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Thread: Cambered iron for jointing Edges

  1. #1
    Join Date
    Sep 2009
    Cedar Rapids Iowa

    Cambered iron for jointing Edges

    Not too long ago there was a discussion as to whether to camber or not to camber when sharpening a smoothing plane iron. A couple of folks mentioned that a cambered iron was preferable for edges. While this seems counter-intutive to me, the comment came from a couple of respected posters. I am interested in understanding the mechanics - basically why is a cambered iron is best for edges?

    Kind Regards . . . Allen
    No, the sky is not falling - just chunks of it are.

  2. #2
    Join Date
    Apr 2007
    Fort Gordon, GA
    I don't know how well this picture is going to work. I found an email that I sent to a friend many years ago about this same topic and have tried to attach it - as trying to explain the benefits of the cambered blade is a bit tricky.

    I am a disciple of David Charlesworth. I had a very nice LN plane that sat around in a box for years until I watched the Charlesworth DVDs.... He, and many others, are more able to discuss the benefits of the cambered blade than I am. But I'll try to do my best....

    When I think of a face edge that needs to be jointed (and not always to match to another glue edge), I think of an uneven surface that has various high and low spots on it (looking at the bottom picture). A little high outta square here, a little low outta square there, etc, etc, etc. It is hard for me to understand how you can correct this error with a straight blade - or even with a fence. You'd have to almost "float" the plane above the wood, while holding it perfectly horizontal and square to the edge, to plane off the high spots. To me, that seems impossible. One method I think Paul Sellers (who I admire considerably) uses, is to apply greater pressure to the high spots. I suppose that seems reasonable to me - but again, how much pressure? How long do I apply it? How much? It seems like an error prone process... Match planing also is an alternative - but also has some limitations.

    A cambered blade makes the process easy, accurate, and repeatable. If you notice from the top picture, a cambered blade takes a thick shaving in the middle, and a thin shaving towards the outsides. That's pretty great, because if you think of a board that is out of square - that's just the kind of shaving you need to get it square. To remove a high spot - you need to take a thick shaving at that one spot to bring it down to the low spots that aren't touched (or minimally touched) by the outside of the blade (taking a very thin shaving). There is no need to apply greater pressure on the left side of the plane, then the right side, then the left - as you drive it down the board. Or trying to tilt the plane one way or the other. Or thinking that a thin flimsy fence is going to dictate to a very heavy #7 or #8 where square is. You plane naturally. The entire heft and sole of the plane is resting wholly on the edge of the board. You merely mark the high spots with a pencil (where the board isn't square), and "drive" the center of the plane along those high spots (as shown in the picture at the bottom). When you are pretty much square, you take one final shaving right down the middle to ensure that there are no high spots - and you have a perfectly square edge to the face.

    Again, I'd recommend David Charlesworth to you. It's almost something you have to try and do before it makes any sense. Here is another post that has a much better explanation and even pictures....

    To me, cambered blades on a jointer are crucial (and kinda makes me wonder while I bought a LA jointer during a LV sale while here in Afghanistan....).

    Clear as mud?

    - j

    - jbd in Denver

  3. #3
    I have always found the "lore of the cambered blade" amusing.

    A smoothing plane with a cambered blade may work, but will the concave surface it produces be superior to a dead flat one? Please draw yourself a diagram of two boards with concave edges facing each other. And then consider that, to create a perfectly symmetrical concave surface, the plane blade must be perfectly centered on the board over the entire length of the cut. Don't believe me, just draw a diagram and move the cut made by the cambered plane blade a few tenths to the left and right every few feet. Notice how any lateral movement off dead center changes the height of each edge, one side going a bit up, and the opposite edge going a bit down. Now consider two boards to be joined to each other, each edge tilting right and left in different directions and in different locations, with concave cuts of differing depths at differing locations. Can such a combinations of surfaces be made to bond when gluing up boards? Yes. With good glues and clamps, these inconsistencies are not overwhelming. But are they superior? No way.

