Is there a 'best' way to sharpen an edged tool like a chisel?

Question

There are a bewildering variety of sharpening methods out there and many opinions as to which might be the best.

Is there a best way? What are some good references on the subject?

Answer 1

Tl;DR

Let me begin this answer with the final conclusion: all sharpening systems work. Just pick one and live with it because none of them are any fun.

I use a set of Arkansas oil stones from Dan’s Whetstones and use the Veritas honing guide. I’m slowly trying to learn to do this freehand and wean myself from the honing guide. In addition to the stones, I have a piece of leather that I glued to a piece of wood to strop with. I rub it with a stick of chromium oxide to give it a bit of grit. For other things like carving tools with curved profiles I attempt to use a small slip stone and a leather strop with profiles molded in it but I’m terrible at it and don’t feel I have much to contribute there.

Having said that, here are the resources that I have used to learn about sharpening:

Book: The Complete Guide to Sharpening by Leonard Lee (of Lee Valley Tools).

DVD: The Last Word on Sharpening by Christopher Schwarz. His philosophy here is: sharpen often, do it quickly, get back to work.

I’ve struggled a bit with which type of sharpening media to use. I’ve tried sandpaper (the Scary Sharp method), diamond plates, and traditional Arkansas oil stones. I’ve also used the famous Tormek machine.

Sandpaper works very well. I bought a $5 marble floor tile and used this system for quite some time. I eventually decided that it was a pain to have to go restock my sandpaper so often and also a pain to stick it down and then have to scrape it off the tile every time. I wanted a more permanent system.

I also tried diamond plates but had a strange problem: they seemed to wear out which is exactly the opposite of what is supposed to happen. I submitted a question to woodtalkonline and got this response. It is long but very good – answered by Larry Williams who is a maker of traditional wooden handplanes in Arkansas and is an expert on the subject of sharpening. (I actually stopped by his shop once while in Arkansas for the weekend. He and his business partner were the nicest guys ever and I could hang out with them for a year and not learn all that they knew.)

The Tormek is the best of all but is way too expensive for me to invest in. My friend has one and I have to say that it really does work as advertised. It produces a sharp edge at a rigidly controlled angle and it is quick (but first you have to fill the trough with water and then clean it up afterwards.) I would buy one if I could justify it. If money is no object, go buy one of them.

Anyway… several years ago, I had to attend a funeral in Arkansas and chose my route so as to pass by the quarries of Dan’s Whetstones and while there, I got a tour, a lecture on sharpening, and two traditional Arkansas sharpening stones and that is what I now use for everything. I wrote about that little field trip over here.

So that’s what I know and how I came to know it. Everyone makes a different decision but my point is to simply make a decision and go with it. If I wasn’t so cheap, I probably would have bought a set of Shapton Waterstones years ago because I’ve seen so many people online use them. The subject of sharpening is fraught with almost religious fervor and narrow mindedness but the links above are links to people who seem open minded and perhaps scientific.

Answer 2

The most important part of sharpening a tool is knowing where to remove the material from to restore the edge.

On wipedia's grind page there is a description of the most common ways to put an edge to a blade.

A chisel, for example, will most often have #4; a flat surface on one side and a angled face ground off. To sharpen this you need to remove material from the angled face evenly until the edge is sharp again.

Answer 3

For maintaining a sharp edge frequent light sharpening will serve you best as this will limit wear and heat (after a couple hours using a tool a couple light strokes across a wet stone as part of your cleanup process is often all you need). Restoring an edge is much more difficult as you need to take hardening into account. If you have an old beat up tool to sharpen I would remove the handle (if possible), anneel it, grind it and re-harden. But note that I am a better blacksmith than woodworker.

Answer 4

In short, no. Diamond plates, waterstones, oilstones, abrasive paper/film, grinders, paper wheels and conventional strops can all form part of a sharpening system capable of creating the very sharp edge needed for a chisel or other edged tool used in woodworking.

If you're after a simple 'trick' to make the process more repeatable then I strongly recommend a sharpening jig. But not one of the commercial types, you can make one from shop scraps and a couple of machine screws or bolts. And as basic as it looks that works as well as any commercial jig (and actually better than some, because the wider base almost completely solves the rocking problem which is inherent to single-wheel designs).

