from all over the world to these pages. It probably brought you! If you can translate a page or two to some other language please email me.
If you have any ideas on how to manage translations and versions of web pages, that would be helpful as well.
Google will translate these web pages into your language. If you find that some words do not translate well and have better translations, let me know.