The Perfect Edge: The Ultimate Guide to Sharpening for Woodworkers

THE PERFECT EDGE

The Ultimate Guide to Sharpening For Woodworkers

RON HOCK

An imprint of Penguin Random House LLC

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Copyright © 2009 by Ron Hock

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Ebook ISBN: 9781440310218

ACQUISITIONS EDITOR: David Thiel ([email protected])

SENIOR EDITOR: Jim Stack ([email protected])

PHOTOGRAPHER: Ron Hock

ILLUSTRATOR: Martha Garstang Hill

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READ THIS IMPORTANT SAFETY NOTICE

To prevent accidents, keep safety in mind while you work. Use the safety guards installed on power equipment – they are for your protection.

When working on power equipment, keep fingers away from saw blades, wear safety goggles to prevent injuries from flying wood chips and sawdust, wear hearing protection and consider installing a dust vacuum to reduce the amount of airborne sawdust in your woodshop.

Don’t wear loose clothing, such as neckties or shirts with loose sleeves, or jewelry, such as rings, necklaces or bracelets, when working on power equipment. Tie back long hair to prevent it from getting caught in your equipment.

People who are sensitive to certain chemicals should check the chemical content of any product before using it.

Due to the variability of local conditions, construction materials, skill levels, etc., neither the author nor Popular Woodworking Books assumes any responsibility for any accidents, injuries, damages or other losses incurred resulting from the material presented in this book.

The authors and editors who compiled this book have tried to make the contents as accurate and correct as possible. Plans, illustrations, photographs and text have been carefully checked. All instructions, plans and projects should be carefully read, studied and understood before beginning construction.

Prices listed for supplies and equipment were current at the time of publication and are subject to change.

METRIC CONVERSION CHART

ABOUT THE AUTHOR

Ron Hock is the owner of Hock Tools, a twenty-five-year-old cottage industry that makes acknowledged superior blades for planes and other woodworking tools. Hock started the business when, as a struggling knife-maker, students at James Krenov’s Fine Woodworking program at The College of the Redwoods in Fort Bragg, California, came to him for plane irons for the wooden planes they were making at the school. He tooled up for plane irons, learned about plane-making and found a niche-market of discerning woodworkers who appreciate a superior tool.

Ron earned a B.A. and M.F.A. in studio art from the University of California at Irvine. In the ensuing quarter-century since making his first plane blades he’s learned about tool steel metallurgy, cutting edge geometry, hand woodworking tools and sharpening. His interest and expertise regarding sharp edges comes from a blade-maker’s perspective and he has given countless lectures about steel, tools and heat-treatment.

DEDICATION

Through his uncompromising craft, teaching and writings James Krenov has inspired and launched the careers of thousands of woodworkers … but maybe only one metalworker.

Thanks, Jim.

ACKNOWLEDGMENTS

A large number of people helped me with this book either directly, by sharing their knowledge and wisdom, or by providing tools, abrasives and technical assistance. I am grateful for their generosity in sharing their expertise. I hope this list is complete yet I doubt it is – I’m sure I have forgotten to mention someone or two; if so, I apologize and thank them, too:

First and foremost is my wife, Linda Rosengarten, for being selflessly supportive and endlessly helpful as my primary editor. Thank you, Sweetie, there is no way I could have done this without you. And my son, Sam Hock, for letting me be a bit less attentive as the fatherly figure that I hope he’s otherwise come to expect.

For hands-on help, advice and lots of tool lending and kibitzing, my immense gratitude to: Kevin Drake of Glen-Drake Toolworks; Paul Reiber, artist and woodcarver; Dan Stalzer, green-wood furniture maker; Joaquin Leyva, woodworker; Earl Latham, tool expert and collector; Joel Moscowitz of Tools for Working Wood; Mike Wenzloff of Wenzloff & Sons Sawmakers, and Christopher Schwarz, editor, Popular Woodworking magazine.

True experts in their fields, generous with their tools and expertise: Wally Wilson of Veritas; Jeff Farris of Tormek USA; Don Naples of Wood Artistry; Kyle Crawford of Work Sharp; Valerie Gleason of Chef’s Choice; Peter Moore of One Way; Linda Jones of Woodsmith; Cindy Martin, Kris Spofford, Dave Long and Trish Dawson of Saint-Gobain Abrasives (Norton); Brian Burns; Stan Watson of DMT; Harrelson Stanley of HMS Enterprises; Rich Bohr of 3M; Bill Kohr of Craftsman Studio; Dave Bennet of Flexcut; Joyce Laituri of Spyderco, and Kent Harpool and Tim Rinehart of Woodcraft Supply.

