Brent's Sharpening Pages

	Brent's Sharpening Pages
	Finest abrasives.
	Microbevels front and back.
	Use a jig.

	Copyright © 2002-15, Brent Beach

The 80+ or so pages that make up this web site were written over a period of 10 years. During that time I used an Intel QX3 microscope to take photomicrographs of both faces of plane blades, right at the edge, during sharpening and during use. While sold as a toy, the QX3 has good enough optical resolution for me to distinguish:

freshly sharpened edges from dull edges,
the scratches left by coarse abrasives from those left by fine abrasives,
the changes that occur on both faces of a plane blade during use,
the amount of wear on both faces of a plane blade during a standardized test.

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.

Goal

First, 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 System

I 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.

Jig

Everyone 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?

Does your jig produce reliable angles?
Does you jig allow you to use microbevels on both faces of the tool?

A jig that is unable to meet both of these criteria will produce inferior tool edges.

Angles and Microbevels

A 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.

Abrasives

In 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 deformation - a finding from the engineering field called Metallography. The 5 micron removes that deformation but produces some shallower deformation. The 0.5 micron removes that deformation while producing almost no deformation itself.

The finest abrasives, those that produce almost no deformation 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 beginning

To 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 have sent me pictures of jigs they have built.

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.

Tool preparation
Sharpen the plane blade to the same fine surface on both faces. For most tests I show microphotographs of both the front and back of the blade before the test.
Standardized test
A standardized test (all tests have used wood from the same part of the same tree!) means that the test conditions are the same for all blades.
These are the shavings produced during part of one test.
Test evaluation
The ability to measure plane blade wear to the ten-thousandth of an inch, using the QX3.
In this section, see photomicrograph test results -- before, during and after -- of over 20 commonly used plane blades, both antique and modern.

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.

Need a map?

Try looking around the site map. You can also reach the site map from the little map at the top of each page.