Chisels, What is Sharp

[Richard Wagner]

I have tinkered in a wood shop for many, many years and one might think this is a question that I should have had answered many moons ago - but I did not.

I have always hand sharpened my chisels (at least I thought they were sharp) then my kids gave a a WorkSharp for a birthday gift and then a set of Buck Bros. chisels for father's day.

When I got through making sure the backs were flat and the cutting faces had all been ground to the bevel I thought I wanted - I had what I thought was a real sharp set of chisels. But, I had only used the two coarsest grids that came with the WorkSharp.

By the time I had finished with the next two levels of grit, the faces of these chisels are without grind marks of any kind. They sure are pretty but are they really anymore functional, as a chisel, than what I have been using for years?

I think the same questions apply to the blades for my hand planes too but I have not done them yet.

What bevel angle should I be putting on these chisels and planes?

[Ken Werner]

Richard, in my opinion, a sharp edge has no visible grind marks at all. The edge should be the intersection of 2 mirror polished surfaces.

I think if you experience really sharp, you'll see the difference. Perhaps there is a local woodworker who can show you his/her edges.

Ken

[Mike Henderson]

The bevel angle on chisels depends on what they're going to be used for. I sharpen my chisels to a 25* angle then put a secondary bevel to suit the work - maybe 30* or even 35*. If I'm paring, I leave it at 25*.

On a plane blade - assuming you're using a bevel down plane, the only limit is the clearance angle. If you have a 45* frog, I'd sharpen the blades to 35* to get more strength.

[I'll add a comment about some of my chisels. I had a set that I thought was fairly bad so I put it aside some years ago. Over the years, I've taken classes, practiced, and learned a bit about sharpening. I got those old chisels out a while back and sharpened them up. It's amazing how much chisels improve after they've sat in a drawer for a couple of years.]

Mike

[Tri Hoang]

Bevel angle depends on what you are going to use your chisels or planes for. For example, I'd have my paring chisels primary at 16-18 and micro at 20. Utility chisels could be 25 to 30. Mortise chisels - I have these at 20 primary but 35 secondary (1/16 wide).

For plane blades - typically 30-35 for bevel down. Bevel up is a completely different animal. My general smoother, LA jack, is set at 30 primary and probably 33 micro. My BU smoother is set at 38 primary and probably 40-42 micro. The trade off here is between a reduction in tear out and shorter edge life.

There are a number of ways to test for sharpness. Most common is the shaving test. But it does not tell you a whole lot except that after a while, you'll have a clean forearm. Another is paring the end grain of softwood such as pine. It should take paper thin shavings with minimal effort and leave a smooth/wet-looking surface. Still another method is to drag the edge across your thumb nail. It should feel smooth and not catchy. If it isn't smooth or catchy, you got a nicked blade.

With the WS3000, watch out for bubbles. I'd also won't strop my plane blades on its leather wheel...just too easy to round off.

[Mark Maleski]

To answer the question "what is sharp?" I think you must look to the results of the cut, not to the appearance of the tool. Richard, you didn't say whether your chisels provide a better cut now that you've achieved a shinier finish. I suspect you did but...come on, don't leave us hanging!

BTW the air harm and fingernail tests might be informative, but ultimately it's the quality of the wood shaving that matters. Depending on the bevel angle, end grain may/may not be the way to test.

Mark
Herndon, VA

[Michael Faurot]

For me, it's being able to get an edge on a tool as quickly and easily as possible and then be able to shave hair off my arm. For me, it's that simple.

Unless you enjoy sharpening your tools as much (or more) than working wood, it doesn't really matter which way you get the tool sharp.

[Jim Koepke]

It's amazing how much chisels improve after they've sat in a drawer for a couple of years.]

Mike

Is that the patented drawer hardened steel we have heard so much about?