    On the other hand, while a dead straight blade may create a tilted or twisted surface on the edge of a board if the man guiding the plane does not know how to shoot an edge properly, or if he has been drinking warm beer, a straight blade cannot create a concave surface, regardless of which section of the blade is doing the cutting. A straight blade eliminates several variables in the quest for precision. If you need pointers in shooting the edges of long boards (and no, you don't balance the plane on the edge of the vertical board, for Pete's sake), send me a private message.

    If you intend to simply finish plane the edge of a 3/4" thick board, a concave surface is no big deal. But what if the workpiece is the face of a door frame intended for a mortise and tenon joint? If the width of the face is 2" for instance, a cambered blade will end up cutting a bit of a hollow profile, one that does not improve the fit of rail to stile.

    The proper role of the cambered iron is planing wider surfaces where plane tracks are to be avoided. For everything else, and especially where the width of the material is less than the width of your plane's blade, a straight blade is quicker to sharpen, removes material more efficiently, yields the smoothest surface, and provides the highest degree of precision for joints.

    Never forget that your plane is the tool in your toolbox with the highest level of built-in precision. Don't cripple it by putting a cambered blade in it unless you actually need a concave surface.

    Don't misunderstand me: cambered blades have their place. Two of my very best hand forged blades are cambered. They are on my wide finish planes and are used for planing wide surfaces. Every other plane blade I own (not including rounds, hollows and molding planes, of course) is shaped as straight and square as I can make it, especially the blades in my jointer planes. The problem occurs when all your plane blades are cambered and you no longer have the tools to readily make a perfectly flat surface.

    Here is the important point: A good craftsman needs at least two finishing planes, one with a dead straight blade for precision surfaces, and another plane with a cambered blade for finishing and cleaning up surfaces wider than the width of the blade.

    Guys over here who are really into planing have special finishing planes with extremely wide blades so that the entire width of a post can be finished in a single stroke, avoiding steps, and the disadvantages of a cambered blade. This has been going on for at least 250 years. See the youtube vid below. Note that the blade is NOT cambered.

    I have never used an ouganna like these. Besides being horribly expensive blades, they are insanely difficult to sharpen. And just imagine what a change in humidity does to the block. Not practical. Kinda like benchrest shooting.
    Last edited by Stanley Covington; 02-04-2013 at 3:47 AM.

  4. #4
    Join Date
    Feb 2010
    Philadelphia, PA
    Because a cambered blade takes a cut the it heavier in the center than on the edge it makes it very easy to correct an out of square edge. You simply center the plane blade (where the cut is deepest) on the high edge. Because it is taking a very slightly heavier cut there it will bring that high edge down a few thou at a time. If the edge has some twist (out of square one direction on on end and out of square the other way 0n the other) its easy to adjust where the center of the plane blade is on board as you move through the stroke. Just center the blade where ever the edge is high until you've got it square... easy pessey

    Where camber becomes and issue is if you are jointing wide boards or match planing two boards together. Here a straight blade is preferred. The ideal solution (as I believe the historical solution in western woodworking) is to have two long planes. The first would be a trying plane. This plane is used for "trying" surfaces... as in making them flat and square and would have a cambered blade that allow you to more easily work wide faces and also use the camber to bring edges into square. The second would be the slightly longer plane with a blade honed straight across. This is what would historically be called a jointer. It is used for getting perfectly flat straight surfaces on long edges only, and in essence is actually a joinery plane as it is used mostly in match planing two boards to be edge glued.

    I don't know a lot about historical specifcs, and truth be told I think everything I just said came from a Bob Rozieski's (sp) website. What I do know if that I really like having my No. 6 setup with camber to do most of my flattening and to bring edges into square and also having my old no. 8 setup with a stright blade for match planes and jointing edges that are longer or wider than I normally do.

    I think this is the video where Bob covers this stuff:

    EDIT: Suppose I should have read Johns post in its entirety before, seeing as how I basically repeated what he said but less eloquently . So yeah, what John said....
    Last edited by Chris Griggs; 02-04-2013 at 6:35 AM.
    Woodworking is terrific for keeping in shape, but it's also a deadly serious killing system...

