A micro back-bevel on chisels? Why not?

[David Dundas]

As a member of the species Homo sapiens (subsp. dominoensis), I very rarely venture into Neanderthal territory. However, today I have come to receive enlightenment about an edict issued by a prominent Neanderthal Elder, David Charlesworth. On page 33 of Volume 1 of his book 'Furniture-making Techniques', he states, without giving reasons, that his "ruler trick", which I use all the time for producing a micro back-bevel on plane irons, "must never be used for chisels".

In fact, I use a slight modification of his ruler trick for chisels - I lower the back-bevel's angle to only about 1/3° by resting a point on the back of the chisel about 3" (rather than the 1 1/2" that he recommends for plane irons) from the chisel's edge on the ruler while honing a short (about 1/16" long) back-bevel on the chisel. According to my trigonometry, this ensures that the resultant edge of the chisel is displaced from the plane of the back of the chisel by only about 4/1000ths of an inch. In my view this causes no perceptible detriment to the performance of the chisel. But it certainly speeds up the sharpening process immensely.

So, can a Neanderthal guru tell me what, if anything, is wrong with my ignoring the Charlesworth Edict?

David

[Ryan Cathey]

It's to help with chiseling to a line because with the back bevel when you drive the chisel down it acts as a wedge against the line that compresses the wood fibers and makes for a sloppy joint.

-Ryan C.

[Mike K Wenzloff]

I dunno if that Charlesworth fella is worth listening to...

OK...he is worth listening to. But little to none of this is new info as regards micro or back bevels. Including not doing them on chisels.

Reason is like Ryan states. Point being that the chisel will drift away form a line when you don't want it to, nor is it as useful for paring operations regardless of how little a micro bevel you put on a chisel.

A swipe or two with the chisel flat on your sharpening medium when done with the bevel is all it takes as regards "sharpening process."

Take care, Mike

[David Dundas]

Ryan,

I see your point about the wedge effect, but I contend that, with a tiny, very low-angle back-bevel, such as I use, the effect is negligible, since the wedge is so small.

Mike,

I do not agree that flattening the back of the chisel just takes a couple of swipes on the sharpening medium. The backs of chisels made from A2 tool steel may take an hour or more to flatten and polish to a mirror finish, particularly if, like the Two Cherries brand, they have been polished by a tumbling process that rounds their faces. I have spent at least an hour trying to flatten the back of each of my Two Cherries chisels, and am nowhere near getting the mirror finish at the chisel's edge, the only area where it matters. It is easier to do with chisels made from softer steel, but is still a long process.

David

[Mike K Wenzloff]

Ah, well David...see you didn't write "flattening the back of the chisel," but what I quoted re "sharpening process." Which I would contend are different beasts. Once flattened--and I would also contend don't need to be flat to the nth degree--the "sharpening process" is but a few swipes.

fwiw, I have never spent longer than 5 to 10 minutes flattening a back of a chisel. Even TC chisels. It can be a relatively quick process if one is willing to burn a few electrons. And while I have certainly polished customer chisels to 8k grit, I do not do so with my own chisels immediately.

After flattening, I use a 1k stone and on to a 2k. When sharpening thereafter the back is swiped on an 8k to rid the wire edge.

Take care, Mike

[Larry Williams]

Ryan,

.... I contend that, with a tiny, very low-angle back-bevel, such as I use, the effect is negligible, since the wedge is so small.

I don't really think of a 1/16" "back-beve"l being small, even on a plane iron. My question is how big is this going to be after a couple sharpenings? Given that you have to maintain this "back-bevel" it will grow with each sharpening. Remember the ultimate quality of the edge depends on the condition of both surfaces that create that edge.

At some point, it looks to me like you'll be facing serious grinding to get rid of a growing problem. I don't like sandpaper sharpening because dubbing of the edge is inevitable. I think the reason Charlesworth came up with his "ruler trick" was to quickly get students' tools functioning in workshops by overcoming poor sharpening and edge dubbing. The ruler allows him to basically dub the edge at a steeper angle. It looks like a Band-Aid technique to me and doesn't even address the real problem, a student who hasn't learned to sharpen. If a student hasn't learned to hone, my bet is they haven't learned to grind either. Soon that student will have to both grind and flatten the iron but Charlesworth won't be around to help them. I think he's leaving them with a time bomb when he should just take the time to teach proper sharpening.

He has people now taking new basically optically flat irons from LV and LN and intentionally dubbing them from the start. A flat back is easier to maintain once you've got it than messing around with a ruler on a stone. Starting out by messing up a flat back seems a little backward to me.

I'd rather flatten a new 3/16" thick 2" wide plane iron that grind 1/8" off the edge and regrind the bevel but then I've not flattened a TC chisel. Maybe I should have started by asking what you're using to flatten chisels?

[Andrew Williams]

if you put a back bevel on your bench chisel it becomes a carving chisel. a bench chisel should have a flat reference surface, like a bodiless plane. with a back bevel you would never be able to pare a straight flat surface.