:D

jim

[Carl Maeda-San Diego]

One test I use to see how sharp my chisels are is to pare end grain with it. If you can get nice curls easily then I consider it sharp enough for me.
As for bevel angles, I use a 25 for primary and 30 for secondary. Although I do have a few chisels with a 35 for secondary... I use those for dovetailed pine drawers. On softwoods, it cuts easier.

[Richard Wagner]

I want to thank all who have responded for the lessons and encouragement that your words have provided.

Yes, I think my chisels probably perform better than in the past (even though I thought they were sharp) but I am certain that they still would not pass some of the tests that have been suggested here. I just don't know but I will certainly try to learn. Specifically, I did not know to check how well the planes or chisels will perform on cross grain. I will do that with a couple of the chisels that I think are finished.

I do have one new question, however, that arose from one of your responses. I have NOT polished the back side of the chisels to the same degree as I have the bevels. Should I be doing that with all my chisels? Turning chisels as well?

I gotta go sharpen some chisels now but I'll be back. I know there is a lot more for me to learn here. Geez, I wish I had started this when I was twenty.

[harry strasil]

FWIW, I use my thumbnail at a 45 and set the edge on it, if it doesn't slip on the nail its sharp, and I never waste time polishing the rest of the chisel, just hone the cutting edge its all the does the cutting after all.

The other sharpness test I use is to pare the end grain of a piece of old oak, If I can make a shaving its sharp.

[Sam Takeuchi]

you don't have to make the back shiny like the bevel side. As long as it's flat, smooth and relatively scratch free, it'll do even if it looks a bit hazy. If you truely want to get shiny back, you can rub some green polishing compound onto a MDF or something, rub the back of your chisel a few times. It'll be very much mirror like. While it's nice and all, personally I don't think it's necessary. I'm more of "do what works for you" guy than "this should do such and such" type, so I say try it, if it works within reasonable amount of time, then certainly it's nice to do, but if it takes too much time, then don't bother trying to get mirror like shin on the back. As long as you think your blade is sharp, that's what counts as long as it's not causing problem.

[John Keeton]

Geez, I wish I had started this when I was twenty.Richard, no you don't!! Then you would just have had more years to fret over how sharp your tools were!!:D

[Michael Faurot]

I do have one new question, however, that arose from one of your responses. I have NOT polished the back side of the chisels to the same degree as I have the bevels. Should I be doing that with all my chisels?


They do need to be flat, but they don't necessarily need to be shiny.



Turning chisels as well?
Most turning tools don't need to be sharp the same way plane blades and chisels need to be sharp. Gouges, parting tools and such just need to be touched up on a grinder and that's about it. I do like my skew chisels to be a bit more finely ground, and do that on a slow speed wet grinder. But for the most part, the lathe is turning the wood beneath the cutting edge of the tools at X number of feet per second. The lathe does most of the work, so you don't need a super sharp edge. It doesn't hurt to have one, but it'll be gone pretty quickly once you start using it. With a plane or chisel you're pushing/pulling that tool at only X number of inches per second. Since you're the one powering the tool, you need a finely honed edge on the tool so it can work as effeciently and cleanly as possible.

[Cliff Rohrabacher]

If it works and you are happy with the result then you are golden.

That's it.

You can take an edge to a half micron diamond and then even further with less aggressive abrasives, and in fact, the edge is pretty nice. Cuts like who dun it.
I have a diamond glass plate system and leather strops I can and do use to produce mirror finish edges way far better than the average commercial razor.
But I don't do that every time. I do it when it matters to me.
And the hell of it is that the most famous furniture makers probably didn't have that kind of edge generation capacity. They had skills that were universally applicable and the vision & good taste to know what would be beautiful and timeless.

It's not the tool, it's the hand wielding it.

[Richard Wagner]

FWIW, I use my thumbnail at a 45 and set the edge on it, if it doesn't slip on the nail its sharp, and I never waste time polishing the rest of the chisel, just hone the cutting edge its all the does the cutting after all.

The other sharpness test I use is to pare the end grain of a piece of old oak, If I can make a shaving its sharp.