  5. #5
    Join Date
    Sep 2007
    Longview WA
    Just another example of there being more than one way to do something.

    Many years ago one of the magazines had a suggestion that a jointer be positioned for work by setting it with one edge of the toe and the opposite edge of the heel aligned on the board to slightly lower the angle of the blade. Another suggested working the plane side to side to even out the wear on the blade.

    Somehow or some way all of these methods have worked for some over the years.

    For me, a cambered edge on a plane's blade is only used on a few planes. For some folks a varying amount of camber seems to work on everyone of their planes. Can everyone be right? Of course they can all be right. This is an art, craft, hobby of individualistic souls. With so many ways to get the project done, it is best to experiment and find the way that works best for your needs in your shop in your hands.

    If you are using Stanley planes or other equivalents buy a few cheap replacement blades. The 2" Buck Brothers blade at Home Depot is only $3. Get a few and give them different amounts of camber. If you find one that gives you a case of the warm fuzzies, then you can use that on a premium blade and find satisfaction in the shop. Let me tell you, it feels good.

    For smoothers, my blades are not cambered. When taking a heavy cut they will leave tracks. With a sharp blade taking the thinest shaving possible, there are not any tracks. If a high spot is felt on a surface, setting the plane on it and taking a shaving will only effect the high area. The same blade that takes a full width shaving having one only a 1/4" to an inch coming out the first time will make you wonder what's happening.

    With a longer plane and lots of use one will likely be able to "sense" square as they are working. "Trust but verify," as someone once said. If my wood working has been on hold for awhile, an edge may end up high on one side. This is where being able to judge the thickness of a shaving and how out of square an edge may be comes in handy. If my shavings are about 0.005" and the edge is out about 0.010" then the plane is tilted very lightly to take a shaving about a half thickness of the edge. This should get the edge to square in two strokes.

    This seem to work for me. It may not work for others.

    The object of our endeavors is to find enjoyment, make money, to make a few things for around the house or family and friends. My finding has been that the less time spent wracking my brain around all the best ways to do something with so many ways to be done does not bring as much enjoyment as going out to the shop to "just do it" as someone else said.

    Last edited by Jim Koepke; 02-04-2013 at 12:40 PM. Reason: spelling
    "A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty."
    - Sir Winston Churchill (1874-1965)

  6. #6
    I don't think it makes much of a difference either way. experience with gluing edges, how much pressure it takes to do it and how flat the results are should dictate what you prefer, with the exception being a straight across blade for match planing.

    On very thin boards, you're probably going to have to shoot the long grain, anyway.

  7. #7
    Join Date
    Sep 2009
    Cedar Rapids Iowa
    Thanks for all the info guys. THe Japanese plaining videos make me wanty to either seel all my western planes and go for Japanese planes - or m,ore likley just get pout of the hand plaing altogether and go back to power sanding and out of this neanterhal vortex of money pain and some pleasure . . . .
    No, the sky is not falling - just chunks of it are.

  8. #8
    This is an interesting discussion. Indeed, there are many ways to get the job done, and most methods will achieve the desired results.

    I attended a forum of the Iron and Steel Institute of Japan (に本鉄鋼協会) last week. An eccentric group of people attended the forum, including Professors, anthropologists, employees of the big steel makers in Japan, blacksmiths, museum managers, bicycle mechanics and a housewife or two. The subject of the forum was "Iron, One Man, Tools, and Technique." Surprisingly, I was the only general contractor. Three speakers spoke. Mr Asaoka’s presentation was titled: "Modern History of Metals From the Perspective of making a Living." Professor Kawashima made a presentation on his studies of Irish tools and traditions as preserved in the Ulster Folk and Transport Museum. I learned much about the development of the shovel in the various counties of the Emerald Isles. Mrs. Katsuki spoke on the shift from the use by blacksmiths of Japanese native steel (tamahagane) to imported steel. Some of it was deadly dull, some was fascinating.

