Sharpness? – Paul Sellers’ Blog

It is hard to explain sharpness. Pick up a neighbour’s kitchen knives to cut with and nine times out of ten you will struggle to slice into butter even if you heat the blade. For the longest time it was the same with woodworker’s hand tools and especially in the so-called professional realms. Just when that happened can be easily pinpointed with the advent of so-called power tools. Within a decade or so hand tools all but disappeared and today we are left picking up the pieces of the saddest skill levels in the history of woodworking.

A continuous macro-camber to a cutting edge rarely ever fractures because of the amount of backup steel you get immediately above and behind the cutting edge.

A simple post on my Facebook often stirs up a gathering of the malcontents. My intention is to find out what the biases are but also to come back with just answers for them and others to understand and learn from. From their comments, I quickly discover many of the problems affecting the woodworking world alongside the erroneous teaching they have absorbed from woodworking machinists. That’s why I wrote my second book Essential Woodworking Hand Tools.

Essential Woodworking Hand Tools
My book is crammed with masses of my hand drawings, illustrations and pictures and text written from almost sixty years of daily full-time woodworking as a furniture maker. The best tool in the shop, some say.

The book itself became the most essential tool because it was written with the intent to bridge the gap caused by a loss of a couple of woodworking generations in the woodworking world. here I was teaching classes for amateurs and understanding the more where the shortfall was. That generation lost was now being taught that the only progressive way forward was not to master and establish skilled woodworking but to use miniaturised mass production methods used in industry to make even a single dovetail, mortise and tenon or whatever. The assumption that this was progress was based on the misconception that no one today could cut that dovetail accurately and quickly by hand. That’s when I stepped in. I’d always taught from a lived life working with hand tools; fifty years in the saddle gives you a balanced perspective and a knowledge base to work from that never seems to dry up. In a dispute with a publisher of one of my books, I parted ways early on and at great cost to myself. My woodworking friend, a marketing consultant to large international companies advising me said, “Never mind, Paul, they have the drop in the bucket. You have the well!”

Mesquite is almost twice as hard as oak. A macro-camber resists edge fracture and feels no different than any other bevel type used in woodworking yet it is faster than any to establish and maintain day-to-day. Give it a try for a month of daily work and then decide for yourself.

So what is sharp? Let’s just focus on a chisel edge and see all plane edges as chisels. We sharpen almost all of them in the same identical way. A bench plane iron is just a wider version of a chisel.

The first assumption to deal with is the one that says everyone sharpens an edge tool with two bevels. I don’t but I could. I never would, not really. No good reason to although in experiments I have and do.

This is the most common cutting edge used through the last century in general woodworking with hand tools like chisels, planes and spokeshaves. It’s the basic hollow grind created on a mechanical or electric grinder at 25º followed up with a secondary bevel that is honed to finalise a cutting edge at 30º, usually on a sharpening stone.

The second assumption is that you always grind the first, main or primary bevel on an electric grinding wheel. I don’t but I could.

Using an electric grinding wheel can speed up the process of removing a lot of metal to reestablish a bevel to an edge tool but most often, perhaps once in many hundreds, it’s far from necessary. You can use a coarse abrasive of any kind to grind down to a fresh edge and that should take no more than 10-15 seconds provide you approach it freehand.

This new first-level abrading removes the old, worn bevel to reestablish a perfect profile. It’s a macro-camber and is the most efficient way to get to a cutting edge for any hand tool woodworker using hand methods. This level took 15 seconds.

Another fallacy is that the second bevel is called a micro bevel. You can call it what you want but a secondary bevel works just as well as a name because the increased angle literally necessitates a second bevel be that small or large. The one above might be referred to as a secondary bevel but in terms of sharpness, it is no less sharp than a micro-bevel. Many things offered as new and innovative are little more than trendy terms and clickbait than helpful — even before clicks were invented!

What would you say if I said you never need to grind your chisels on a grinding wheel again? Moreover, that grinding on a machine only ever slows down the process. What if I say that you never need two bevels ever again? Or that a cambered bevel will prove stronger and last longer than a micro bevel? The only way to prove and understand this is to actually do it.

This bevel is cambered and begins right at the cutting edge and goes in a continuous sweep to the top flat face. Whereas it looks as though it has a bevel near to the cutting edge over on the left, it doesn’t. The shape for a macro-camber like this is more like the quarter of an ellipse.

