Announcement

Collapse
No announcement yet.

Sharpening quiz for single edged tools

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Sharpening quiz for single edged tools

    In my youth, I was a

  • #2
    Re: Sharpening quiz for single edged tools

    To hold Edge


    Reduce Drag

    Comment


    • #3
      Re: Sharpening quiz for single edged tools

      2. Breaks the chip or forces the waste out of the cut.

      3. Acts as a fulcrum, or pivot.

      Al

      Comment


      • #4
        Re: Sharpening quiz for single edged tools

        except some of us prefer our knives flat ground lol............."diffrunt strokes fer diffrunt folks"!
        "Lif iz lik a box "o" choc lets, ya nevr kno whut yull git!"

        Comment


        • #5
          Re: Sharpening quiz for single edged tools

          Dave, that's just a veeery looooong bevel!

          Al

          Comment


          • #6
            Re: Sharpening quiz for single edged tools

            Lol...................
            "Lif iz lik a box "o" choc lets, ya nevr kno whut yull git!"

            Comment


            • #7
              Re: Sharpening quiz for single edged tools

              [quote=makinchips;161940]Can anyone guess what I've got in mind for the third thing?[quote]

              3) requires us to handle it more carefully than in it's pre-beveled state, or face unpleasant consequences.

              My thinking goes like this... if it were unbeveled on all sides, I'd have a flat piece of steel, something like a hinge hasp. I could grasp it firmly, throw it up and catch it, shove it in my pocket, drop it on the concrete floor, all without incident. When I grind a bevel on it, and the bevel plane intersects with the "back" plane to create a sharp edge, the question then becomes, how to balance the rising cost of gasoline with my sudden need to buy more Band-aids? The answer is, "Be careful, ya knucklehead! That thing is dang sharp."

              In addition, I now have a certain investment in the time and materials and mental engineering it took to grind the bevel, and I want to protect that investment. No longer will I smack it on the bench vise, use it to scrape old head gaskets, or pry open a paint can. Ever since it gained the newly sharp edge, it has become a more specialized tool, and infinitely more useful within the "cutting/slicing/parting of wood fibers" scope of it's new (narrower) function. It has evolved from a "found object", mass-produced by Stanley Hardware Co. and shipped in case-lot quantities to an unknown destination, to an "artifact", deliberately modified by me and put to my own (possibly nefarious, but more likely benign) uses.

              It provides an opportunity for me to develop new cutting/slicing skills, allowing more options for dealing with life's sometimes difficult situations than my previous scraping/whacking/prying skillset. I have quite possibly increased its value to others as well, in the sense that I may trade it for something I need, or use it to slice their tomatoes in exchange for a tomato for myself. Perhaps I should invest some additional time and materials in making a scabbard or guard of some kind: both to protect me from it, and to protect it (specifically its cutting edge) from the abuse I might otherwise accidentally inflict on it. Will this lead to further experimentation and/or skill development? Only the shop teacher knows for sure.

              You're right, Joe - this is kinda fun! See you on Sunday.

              Parker

              Comment


              • #8
                Re: Sharpening quiz for single edged tools

                Mr. Joe, Mr. Joe, I have a question. After thinking a little about it, and with apologies to the rest of the class, I'd like you to elaborate on answer #2. I've been fooling around with my single-edge tools all yesterday afternoon trying to understand how the bevel can guide the edge, and I just can't figure it.

                "2. The bevel guides the cutting edge.

                My thinking goes like this......if the edge could be removed from the tool, I'd have a very thin wire, very thin. The question then becomes, How to control this edge? The answer is the bevel. It rides on the wood, guiding the edge to cut or remove the wood. Something like a hand plane....the bottom of the plane guides the cutting edge. In this case, straight and flat."

                I'm assuming that you mean single-bevel tools such as bench chisels, plane irons, and technically including Dave's flat ground knife. (On mine, the edge is firmly attached to the body of the tool, and I've never found a reliable way of removing it intact to produce a very thin wire, so I have to conduct my experiments with the edge still attached.) Also, I don't hollow-grind my tools, so the bevel is flat (planar), not curved.