The professionals, tops in their fields, who helped me with some difficult technical materials: Dr. Abraham Anapolsky, metallurgist; Caroline Schooley, microscopist; Steve Anderson, Sonoma State University SEM technician; Dr. William R. Hoover, metallurgist, LLC; Brian Ross, metallurgist, Latrobe Steel; Hans Nichols, metallurgist, Precision-Marshall Steel; Katherine Cockey, corrosion engineer; Charles Beresford of Cryogenics International; and Jeff Wherry of the Unified Abrasives Manufacturer’s Association.

And, for making this book happen in the first place, and look and read the way it does: Rick Droz, photography advisor; Martha Garstang Hill, creator of the illustrations; Brian Roeth, designer, and David Baker-Thiel, executive editor, Popular Woodworking Books.

Thank you, one and all.

(TABLE OF CONTENTS)

Title Page

INTRODUCTION

1 Why Sharpen?

2 What is Steel?

3 Abrasives

4 How Wood is Cut

5 The Fundamentals

6 Plane Irons

7 Chisels

8 Scrapers

9 Handsaws

10 Carving Tools

11 Turning Tools

12 Axes and Adzes

13 Knives

14 Drill Bits

15 Power Tools

MICROSCOPIC PHOTOS

RESOURCES

SUPPLIERS

(INTRODUCTION)

Give me six hours to chop down a tree and I will spend the first four sharpening the axe.

– ABRAHAM LINCOLN

RELAX. YOU KNOW MORE THAN YOU think you do. Reassuring words for new parents from Dr. Benjamin Spock’s classic Baby and Child Care (that’s Doctor Spock, not Mister Spock, jeesh …) and, amazingly, these classic, reassuring words are applicable to this book, too. A perfect edge is the intersection between two surfaces, one that performs its assigned task the way you want it to. You need only:

1. Determine the correct angle for that intersection.

2. Rub the tool at the appropriate angle on an abrasive surface until that intersection is created.

3. Repeat #2 with successively finer grits until the desired degree of polish is obtained.

That’s it. Really. And you can do it. The perfect edge is all about angles and grits, and what follows here is, I hope, information that will help you make good decisions about them. Clear away all the hype and hoopla, all the myth and magic, all the gear and gadgets and what you have is rather simple: a metal edge and an abrasive means of removing some metal from that edge. Every cutting tool in your shop needs an edge – ground to some angle and honed such that it can perform its intended task.

It’s impossible to describe how to sharpen every tool for every task but it is my sincere hope that, with study and practice, you will understand more and more about what is involved in cutting wood with steel. The more you understand, the easier, less stressful and more intuitive your woodworking will become. Relax.

1 Why Sharpen?

FIRST, A DEFINITION OF WHAT SHARP MEANS: A sharp edge results from the zero-radius intersection of two planar surfaces. In other words, where the back of a plane blade meets the bevel is the cutting edge. If that edge is honed as close to zero radius as is possible, that edge is as sharp as it can be – a perfect edge. A true zero-radius edge is a purely theoretical thing, but it represents the bull’s-eye of all sharpening techniques and practice. The reason a zero-radius goal is only a dream is because the blade you are sharpening has to be made from something – for instance, steel – and that something is made up of crystals, which are made of molecules, which are made of atoms; and all of these microscopic building blocks have size. However small these microscopic building blocks may be, there is still some there there and it is that little bit of size which determines how close to the goal of zero radius the laws of physics allow you to get. The smallest radius possible is the diameter of the largest discrete particle in the metal’s mixture that can’t be abraded away. I discuss a lot more about edge-tool metallurgy in Chapter Two: What is Steel?

Your fresh and painstakingly-honed perfect edge begins to wear the instant you put it to use; its radius increases, becomes rounder, on its way to becoming dull. If you’re a glass-half-empty type, you might say that there are no truly sharp edges, just ones that are dull or duller. So, it seems that sharp needs a yet more practical definition. A blade is sharp when it cuts what it is supposed to cut according to the specifications of the person doing the cutting. Put simply: sharp is as sharp does.

I tolerate a not-so-perfect edge for certain purposes that for others would be intolerable. How sharp is sharp enough is a function of how much pressure I am willing to apply to the edge and how critical is the surface left behind. Sometimes when I cut a sandwich in half, I cut it with the table knife that I just used to spread the mayo. That knife isn’t very sharp compared to the chef’s knives in the kitchen, but the table knife is handy, will do the job adequately and I don’t have to clean and dry a chef’s knife after I’m done (no stainless steel knives in my kitchen – only old-fashioned, high-carbon steel, treated with care). I may need to push harder with that table knife to cut my sandwich than I would have with a sharper knife, but the difference in this instance is inconsequential.