Now, though it is completely unnecessary, let’s say I allow you the one-time use of a grinding wheel to create a cambered bevel. To do this you set the chisel at around 30º and slide the chisel upwards as the wheel rotates. This will negate a hollow grind and cause an elliptical quadrant to the bevel. You may need to do this two or three times until you get the shape you want. Effectively, that starts at 30º then tails off and can be as far along the camber or the length of the chisel as you want. This picture shows what you are aiming for. This initialsing of the chisel is a one-off deal. You never need to do it again. But you actually don’t have to do it. The camber will establish itself;f over three or four sharpenings. Soon you will be freehanding your sharpening with the periodic use of a honing guide to ensure you don’t steepen the curve at the beginning of the chisel edge.

This ground bevel is a hollow grind from a coarse, 8″ wheel and must have a second bevel to create a viable cutting edge. Wide or narrow, one will be just as sharp as the other but the narrower the width of this secondary bevel the weaker it will be.

The secondary bevel came in with the increased use of small-wheeled electric grinders that became more ubiquitous during the late 1950 and 1960s. Today, almost all woodworkers will own a bench grinder. Take a chisel or plane iron off the grinding wheel as shown above and the cutting edge will not be viable until it is strengthened by adding a second bevel.

So, even though grinding metal on a grinding machine cuts steel very fast, the faster it cuts the more the steel burns This burning blue at the cutting edge detempers the steel where we need consistent hardness the most. The cutting edge then dulls far more readily and usually crumples under any and all pressure too. This is highly negative in our world of edge tool use. To repair this issue we must grind off the damaged area or resharpen ten times more frequently until we get through to good steel again.

Above you will see three chisel edges. The one on the left is sharpened with a hollow grind

I think drawings show more than photographs.

Hollow grinding goes back centuries but not all crafting artisans owned a sandstone wheel to hollow grind. Today of course almost everyone owns a grinding wheel of some kind but it is not true at all to say that grinding is the fastest option. I doubt that most people sharpening using a mechanical grinder can achieve the edge I do using a camber and hand sharpening. A chisel or plane iron takes me under a minute every time.

Some woodworkers prefer to use something renamed a micro-bevel system. Whether they grind a flat bevel as the primary bevel or a hollow bevel, the edge is strengthened using a second bevel. Some say it is faster but I very much doubt that that is true. Just installing the chisel into or onto a guide takes time and then actually grinding it accurately is time-consuming unless you are experienced but even then it takes more than a minute to do. From there you still have to hone that bevel. Whereas it is not too long, the interruption of using a grinder seems always to get in the way.

I adopted this method as an apprentice because all of the men I worked with went from dull to sharpening stone to strop and back to work. There was a grinder but it was used only if someone hit metal in the wood or perhaps a stone at the bottom of a door in for repair.

I call this the macro-camber to counter the term micro-bevel. The time it takes me to sharpen is yet to be beaten by any other method that includes a mechanical grinder but that is not really the reason I use it. Some things are just intrusive, have questionable unnecessary safety elements and are just plain slower. Of the thousands I have taught to use this method, few have ever returned to the grinding wheel even though they already own some very fancy rigs. Why? They just found that once they established the method and repeated it enough to become reasonably skilled and proficient, it was just the best method they had ever used and they felt in confident control.

Of course, major nicks in cutting irons cause major impacts on the wood we chisel or plane. Ten strokes with a plane with a nicked iron will leave a surface like a shunting yard for trains. Would I use a grinding wheel in such cases? Well, here is the thing. If the iron is set for a deeper cut, hitting a nail, screw head or embedded pebble will take a bigger chunk out of the cutting edge. In that case, and with impunity, I would definitely use a grinding wheel. If the plane was set shallowly, the nick might, luckily, be very minor. In that case, I would at least try the 150-grit plate or abrasive first. if after ten or so rubs it was gone then I would go further in my refining without using the grinder.

Grinding wheels have their place. Remedial work for deep damage cuts away the excess quickly to regain the edge you need for honing. But though the grinder creates an even hollow if held steady and square, you can create a camber by offering the bevel to the wheel at near 30º and instead of staying there, slide the chisel in an upward movement and you will have q decent 30º start to the bevel and, through that upward movement, create a very nice camber.

The low-level presentation to the wheel at 30º as a start . . .
. . . and followed through with an upward push that takes the cutting edge away from the grinding wheel to focus in the tail end of the bevel.
The roughed-out camber from the grinding wheel looks like this. This is an initialisation step and needs never to be done again.
Now go to the sharpening plates and hone to 1200 grit and then . . .
. . . follow on with buffing out on the strop charged with buffing compound to 10,000-grit or thereabouts.
The bevel will look like this . . .
. . . and cut effortlessly like this.

From now on you never need to grind on a grinding wheel again and the whole sharpening process should take about one minute per chisel

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