[Alice Frampton]

David,

IIRC, if you follow Mr Charlesworth's technique you'll not actually side-step the flattening of the back at all. IIRC, and I haven't checked to refresh my memory, he still requires that the back of the iron be flat and the "ruler trick" is only employed at the polishing stage.

Cheers, Alf

[David Dundas]

Alf/Alice,

I am not wanting to avoid flattening the back of the chisel altogether; I am suggesting that, once the back is more or less flattened with perhaps an hour's work on a coarse and then a fine diamond stone, it is OK to form a very small, very low-angle back-bevel on a chisel, so as to be able to quickly achieve a mirror finish (by honing, using the 'ruler trick' with Veritas honing compound rubbed on a waxed piece of MDF) on the crucial small area of the back of the chisel immediately adjacent to the edge.

David

[Robert Rozaieski]

So, can a Neanderthal guru tell me what, if anything, is wrong with my ignoring the Charlesworth Edict?

David

David,
I'm no guru, just a wanna be who likes to use and experiment with tools. Like you, I challenged the "traditional" knowledge that chisel backs must be absolutely flat. I hear what folks say about a flat reference, blah, blah, blah, however, carvers can create flat surfaces in relieve carvings with double bevel chisels so why couldn't I pare a mortise or dovetail with a similar chisel?

I am currently trying "the ruler trick" for myself on some older firmers on which I did not want to spend the hours it would take to lap flat. It just doesn't make sense to me that pretty much all of the older chisels that we find in the wild are not flat enough for fine work. Those tools were good enough to make some awfully fine furniture before we got our hands on them. And 18th century woodworkers certainly didn't have float glass, mdf or granite surface plates to get a machinist flat back. I question whether they even wanted it.

I've only been experimenting for a short while with mine so take this with a grain of salt. To date, I notice very little difference between using my flat backed chisels and my "micro-bevel" backed chisels. The back bevel seems to actually help my paring because I can control the depth of the pare by changing my angle of attack similar to a carver. With a flat backed chisel, this is more difficult as the chisel wants to dive into the wood if you raise the back above the plane of the wood (which is why carvers put double bvevels on their tools).

Chopping seems to be little affected as well. Even a flat backed chisel will want to drive backward if you hold it vertically. The easiest line of travel for the chisel is the bisection of the bevel angle (as stated in a previous response, the edge of a chisel is a wedge, flat back or not). The flat back of a chisel does not pevent this as it is still a wedge (if you think it does, chop a dovetail or mortise right on the baseline from the beginning of the chopping and see where your base line ends up). I use the same chopping technique as I do with flat backed chisels; start the chopping in from the baseline and clean up to the baseline after the joint has been cleaned out. This prevents excess undercutting.

I'm still experimenting as I don't think I've been using the setup long enough to make rock solid conclusions but so far, I like them. Initial setup of a new old chisel is certainly easier as I don't worry about hours of lapping. I'm certainly not going to give up my nice flat backed A.I. chisels but this is because I just like using them, not because I've found them to be that much better performers than my old firmers (we're not comparing edge retention here).

My advise is to try it for yourself. After you've used them for awhile, let us know what you find out. Maybe we can all learn something new.

[Bob Opsitos]

It just doesn't make sense to me that pretty much all of the older chisels that we find in the wild are not flat enough for fine work. Those tools were good enough to make some awfully fine furniture before we got our hands on them. And 18th century woodworkers certainly didn't have float glass, mdf or granite surface plates to get a machinist flat back. I question whether they even wanted it.


Sounds like we need Coke v Pepsi style double blind test for micro beveled chisel backs. :D I'm betting I couldn't tell the difference; simply don't think I have enough skill/experience to discern what I would think is a subtlety.

Another interesting comment that came to me, was the implied thought that most older tools found were in the hands of capable craftsman and the conditions of said tools reflect the skills of that craftsman and the fine furniture they created. I wonder "back in the day" what the range of skills were given that fewer people did woodworking as a hobby, i.e, impling that if you had the tools you had the skills.

I mean, 100 years in the future, should someone find my chisels in a barn, one might assume they were used to build fine furniture and their condition was indicitive of the necessary requirements to build fine furniture. This is not necessarily a truth, vs if you found Sam Maloof's chisels.

Not saying anything, as I've not see the condition of enough old chisels to even make an intelligent comment of the requirements of those conditions and furniture quality. Consider it more of a curious thought.

That all said, I lap the he!! out of my chisels till their pretty damn flat and shiny, at least at the front. I like the shiny bits.

Thanks
Bob

[Robert Rozaieski]

Another interesting comment that came to me, was the implied thought that most older tools found were in the hands of capable craftsman and the conditions of said tools reflect the skills of that craftsman and the fine furniture they created. I wonder "back in the day" what the range of skills were given that fewer people did woodworking as a hobby, i.e, impling that if you had the tools you had the skills.

That is a good point and I certainly did not mean to imply that just because someone owned the tools that they were a fine craftsman. The opposite is typically true of the old tools we find, of which many seem to be of the paint can opener variety:mad:. The problem though is that most chisels we see today on the old tools market are from the late 19th century up to the mid 20th century. During these periods, hand tool skills were being lost to machines so it's difficult to know what the user's skill level was with those tools (could have been a farmer using the tools to fix their equipment).