    When the subject of tamahagame came up, a swordsmith in the audience (always eager to promote his work, I am told) added his opinions on the differences between the two materials. He began his lengthy comments by asserting that he was not a true "craftsman" (shokunin 職人)because he only managed to produce two satisfactory swords a year while a true craftsman was required to be both quick and precise. The keywords I want to draw your attention to are Quick, and Precise. These words are important because, given enough time, most people can achieve precise results using most even bad tools and techniques. But a true Craftsman or artisan has refined his tools and techniques and movements and eyeball to achieve high precision quickly.

    The word shokunin or craftsman or artisan in Japan means a lot. Such people, while seldom well compensated, are very respected, and allowances are made for their perceived stubbornness and curmudgeonly behavior. A true shokunin can do amazing work in very little time. No wasted movement or "sneaking up" on lines.

    I don't pretend to be a shokunin, but I have spent a lot of time around, and learned a lot, from them. At first, I was offended when they insisted that things had to be done a certain way, because, like the country boy that knows how to shoot but has to be retrained to shoot properly when he joins the Marine Corps, I had learned how to use tools from my father and uncles (professional carpenters and cabinetmakers) in ways that, while good, were not good enough to achieve the quality or productivity required to get the job done properly per the standards of these shokunin. So in Japan I relearned how to sharpen a blade, use chisels and planes precisely, cut fast and straight with a saw, layout with ink and line and knife and gage. And I compared my productivity and quality before and after and realized the improvements were huge. In some details, I disagree that the ways I was taught in Japan are better than the way I learned from my Dad and Uncles in America. But in most ways, they are far superior. I know this because I have learned both ways and compared the results side by side using Mark-1 Eyeball, precision straightedges, machinists squares, micrometers and stopwatches. I kept records, so I know it is not my imagination or a "fragment of an underdone potato." I urge anyone that reads these words to try different ways and compare the results in the same way.

    This will not take the joy out of woodworking as a hobby, but will make it more interesting as the years go by and you develop confidence in your skills because you have actually tested and compared techniques and know which ones work best for you.

    Woodworking as a hobby has really taken off, but with the death of the master/apprentice system, there is a huge dearth of truly skilled teachers. Most people are nowadays self taught relying on books and magazines often written by people trying to sell tools or promote themselves. In fact, the guys writing the magazines and books are, for the most part, self taught too and are more confused than the reader. Notice how what they write and promote and push changes from year to year, publication to publication, and even issue to issue. And then there is the financial conflict of interest. There is always more pressure to buy buy buy.

    Amid this confusion, I urge you to first get a bound notebook (not a scrap of paper that will get lost). This will remain in your workshop or toolbox until you are too blind or feeble to use your tools, so get a decent one that will last. Then get your hands on a truly accurate machinists square, straightedge, dial caliper, micrometer and feeler gages. Sorry, these can be expensive, but they are absolutely essential and will last longer than you, and once you own them, they become the standard against which you can check other tools and work product for precision. These tools should NOT be made in India or China. If you wonder why, compare a truly precision machinists square or straightedge or dial caliper or micrometer or feeler gage against an Indian or Chinese tool. Scary. A combination square, even if it is made by Starrett, is not good enough. Buy from a serious industrial machinists supply house, not a woodworking tool retailer. Such professional tools will have a certificate of accuracy measured in ten-thousandths of inches, and a no bullshit guarantee.

    Next, analyze and break down your woodworking into discrete, individual operations (i.e. cutting a tenon shoulder, or planing the six sides of a board flat and smooth and square, or chopping dovetails, etc., etc.). Write these in a table in your notebook, allowing enough space for each operation to have several dedicated pages all its own. Then perform each operation on standard test pieces (same species and dimensions) to the best of your ability using the tools you own. Measure and record the results using your machinists tools and a digital stopwatch (you probably already own a wristwatch with this function). Don't forget the date and time and tool. These records will become YOUR standards for accuracy and quality and speed. Now you truly know what you can achieve using one tool or technique to perform a particular operation. Then compare new methods and tools in performing the same operation. Record the new results. Determine if there really is an improvement or not.