The sharper the edge, the less effort required to cut with it and the cleaner and smoother the just-cut surface will be (still no biggie where the sandwich is concerned). Similarly, for certain woodworking tasks an extreme degree of sharpness would also be a waste of sharpening time. A scrub plane is used for dimensioning rough lumber quickly, where the surface finish is not the goal, just the final dimension. Yes, it needs to be sharp, but a stropped, mirror finish is unnecessary for the rough work that it is to perform.

Save the strop, and your valuable time, for a blade intended for more precise work – where the surface left behind is more important than a sandwich.

This last statement assumes, however, that you don’t enjoy sharpening and that sharpening blades is a means to an end, a necessary function from which to carry on. As it turns out, many people live to sharpen – finding sharpening a satisfying endeavor in its own right. Me? I actually like to mow my lawn because of the way it looks (and smells) when I’m done. And I appreciate the time I spend doing it as a sort of outdoors meditation, away from the phone and all. Others so dislike mowing that they’ll pay a neighbor kid to do a so-so job and are happy with that. By the same token, some woodworkers will hone and polish their scrub plane blades all the way to a mirror-like finish and all of their edged tools are carefully sharpened and maintained to the same degree. Others want tools that are sharp enough to do the work at hand and want the sharpening process to be as fast and easy as possible: Get it done and get back to the woodworking.

A dull edge has a large radius. A sharp edge approaches zero radius.

I’ve included tips to help the spectrum of sharpeners achieve their goals with both get it done minimal techniques to keep you productive, as well as the gnat’s eyelash types that seek the optical-mirror-flat-back edge-radii that can be measured only using wavelengths of light.

Sharpening is a fundamental woodworking skill – as vital to your woodworking success as any skill you apply to the wood. In his book Woodcarving, Chris Pye says, A master woodcarver once told me that when costing a piece of work, he would allow up to one third of the allotted time for sharpening and maintaining his tools. You weren’t born with this skill – it must be learned. To learn any skill takes practice. Give in to the learning process. The time you spend learning to sharpen will pay off later as it will become second nature to know which grit to use and when, how sharp any given tool needs to be for the task at hand, and when it is time to re-sharpen an edge.

I mentioned that some people like sharpening simply because the activity of sharpening can be so satisfying, like the activity of waxing the car or, in my case, mowing the lawn. We resonate with the results on a fundamental, aesthetic level. But in addition to being aesthetically satisfying, a sharp, polished edge will last longer in use. At some microscopic level, every edge appears as a row of teeth. The size of a tooth is in direct proportion to the size of the abrasive particle that scraped away the steel beside it. The finer the abrasive used, the smaller the teeth that comprise the edge. Coarse-grit sharpening abrasives make relatively large, deep scratches on the steel’s surface that translate to large, saw-like teeth at the edge. Those teeth will cut aggressively at first, but their sharp points are subject to the entire cutting force and will become dull sooner than smaller teeth. If the teeth are large enough, they can leave visible striations on the surface of the wood you’re cutting. Continued honing with subsequently finer grit sizes reduces the size of the teeth along the edge and, as the size of the teeth decreases, the number of them along the edge increases. The concentration of force described above is in effect here: smaller teeth require less force to cut the wood and, with a greater number of them to share the overall cutting force, the teeth will tend to stay sharp longer, leaving a smoother surface behind.

Another reason sharper is better: a polished blade is smoother and slides through wood fibers with less effort, which translates to more control, resulting in a precise, satisfying cut. I have encountered a number of novice woodworkers who have never used a well-tuned plane that has been fitted with a sharp blade. Their only experience with hand planes was typified by the frustration of making a shaving with the neglected and dull bench plane from junior high woodshop. That plane hopped and chattered and instilled a sense that hand planes are horrible tools to use or that the student was not competent to use them. Both sad conclusions, to be sure. But hand these former shop students a tuned-up, plain-Jane #5 with a properly sharpened blade and they go slack-jawed with amazement. How easy to push, how thin the shaving, how smooth the surface just planed, and how very satisfying the experience. It can change lives.

Ommmmm.

Concentration of force: A simple illustration of the concentration of force. Or, which would you rather have step on your foot?

A properly sharpened edge eliminates one important variable when you’re learning a new woodworking procedure. To flatten a board with hand planes is a task that incorporates a number of skills, tricks and metrics. If you haven’t done it, it’s not as easy as it seems, but there’s plenty of help, including many excellent instructional media. Before you can begin to flatten a board, you must be confident that your plane is set up to function properly. It is not an exaggeration to say that all woodcutting operations start at the sharpening station and you cannot be sure of a plane’s performance unless its blade is flat and sharp.

