During the last eight years I’ve tried to refine how I explain how to use a handplane to students. The biggest problem the students have isn’t ignorance. I wish that were the case. Instead, their biggest problem is they have been flooded with so much contradictory information that they are paralyzed.
So I’ve been trying to increase the signal and decrease the noise so they can focus on what is important. To help cement these ideas, I’ve created a list of principles relating to handplanes. Here are the ones for the tool’s cutting edge. The most important one is No. 10.
1. A sharp edge is two surfaces that intersect at the smallest point possible. This is called a “zero-radius intersection.”
2. A dull edge is where damage has occurred (hitting a nail) or the zero-radius intersection has worn away to create a third surface at the intersection.
3. A zero-radius intersection will not reflect light. The third surface created from wear will reflect light. So you can see a dull edge as a bright line. You cannot see a zero-radius intersection.
4. In general, a tool can be made sharp (a zero-radius intersection) by ANY medium – from a grinder to a waterstone. Polishing the edge only makes it more durable. The more polish, the longer the edge will go between sharpenings.
5. A sharp edge is TWO surfaces. Both must be polished for the edge to be durable. But only a small portion of the edge cuts wood (about .010” on each surface). So do not waste your time polishing steel that does not cut wood.
6. There are only three grits in sharpening: grinding, honing and polishing. Grinding removes damage or an edge that has been oversharpened. Honing removes a dull edge and restores the zero-radius intersection. Polishing makes the edge more durable. All other claims are marketing.
7. The larger the angle between your two surfaces, the more durable the edge. However, large angles can make tools unusable. If you sharpen an edge above 35°, you have to educate yourself about cutting geometry and clearance angles to stay out of trouble. If you sharpen at 35° or lower, you’ll stay out of trouble.
8. The smaller the angle between the two surfaces, the less durable the edge will be. Edges that are sharpened at 20° or lower do not work well in planes.
9. Plane edges can have a curve or be straight. Both perspectives work.
10. There is no such thing as “cheating” when it comes to sharpening. Use jigs and fixtures – or don’t. There is only sharp and dull.
— Christopher Schwarz
Perfectly said. The world needs to get past sharpening and build stuff.
‘Zero-radius intersection’ ? There must be a more user-friendly term for it than that, surely!
“Line”. Mathematically correct, even.
Only if both surfaces are planar…
I thought a “line” traversed indefinitely in both directions. Wouldn’t a “line segement” or just “segment” be more accurate? 😉
Chris,
When you say ‘there is no “cheating”‘ in no 10, do you mean, one should or should not use fixtures, jigs or similar? The way the sentence is worded, it could be interpreted either way.
Thanks for the great post! As someone who has struggled with this in the past, these are very helpful principles and wish I had encountered them sooner.
Aaron
Chris advocates the use of honing guides, especially for beginners. And as a beginner, I totally agree with him. Using a guide is not “cheating”!
Aaron,
A good point. Let me rephrase (and I’ll correct it above).
There is no such thing as “cheating” when it comes to sharpening. Use jigs and fixtures – or don’t. There is only sharp and dull.
I was thinking same. ‘Cutting edge’ maybe?
I took your class this past weekend at Marc Adams… and I have this same list of 10 principles in the form of the handout that you gave us. My .02 is that these principles really help and you did a good job teaching them. You’re absolutely right, I had read quite a bit about handplanes and just reading wasn’t cutting it. It was good to see it in person, and to have some no nonsense info that I could easily put into practice.
Reblogged this on Russell's Rants and Raves.
Thank! You! Finally someone said it… We do live in the information age, but reading too
much about something tends to confuse and bewilder. I say just get out there and figure it out
for yourself. I personally love those “ah ha!” moments and it is a very rewarding experience.
Life is easy… unless your just bored and feel like complicating it , just sayin’.
Cheers!
Chris’s “point” (hmmm) is well-made. Sharp is a very simple place, you will know it when you get there. The difficulty for many folks who are trying to find the way to get there are bombarded with too many opinions. Want to see a woodworking forum go out of control – say one type of sharpening is better than another…
It seems everyone has their own religion when it comes to the sharpening process, and many think that thier way is the way everyone should do it; if a person’s approach is comfortable for them and arrives at “sharp”, why is their approach wrong? There is no “best” way to sharpen, despite the many who claim otherwise.
Chris characterizes sharpening as a “gateway” skill for woodworking, so only an approach that is comfortable for a user will be used frequently enough to be useful for their woodwork. Find an approach that works for the person, they will use it more often and they will find their happy sharp place with less effort!