Here is another very simple jig that shows how simple a jig can be and still work well.

I would however still encourage you to work on your hand sharpening, it's a lifetime skill and while it takes practice and dedication to get good at it it more than repays the investment in time with the speed and efficiency with which you can form sharp edges and maintain them. Working by hand you can easily do a top-up sharpen on a chisel in under two minutes, before many tools and jigs have even been set up properly, much less the time needed to pre-soak a waterstone. And if you use stropping the keenest edge can be put back on your chisel in as little as 10 or 20 seconds.

Strongly recommend you check out Paul Sellers's videos showing him sharpening and talking about the process, they're clear and unambiguous and boil the process down into the simplest steps. And his results, as you'll see, speak for themselves. To get you started, here's one showing him sharpening a cheap chisel start to finish.

Answer 5

I would say, having tried several methods (freehand with a whetstone or diamond stone, with a honing guide on a stone, and using a wheel type grinder/honer) that using a wheel type grinder/honer is by far the quickest, easiest and most consistent way to do it.

I'm talking about this kind of setup where you have a stone wheel on one side, a leather honing wheel on the other side and an integrated guide to keep everything straight.

It is not the cheapest way, but looking at a good 3-piece diamond whetstone set (coarse to smooth), this grinding/honing wheel system actually only costs about 25% more.

There's also a number of videos (such as this one) which show the best way to use them.

The wheels, motors etc. also seem to last an awfully long time. I work in a joinery shop with ~20 employees, so a lot of sharpening goes on, and I think we've had our wheel setup for 4-5 years without having to replace anything.

Answer 6

There are really two aspects to sharpening chisels and plane blades - creating a primary bevel and then honing the edge. The angle and surface finish of the primary bevel is not critical - it can be off a few degrees and can be relatively rough. Many methods can be used to create it: bench grinder, disc sander, belt sander, coarse diamond stone, sandpaper, etc. I prefer a bench grinder with a friable wheel and a jig to hold the tool because it is quick. The real challenge is in honing the edge.

There appears to be universal agreement as to what constitutes sharpness – from Ron Hock:

“A sharp edge only exists where two planes (i.e., the back and the bevel of a plane iron or chisel, or the two bevels of a knife) meet with zero radius. “

There does exist, however, significant discussion about how to get there. One of the main areas of discussion is free hand vs. jig use. I was never able to achieve a razor sharp edge (plane or knife) free hand. I’m sure part of that is learning the skill. However, referring to the accepted definition of a sharp edge, it is impossible to get as close to a zero radius free hand vs a jig. One may get close enough for their personal taste/use, and it will be quicker than using a jig. But, the free hand radius will not be as small, and will likely contain several edge lines along the length of the edge, and will therefore not hold a usable level of sharpness for as long. So, over a period of use, the extra time to use a jig is paid back through extended edge life.

Also, the smoother the edge is the longer it will last. The more serrated an edge is the quicker micro fractures of the steel occur and the edge wears down more quickly. Many support the use of stropping edges on leather with one of many compounds. While stropping will produce a sharp edge (I can shave hair and cut paper with it!), I am not aware of any of the compounds having grit as small as the 0.3um film I use. The larger the grit, the more of a serrated edge and the faster the edge wears down. Stropping is typically done freehand, and it is impossible to hold an angle as well as a jig. Wet sharpeners, such as Tormek, Grizzly, Sheppach, at least hold a constant angle, however the stone, even dressed to fine, leaves relatively large scratches, which result in sharp, serrated edges that break down faster. If you can find actual submicron compound, and use it on a fresh leather wheel of a wet sharpener, on a blade that has been honed down to 5um or less, then you might be in business.

Another issue with stropping – what happens to the metal particles that are worn away? The wire edge that may be broken off on the strop? There is no way to clean the metal particles off the strop. They embed in the leather (or mdf or other soft substrate) to continue to scratch up that edge and add serrations to it.

While there are many honing methods that the user is satisfied with, using a jig and creating microbevels is the best way. Here is a link to my method.