Though not as life-altering an observation as the first-time feel of a properly sharpened plane blade pushing against a wooden surface, polished steel is less inclined to rust than rough steel is. Those water droplets and oxygen pests in the air look for surface imperfections in the steel to cling to and oxidize (rust!). Polishing your blade is by no means rust-proofing, but the shinier the steel surface, the less inclined it will be to rust. I’ll talk more about rust and its prevention in Chapter Two: What is Steel?

A steel sample with both polished and rough surfaces that’s been allowed to rust evenly. Which would you prefer on your plane blade?

Properly sharpened tools can make any task a pleasure; from rough timber work, to fine paring with a chisel.

Though it’s my purely subjective opinion, I feel it important to mention at this point that sharp tools are better tools. There is nothing like the simple pleasure of using a properly sharpened tool. A chisel with a polished, properly shaped edge is more likely to cut exactly where you want it to cut. Hand planing is a delightfully sensuous experience when all aspects of the plane are working properly. The planing action is smooth and easy, there’s a pleasing shisss as gossamer shavings are released to float to the floor, and the surface left behind has a sheen that begs to be touched. The same satisfaction applies to paring with a chisel, bucking firewood with your chain saw, ripping on the table saw or carving your family’s Thanksgiving turkey. Although a thorough discussion of sharpening can be a bewildering mix of physics, geometry and metallurgy, with a dizzying array of gadgets and methods, once you’ve achieved a basic understanding and mastered a few techniques, a perfect edge is easy and quick to create. The process itself is quite satisfying.

The small investment of time spent sharpening your tools makes a huge difference in how they perform – and that’s really what it’s all about for me. I truly enjoy using a sharp knife, chisel or saw and enjoy the sense that it’s just me and the work – the tool acting as an extension of my arms and hands, a willing agent at its design best, collaborating with me on the work to be done.

2 What is Steel?

Steel Things:

1. Golden Gate Bridge

2. Paper Clips

3. Richard Serra’s Fulcrum 1987, PHOTO 2004 BY ANDREW DUNN

4. USS Midway, September 1991, PHOTO BY PHC CAROLYN HARRIS

5. Railroad Yard, Chicago, IL, PHOTO 1942 BY JACK DELANO

6. US Steel Tower, Pittsburgh, PA, PHOTO 2007 BY DEREK JENSEN

IT’S ALL AROUND US IN OUR EVERYDAY LIVES, so much so that we tend to take steel for granted. It may hold up the building you work in. It allows so many things – from your car to your screwdriver – to be the shapes that they are. It’s the hundreds of thousands of miles of railroad in this country and it’s the spring in your ballpoint pen.

Amazing stuff, steel: it can be melted and cast or heated and forged into complex shapes; pulled through little holes to make wire; hot rolled into structural shapes, or cold rolled into sheets that are then bent, stamped, rolled or spun into ships, washing machines, the internal structure of your television or computer. In so many ways steel is more valuable to us than gold. Imagine if all the gold in the world suddenly disappeared: monetary disarray, yes; a bling crisis and dental problems, certainly. Now, imagine if steel disappeared. Think of all the things that rely on steel that would simply collapse or cease to exist. The skeleton holding up the man-made world is made of steel.

It’s easy for any of us, woodworkers included, to take steel for granted. Think about it: much, if not most, of the actual work of woodworking depends on a piece of steel somewhere between you and the wood.

What is Steel?

Steel is a mixture – an alloy – of iron and carbon. Iron, without any alloying elements, needs help to make it truly useful in all the structural applications we ask of it. Though iron may have been a wonder during the ascent of man – harder and tougher than gold, copper or bronze – with the addition of very small quantities of carbon, as little as 0.2% (two tenths of a percent), the wonder that was iron turns into steel – a very different, incredibly strong yet malleable material. That little bit of carbon adds enough-strength to make steel a suitable material for bridges, high-rise buildings, cars and refrigerators.

Most of the steel that we encounter is 0.2%, low-carbon, mild steel and is available in hot-rolled or cold-finished sheets, round bars, flat bars, I-beams, angles, etc. Hot-rolled steel is the most common structural steel and is used for building and bridge superstructures, big ships, and such; it’s the rough and dirty workhorse of the steel industry with a layer of heat-induced iron oxide, called scale, over its entire surface. Cold-finished (also known as cold-rolled) steel with its smoother, more attractive surface, can be rolled to a more accurate thickness, or gauge, and