You sort of covered it in #4, but for me, the biggest thing was that you can use any medium. I started with sandpaper, then went to waterstones, then diamond, then back to an upgraded set of waterstones, then, I finally settled on oilstones. All that money spent could have been used for more wood, or tools!
I have heard many people say to find a method and stick to it. But, what I really should have done, is to have researched all the options, and then decide.
Each medium has it’s advantages, and one needs to weigh them against each other to figure out what works best for them.
I followed a similar arc in sharpening. I started with one old oilstone for honing then moved on to a range of diamond stones and then to waterstones in pursuit of the “perfect” method. Like you, I often think that I should have been able save money and time by researching the methods and decide which is “best”. In retrospect I have concluded that I really needed to try all of the different methods to properly evaluate and compare them. The best way for me to do that was to buy the equipment and try it out. It took years. The upside is that I now know how to get to sharp using all the various methods and which work faster for certain types of steel, which are more durable, which are more messy, which are more portable, etc. The whole process was very liberating because I divorced myself from strident opinions about one method being better than another and learned to focus on the objective: SHARP. Moreover, I do not fret about sharpening methods any more. My goal is to get the iron sharp with whatever method is at hand and get back to making shavings!
I am hopeful that Chris’s efforts to demystify sharpening will shorten the journey for other woodworkers, but I wanted to offer the opinion that trying different methods is not a waste. Education always costs something.
I think you should have included no. 11 I learned from your classes. To paraphrase: Choose one method and stick with it. Thats the only way to master the skill and gain the necessary finesse. No matter how much it initially frustrates, irritates, disappoints, or looks less sexy than the alternatives, STICK IT OUT!
Or was this your advice on a successful marriage … I can never keep those two straight.
Good post. I do have a question about number 4, though. I’ve been working on shaving with a straight razor for a few months and have learned a ton about sharpening. My question about 4 is that if I tried to shave with a razor coming off a 4000 grit stone, it don’t think it would work very well at all. In fact, I had to go to .5 micron diamond paste because the 8000 grit stone wouldn’t get it sharp enough. So it seems to me that polishing does more than just make the edge more durable. With a lower grit it seems like you might have some sharp and dull points on the edge due to the relatively large scratches. Am I just overthinking this?
Wet shavers need a post just like Chris’s with “beard” substituted for “wood” in every instance. “How did men shave prior to diamond paste?” is just as relevant as “How did hand plane users possibly work before $250 water stones?” Sharp is sharp. You have to learn and practice your way to it rather than spend your way there.
Chris,
Strops. Stropping compound takes you to the same level of polish as any waterstone.
And skill and practice help a great deal. Remember that abrasive breaks down into smaller rocks…
For #10, I could only hear Yoda… “Sharpen, or sharpen not. There is no ‘cheat.'”
“There is only sharp and dull.”
Why do I picture you saying this while sitting on the top of a mountain in a gold robe?
Next you’re going to tell me, “There is no blade.” It’s like the Matrix of sharpening, and you are the Schworacle.
Number 10. is my favorite now. I’ve been called on this so I know better. And I see my question about the role of stropping has been answered. I’m restoring a profile on a nicked Howland No. 12 round (7/8 in). Timely. All rules apply.
I should add that I ordered some LN replacements to try my hand at hardening and tempering. I’ll try to keep the MAPP away from the flammables.
Someone laid claim to No. 11, so let’s call this No. 12: if a blade is used today, it gets sharpened today.
As part of the shop shut-down process, I’ll hone any blade I used today. I don’t use jigs, and it rarely takes more than 30 seconds/blade, whether it’s a chisel, plane iron, whatever. Benefits: that tool is ready to go back to work the next day, really *looking* at your tools at the end of the day encourages the very minor preventative maintenance that hand tools require, and the constant practice will develop the feel required to leave the jigs in the drawer.
I’ve learned that this habit is a little hard on waterstones; I may switch to oilstones when the time comes. It also has me re-thinking the necessity of hard(er) tool steel; if you’re sharpening frequently you don’t need an iron that can hold an edge forever. Slightly softer steels and oilstones may make more sense for tools that are being used every day.
I think for me the biggest breakthrough in my sharpening ability was when I built a dedicated sharpening station so I could leave my sharpening equipment out and ready while I was working. That way, as soon as a tool starts to feel “different” it’s just a step or two away from my bench to touch up the two surfaces. It wasn’t something I decided to do lightly either, given the tiny space I have for my shop. But it has really paid off for me. Sharpening is no longer a chore I have to plan to do when I reach a good stoping point. It has become an integral part of my work and is usually the last thing I do before I quit for the day. As Chris says, sharp fixes everything! I’m definitely a believer.