The point I was trying to make though is that I've never once heard someone gloat "hey I found this old chisel and the back was nice and flat". In fact, usually the opposite is true and it takes hours to flatten them. It just doesn't make sense to me that it should take so long to flatten the backs of these chisels if it has always been common knowledge that a chisel back needs to be flat to perform it's task. If this were so, wouldn't all the old knowledgable craftsmen have done it? I would think that at least some chisels found in the wild would have flat backs, no? I've never heard of anyone finding one though. This begs the question, was it necessary then and therefore is it necessary now?

My opinion is that the only way to know for yourself is to experiment ;)!

Bob
Stirring the pot :D

[Harry Goodwin]

Well, Larry and I have like opinions whatever they are worth. Most old furniture made with hand tools was done during the flat era on chisels and plane irons and has worked for generations. If I do the rule trick on my L&N's they will take a week to reflatten them and maybe in my view never the same. Using a stone that is courser will help that first flattening experience. Harry

[Derek Cohen]

David

Welcome to the Sawmill Creek forum. I do not recall seeing you here before (for all, we are old mates back in Oz).

I have also wondered why we make such a fuss about a miniscule amount of steel at the back of the chisel blade. And I have no doubt that a chisel with a minute backbevel could be made to work. Hell, you can make anything work if you want! But the fact remains, if you have a backbevel, you will always have to be making an adjustement, no matter how small. Pare directly downward and, especially if the timber is hard, the back of the backbevel will push the chisel away from the wall. You may get away with it more easily in soft woods, but I really don't see the point. Grief, I had this conversation with you about three years ago!

The other issue that makes me very reluctant to use a backbevel - even on plane blades (unless they are old and very out of flat) is that I like to re-fresh my blades as I work by stropping them on a horse butt leather (or MDF) and green rouge. With a backbevel one cannot clean up the back of the bevel without angling the blade (I do this freehand) - and thus increasing the size of backbevel!

I suspect you are using the polished Two Cherries chisels. Damn, these should be outlawed as the backs are always dubbed - their cheaper unpolished versions are recommended. Here is my article on lapping the backs of blades:

http://www.wkfinetools.com/contrib/dCohen/z_art/lappingBlade/lappBlade1.asp

Note that blades only have to be smoothed at the very edge of the blade's back. The remainder of the back only needs to be flat.

Regards from Perth

Derek

[David Dundas]

Derek,

I was hoping I could slip this one past without your noticing it:) I remember your producing the same argument when I brought it up before, and I was not really convinced. However, I didn't get around, until recently, to working out by trigonometry by how much the edge of the blade is displaced from the plane of the chisel's back by a mini back-bevel of 1/3° 1.5 mm (1/16") long. Since that distance is only about 0.01 mm (4/1000"), as I mentioned above, I cannot believe that it makes a discernible difference - I certainly cannot detect it.

If I had realized that unpolished Two Cherries chisels were available, I would have bought them. As it was, I spent considerable time and effort flattening the backs of my two polished chisels. But it would have needed considerably more time and effort to get them to the state where the back was perfectly flat in the area adjacent to the edge. So I decided to go for the back-bevel. In fact, I don't often use chisels to chop to a line anyway; I usually use them for paring only; so I am primarily concerned to get them as sharp as possible with the least effort.

After buying the Two Cherries chisels, and being happy with the quality of their steel, but very unhappy with the amount of work needed to get them to a useable state, I decided to lash out and buy a LN chisel. I have been very happy with that.

Another advantage of the LN chisels is that their side faces are very narrow and a constant width, unlike the side faces of the Two Cherries, so that they can be gripped properly by the jaws of an Eclipse-style honing guide, which is unuseable with the Two Cherries. However, I now have a LV Mk 2 honing guide, so that doesn't now matter to me.

David

[Steve Hamlin]

:eek: Hey, no, nope, shush, I'm not listening, la lala la...

Please, NOBODY say chisels don't need to be flat! Don't even quote someone else saying it :mad: :D

Have just finished flattening the backs of mine - all this weekend, all last weekend, and then the start's lost somewhere deep in the mists of time, but I'm not sure the Iron Curtain had fallen...

But it's done, woohoo! Just gotta polish now, and then I can do stuff with wood again, phew!

I have a couple of paring chisels, neither of which I'd previously flattened properly, one with a very slightly raised edge (polished 'flat', but mucked up on wet'n'dry) and the other, less flat overall, but with 4" flat at the business end. The latter was far better at its job, but the rounded fulcrum in the middle of the blade was a pain with longer reaches.

I threw these into the bucket with some new ones for my lap fest. I figure most will outlast me, and will never need doing again, so a couple of weeks black fingernails, scuffed palms, no worries about anaemia and no wood, are well worth the trouble.

Guess it's averaged about 3 hours each blade. Worst were Ashley Iles - hard and concave, though really nice shallow sides. Sorbys proved harder, less consistently concave but overall flatter (and none convex overall, though nearly all with a 'dent' around the hardness test pimple). Henry Taylor had the widest variation, though softer, so not a big problem.

Cheers
Steve