    As a result of your diligence, over time, you will see your skill and quality and speed improve. You will be less easily frustrated as you make fewer mistakes and waste less material. You will use fewer tools. You will buy fewer woodworking magazines and fewer tools. Your bullshit meter will become finely calibrated. Your shoes will wear out quicker while your back hurts less.

    A word to the wise.
    Last edited by Stanley Covington; 02-04-2013 at 9:09 PM.

  9. #9

    I love Japanese planes, but they can cause a new guy great frustration. I recommend you learn Western planes first, then try Japanese planes when you have the skills required to appreciate the sharpness and other advantages.


  10. #10
    Join Date
    Mar 2009
    Chevy Chase, Maryland
    Stan, what is it that you make? Do you have a web site or pics posted online anywhere? I'm curious what you are making that you have need for such exacting precision that only "serious industrial machinists supply house" squares will suffice. I'm not trying to be a smart ass. I wll admit, that I'm drawn to more free and slightly less exacting woodworking. Nothing shoddy or weak (qyuite the opposite in fact), but more "folk" sort of handwrought pieces appeal to me - perhaps it is only because I'm incapable of meticulous perfection? I guess in Japanese terms, I'm more drawn to aesthetics like wabi-sabi. What's your bliss?

  11. #11

    I don't have a website or pics online. I always forget to take pictures. In the case of commercial projects, some Owners get really upset if they see pictures of their stuff taken by someone else, so I tend to not take pictures.

    Right now, I'm not doing any woodworking at all, just bidding commercial construction projects.

    Recall that the precision measuring tools I mentioned in my previous post are primarily intended to check the precision of tools and test pieces. The precision of the projects I have undertook in the past did not require precision measuring equipment, nor did I use them in day to day work. Like you, I'm sure, I don't even use measuring devices or dial calipers for measuring most components, but use layout sticks for smaller projects such as cabinets and furniture. I have no doubt that you can work to very precise tolerances when you want to.

    While I recommend that every woodworker have such tools, and especially the beginner trying to develop his skills, I seldom use them to check my own work anymore.

    I believe that a woodworker needs a set of high-quality precision tools primarily to check the accuracy of the measuring and layout tools he uses everyday. As you know, everyday tools wear out (marking knife shaves a square) or become damaged (a dropped straightedge), and without a truly reliable reference tool, it is difficult (but not impossible) to ascertain a problem. For instance, I ordered a Starrett combination square last year when I lived on Guam. Not a cheap tool. When it arrived, I checked it with my machinists square. It was way off. My feeler gauge told me it was out of square by 0.012" across the beam. Unthinkable, right? Of course, when I contacted the retailer, he said that Starrett tools were carefully checked before they left the factory and that he had never had a problem. I returned it to the retailer, and he followed my instructions on how to check the accuracy (he checked it against the Incra tool you like, BTW) saw the problem, and sent a replacement with his apologies and a baseball cap. But if I had blithely assumed the square was accurate, just because all my other Starrett tools are dead accurate, the accumulation of errors (which Murphy says accumulate and do not cancel each other out) caused by that tool would have caused me serious grief when making a cabinet and drawers. I'm not running down Starrett tools, I'm just saying everything made by man has problems at one time or another.

    Another example. I bought a L-N Jointer plane when they first came out when I was living in Columbus, OH. L-N tools I had purchased earlier had been very precise, so I assumed the jointer would be too. Guess what? It would not cut a flat surface. A check with my straightedge, a hardened steel precision ground tool I know is accurate, showed me the sole was not only curved, it was twisted. Easily fixed with time and elbow grease, but without an absolutely reliable straightedge and machinists square, it would have been more difficult to identify and repair.

    I likewise have a high-precision dial caliper besides the everyday one I have had to replace several times over the years (the damned things seem to grow legs and run away).