A local wood carving teacher taught me how to make the best honing wheel ever! Cut circles out of mat board and glue the layers up with Elmers. True up your new wheel with coarse sandpaper, (a dusty process). Charge it with honing compound. My tools are now made razor sharp in only a matter of seconds.
We can call this No. 12: if you used it today, you sharpen it today.
As part of my shop “shut-down” procedure, every edge tool used gets sharpened. Usually this means only a re-polish on the 8000 grit waterstone, and takes no more than 30 seconds. The benefits: the tool is ready to go to work the next day; you never deal with a time-consuming major re-sharpening; taking a good look at your tools at the conclusion of your work encourages the minor amount of preventive maintenance that hand tools require, and the constant practice will quickly develop the feel required such that you can leave all the jigs in the drawer.
I’m learning that this is a little hard on waterstones; I may switch to oil stones when the time comes. It also has me re-thinking my notions of proper steel hardness — for a tool that gets honed every day, slightly softer steel might make more sense.
There’s a lot to be said for really *knowing* that when you pick a tool, the edge is ready to go.
oops…sorry for the duplicate post. WordPress didn’t tell me the first one made it. Apologies. Mod, feel free to delete.
I started out with waterstones and wet dry paper on glass, then micron diamond sheets. I now use Shaptons, a Dia-flat plate to keep them flat, and micron paste for honing. Along with honing guides. That is my story and I’m sticking to it.
I appreciate you trying to distill this down into a few concise points and “cut through all the crap”, but unfortunately life isn’t always that straightforward. The paradigm of “two perfect planes intersecting with a zero radius” is an idealized concept that cannot be actually achieved; it’s just a goal to strive for. I’d be interested in hearing your – and others – thoughts on “how sharp is sharp enough?” In my experience, this varies with the tool and its intended use – for example; I have higher standards for the sharpness of a paring chisel compared with a mortise chisel; ditto for smoothing plane versus fore plane.
I’d also like to echo the sentiments of other posters in saying that you should choose one method and stick to it until it becomes second nature. My choice has been water stones (with a honing guide) and I’m pretty comfortable with that. BUT – and this is a big but – I’ve also found that the ability to hone freehand on oil stones is a very important skill to have if you are working outside your own shop. This is, as far as I am concerned, the absolute essence of sharpening, requiringthe least equipment and making the least mess.
Excellent rules, and an outstanding thread. Question about waterstones… will it hurt them to leave them in water all the time? I don’t have to worry about freezing even in Winter here in Las Vegas. We sometimes get below freezing, but not inside my garage.
Love the Yoda quote! I could ‘hear’ it too! May da Schworacle be with you!
Depends on the stone. Some stones turn mushy. Some combination stones become delaminated. Some don’t.
So check with the maker.
I’ve left my Norton waterstones in water for up to a week with no ill effects. On the other hand, I worry less about soaking them now than in years past. Get them good and wet, spray them down every so often, and they work just fine.
My King brand 800 and 2,000 grit stones have been submerged continuously for more than 6 years now. The 800 grit is about half its original thickness due to more frequent flattenings, but both are intact and still performing fine.
Totally agree about #10.
Until you run into a blade that doesn’t work on your jig or fixture. No matter how good you were with the jig, without it, you are still the green newbie you were the first time you used the jig.
At that point, you have cheated yourself.
Ah, who am I kidding? Just go buy yourself a jig, and get to work… The truth is that there is no such thing as “sharpening police”, and if they do ever show up at your door, you are allowed to give them a wedgy.
It’s mildly ironic that all the advances in abrasive technology have made the job of maintaining a decent cutting edge on a few tools so utterly confusing and complicated. Until about 1880 and the development of artificial oilstones, all they had was whatever natural stones happened to be available locally, and leather strops. Still managed to build any amout of stunning furniture, buildings, ships, you name it.
Maybe keeping things simple is not such a bad idea.
One of my favorite Blues songs! ‘Keep it Simple’ by Keb’Mo. Also love ‘France’ by him too. Happy Blues seems like an oxymoron, but darned if that’s not what it is. I think I fractured the rules for English just there!
Great post. I would add one thing – #11 or perhaps even at #1: Before you do anything, check to see that your stones are flat. As one who has bought a lot of chisels on eBay, if I could make a wish, it would be to wish out of existence all those old oilstones with big hollows in them, lurking in back yard sheds all around the world. I hate to think how many hours I have spent taking the humps out of the back of otherwise beautiful old chisels.
I would qualify #7: If you’re using a low-angle bevel-up plane, you’ll stay out of trouble to at least 50°. But you do still need to understand the pros and cons of such a high angle.