I have tried this with some success on soft wood but not so very good with oak or maple. I get some shaving action but it produces soming more like saw dust than shavings.

That having been said, my chisels are all better than they were. Well, except for one which I let get too hot. I was starting to acquire that mirror effect and got impatient (too long on the wheel).

[David Keller NC]

"They sure are pretty but are they really anymore functional, as a chisel, than what I have been using for years?"

I think you already know the answer to this, but "absolutely". A really sharp chisel will significantly reduce the amount of force required to take a shaving, and the cut will be far cleaner. The cleanliness of the cut doesn't matter all that much on the interior of a joint like a M&T or a dovetail, but it matters a lot when you're using the chisel to trim off a dowel that will be visible, or flush up a breadboard end.


"I have tried this with some success on soft wood but not so very good with oak or maple. I get some shaving action but it produces soming more like saw dust than shavings."[quote]

Theoretically, you should be able to get actual shavings from the end grain of most any wood if the chisel's sharp enough and the bevel angle is low enough (below about 30 degrees). But oak is sometimes difficult to to do this with because the large pores allow the shavings to break apart when they ride up the bevel of the chisel.

The key test is eastern white pine. This wood is extraordinarily sensitive to the sharpness of the edge. If you can peel a shaving off of the end grain of this wood, your chisel is about as sharp as it's possible to get it. And please, please, do not test your blades by trying to shave with it. It's downright dangerous - a moment's inattention can shave off a frighteningly large patch of skin, and might even require a trip to the emergency room.

[quote]That having been said, my chisels are all better than they were. Well, except for one which I let get too hot. I was starting to acquire that mirror effect and got impatient (too long on the wheel).

You can fix this, by the way, but you must grind off past the point where the chisel was blued. Obviously, you have to do this without further heating the edge past the temper point. This is one reason that a lot of us use a powered system like the Worksharp, Tormek, or dry grinding wheel for coarse grinding and shaping, and finish up on fine honing stones, ceramic micro-grit sandpaper, or leather strops with honing compound. That really fine edge that you're trying to achieve is very, very easy to heat beyond the tempering point on a powered system.

[Jim Koepke]

If it works and you are happy with the result then you are golden.

That's it.

You can take an edge to a half micron diamond and then even further with less aggressive abrasives, and in fact, the edge is pretty nice. Cuts like who dun it.
I have a diamond glass plate system and leather strops I can and do use to produce mirror finish edges way far better than the average commercial razor.
But I don't do that every time. I do it when it matters to me.
And the hell of it is that the most famous furniture makers probably didn't have that kind of edge generation capacity. They had skills that were universally applicable and the vision & good taste to know what would be beautiful and timeless.

It's not the tool, it's the hand wielding it.

That's good advice, as is what preceded it.

You will find as you sharpen blades and learn more about sharpening, your blades will become sharper. Seems to happen to just about everyone who keeps on sharpening.

There are a lot of different ways to get to a sharp edge. Each method has its advantages and problems. What works great for me might be a big mess for you.

Many like a hollow grind. There isn't a grinding wheel currently set up in my shop, maybe someday.

Some like micro bevels, not my style.

Some will insist you have to get a burr or wire edge. This bugged me for a long time until I understood how a burr develops and why my method of not dragging the blade will not make as much of a burr as one would get with the scary sharp method.

I think everyone will agree though that as soon as you start using a blade, it starts to dull. That is why some like to strop after every few cuts and why others will touch up the blades on their fine stones often.

David Keller NC says:

And please, please, do not test your blades by trying to shave with it. It's downright dangerous - a moment's inattention can shave off a frighteningly large patch of skin, and might even require a trip to the emergency room.

My thoughts on this are that a moment's inattention in the shop around sharp tools can get a person a trip to the emergency room whether or not they are trying to shave arm hairs. PAY ATTENTION!!!

I used to shave with a straight razor at times. It has crossed my mind to try a plane blade on my face when I want to take off a winter's worth of growth. If one comes along cheap, maybe another straight razor is in order.