    I occasionally check my everyday tools this way, then put my precision measuring tools back in their boxes.

    I am very fond of wabi sabi stuff, Sean, and prefer simple designs with little decoration. Evidence of hand work and visible joints in the finished piece is pleasant to me, despite David Weaver's distaste for end grain porn. I like to see the structure of things, whether it be furniture or buildings.

    When I made furniture and cabinets for a living, customers would sometimes ask for fancy designs and complicated moldings and carvings. I once did a commission for a wealthy Filipino lady that included 35 shoji screens, some in black walnut and some in cherry. She wanted complicated kumiko zaiku (asa-no-ha and other designs of intersecting small pieces) and carved waist panels of birds and flowers. More Chinese than Japanese, really. The front door I built for her house in the new entry I also built was 3" thick Honduras Mahogany with life-size full relief carvings of jungle orchids designed by an artist. It was bizzare, and ridiculously fragile, but that was what she wanted so that is what she got. Not my taste.

    If you like, I can take some pictures of the few pieces I brought with me to Japan and post those. In fact, my wife is supposed to meet me at Yodobashi Camera after work today to help her buy a new camera, so it would be good way to figure out how to use the new toy. What do you think of the Nikon D5200?

    I have seen the pictures of your stuff on the web and admired the lines and details.


  12. #12
    Quote Originally Posted by Stanley Covington View Post
    Evidence of hand work and visible joints in the finished piece is pleasant to me, despite David Weaver's distaste for end grain porn.
    Maybe it's just a phase (for me), I hope my comments about it don't offend anyone.

    I think it's a product of overexposure to visible dovetails and finger joints.

  13. It's not just you. A lot of the conspicuously exposed stuff today has the aroma of freshly baked dovetailer proving to the world he or she can cut the joint. All of a sudden they become appropriate *EVERYWHERE* and in all of their dizzying variations too.

    Krenov often used dowel joinery for carcases rather than disrupt the flow of grain and clean look of the side of one of his cabinets. I like that. He could cut dovetails, it goes without saying. He didn't need to prove it time after time by featuring them time after time. Here was a designer/craftsman in full bloom making informed and in the end restrained and tasteful artistic choices rather than flavor of the week stuff we so often see these days.

    I can't remember which of his books it is by title but in one particular volume his section on dowel joinery was as long, if not longer, than any other topical section in the book. Design coming first is the hallmark of a mature cabinetmaker, in-your-face dovetailing of everything in sight is not, nor is overwrought/overengineered joinery. That's what people do who have no real artistic vision, or who are forced to adhere to a stifling and rigorous tradition that demands absolute and unerring virtuosity of very complex joinery at the expense of all else. How terribly unappealing from my point of view.

    Craftsmanship is not art. It's a wonderful thing but it is not art. Fine craftsmanship is the highest and best calling for most of us, but we don't need to lose sight of what it is and what it is not.
    Last edited by Charlie Stanford; 02-05-2013 at 12:32 PM.

  14. #14
    Join Date
    Mar 2009
    Chevy Chase, Maryland
    Thanks for the detailed and thoughtful answer. I certainly have seen work that is intricate with watch-like fits. I was imagining maybe you worked in some style like that. I'm afraid that as a hobbiest, with only handfuls of hours a week in my shop, I will forever be like the swordmaker you describe putting out two a year. I'm undisciplined in that I would rather put out two a year than use half my shop time training on techniques so that in ten years I might be able to put out three!

    Speaking of delicate, I tried something new for a stretcher on a little side table I currently have in progress. I was thinking of saw handles and hepplewhite chair backs, and wondered if the short grain would be strong enough in this sort of application. I think with some luck, it may last 50 years, but not 300 (my usual aim ;-)). It's more than strong enough for its use and typical handling, but over time, most any furniture will face some rough handling. If I did it again, I'd use some joinery to avoid any short grain.

  15. Gorgeous. Precise enough for me! FWIW.

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