Then again, it is often my practice to shave hair with my blades to test their sharpness. There is a four step grading system for this:

1 = getting there) Scrapes skin or goes over hair, may cut one or two hairs.

2 = close) Cuts a few hairs, can feel each hair being cut.

3 = pretty good) Cuts hair, can still feel some of the hairs catching on the edge.

4 = sharp) Cuts all hair in its path, you do not feel hair being cut and you think it might not be cutting until you notice the hair balling up on top of the blade.

After this, the blade could be stropped if you like. I usually do not strop, but do at times for some tools.

jim

[David Keller NC]

Jim - The reason I said this is two-fold. The first reason is that safety isn't a function of whether someone is good enough with a particular technique to avoid injury, it's the probability of the outcome, the frequency of the task, and the consequences of the outcome. There are many individuals that are conscientious enough to avoid amputating a finger from free-hand pushing a board through a table saw, but it still falls under the category of "dangerous" and isn't to be recommended on a net forum because there's a lot of folks that can't do it.

The second reason is that it's completely, totally, and irrevocably unnecessary - paring end-grain with a blade to test the sharpness is more than adequate for a test, so if there's no reason to put yourself in harm's way, even if the probability is low, then we shouldn't recommend it. And believe me, I've seen the ugly consequences of a newbie trying to test a very sharp blade by trying to shave arm hairs with it - they took a patch of skin off that was a good 2" wide and about an inch long. It bled profusely, and the victim confirmed that it was very painful.

[Jim Koepke]

Jim - The reason I said this is two-fold. The first reason is that safety isn't a function of whether someone is good enough with a particular technique to avoid injury, it's the probability of the outcome, the frequency of the task, and the consequences of the outcome. There are many individuals that are conscientious enough to avoid amputating a finger from free-hand pushing a board through a table saw, but it still falls under the category of "dangerous" and isn't to be recommended on a net forum because there's a lot of folks that can't do it.

The second reason is that it's completely, totally, and irrevocably unnecessary - paring end-grain with a blade to test the sharpness is more than adequate for a test, so if there's no reason to put yourself in harm's way, even if the probability is low, then we shouldn't recommend it. And believe me, I've seen the ugly consequences of a newbie trying to test a very sharp blade by trying to shave arm hairs with it - they took a patch of skin off that was a good 2" wide and about an inch long. It bled profusely, and the victim confirmed that it was very painful.

In the front of every issue of Fine Woodworking magazine is a statement that starts out, "Working wood is inherently dangerous. ..."

Shaving with a straight razor is inherently dangerous.

To move from where my tools are sharpened to where a blade could be tried on some end grain would be about 10 yards round trip. For me it works. For others it may not. Everyone's milage will vary.

To lift a patch of skin 2" wide by about an inch long would require me to be quite intoxicated to not stop before getting that far. My days of getting that intoxicated are far behind me and my shop is off limits if more than a beer or two has been consumed.

As is often said, what works for one may not work for another. How blades work on the material they are made to cut is the results that matter. Often my blades are sharpened in batches. The work to mount a dozen blades in different planes may beyond the effort I want to take at the time.

So forgive me my ways, but it works for me. I avoid cuts as much as possible, but I have not cut myself while sharpening and testing blades. Most often, it has been from clearing chips from a plane's mouth.

BTW, my experience has found that a dull blade is more likely to snag and remove skin than a sharp blade.

jim

[Richard Wagner]

Thank you for the guidance provided.

I know my blades are sharper than they have been. I can tell that by using them for their intended purposes. I am sorta looking forward to a project where I can really put them to work.

I tried shaving some hair but wasn't too successful. Technique I guess. I'll not practice to get this one right; at least not now.

I polished the back side of one chisels. Don't think I'll do that on all of them; at least not until; I find a situation where I think it'll make a difference. I did flatten the backs on all of the chisels.

Thanks again for your help. I know that this will improve my performace in the shop.