                Let's start off with a bench chisel, if you don't mind - the one I'm holding is an old 3/4" Fuller, with a straight bevel of about 1/4" long, edge honed quite sharp at 25 degrees for softwoods. I also have here a 16" chunk of fir 1x4, in which I'd like to carve a groove, say, 1/8" deep. I place the chisel tip on the wood bevel down, and adjusting its contact angle so the bevel surface is exactly parallel to the wood, 25 degrees, I push it forward. When the bevel rides the wood, i.e. 25 degrees or any lower angle, no cutting takes place because the edge is at or above the wood surface. Only when I lift the heel of the bevel above 25 degrees does the cutting edge bite and start cutting, but the bevel is no longer riding the wood. The tip is cutting and the heel is floating along somewhere above the wood surface. It's kinda hard to take an even shaving thickness because 1) I'm applying the forward pressure at the handle, which wants to lift, which makes the tip dive deeper into the wood, and 2) the 1/4" bevel of the chisel is a rather small reference plane, and it's too easy to over- or under-incline it. I seem to get better results when I flip the chisel to a bevel-up position, and as you observe, the forward component of the force exceeds the downward component. In the bevel-up position, I don't see the bevel doing anything but guiding the chip, as Al mentioned.

                Then I tried a plane iron. In a Stanley #4, a bevel-down smoother, the bedding angle is 45 degrees, as you know. Mine is an older one, but I tuned it and hotrodded it with a Hock cryo iron and cap iron. In this application, the overall contact angle is always going to be 45 degrees, assuming the back of the iron is smooth and flat. The 30 degree bevel merely provides clearance for the cutting edge. Interesting that a plane iron with any bevel angle between about 20 and 37 degrees will cut in a #4 adjusted for a thin shaving, provided the edge retention ability of the particular steel is not exceeded by the resistance of the wood being planed. Obviously, a steeper bevel angle puts more supporting steel behind the edge. As you correctly stated, the sole of the plane guides the cutting edge, not the bevel.

                Finally, I tried a flat-ground knife like Dave's. Well, not exactly like Dave's - his is a lot nicer. I just beat mine out of a piece of chainsaw bar, but it's shaped similar. The results were like using the chisel, only wider. When the looooong bevel rides on the wood, no cutting gets done. When it is inclined above the bevel angle, it bites and cuts.

                So I'm stuck on the "bevel guides the cutting edge" thing. I have this feeling that if I could understand it, I would gain new insight on my tools, and yet I just can't wrap my feeble brain cells around the concept. I'm hoping your shop teacher experience can help me out.

                Parker

                Comment


                • #9
                  Re: Sharpening quiz for single edged tools

                  Originally posted by makinchips View Post
                  Let's start with your bench chisel. If you are talking about a carpenters/cabinetmakers chisel Yes I am then they are designed to cut with the back (flat) face as the cutting guide because they are only used to produce flat, straight cuts. Cutting a gain for a hinge, for example. Agree 100% For carving, it's just the opposite. Carvers rarely are trying to achieve a perfect flat surface. And likely as not, they're cutting into a curved or angled surface. So if the bevel is on the waste side, it's guiding the chip - if not, it's guiding the cut. Right?

                  Let's now move on to the plane. If the iron wasn't protruding below the base it wouldn't cut either and the bevel is on the bottom because the "true" edge of the iron is on the flat (top) side. This would be a serious problem with the chip running up into your eye if a chip breaker weren't installed.
                  Now, like the plane, untill a chip is started, nothing happens. So, using a carving tool with a flat bevel (or any kind of bevel for that matter) you have to tilt the edge initially to begin the chip and then the bevel rides on the surface just created and the chip actually helps hold the tool to the work with some pressure from above (if you think again about the plane, once the cut has started, the chip actually , sorta pulls the plane to the wood). Okay, so you're saying the bevel of a carving tool rides on the cut surface rather than the original surface of the wood. That makes more sense, if the cut surface if flat. If it's concave, or especially convex, then I still don't see how the bevel could ride it.

                  Now, if once you start your chip the bevel isn't riding on the wood, there could only be one answer. You don't have a flat bevel or you may have too large a micro bevel or rounding at the edge. Hence the elevated bevel. I don't think it could possibly be anything else. You know, I've tried microbevels but always came back to a flat bevel. In my work as a trim carpenter, I cut and reshape a lot of shallow mortises for hinges, latches, and strikes, and I find it useful to be able to use a chisel interchangeably bevel-up or bevel-down. Seems like a microbevel interferes with the bevel-down usage, and makes it awkward.

                  I've been fooling around lately with skews and cranknecks, and a couple of bentneck skews are what I really like. Couldn't find them to buy, have to make them. I find they really define the corners of a square mortise well.

                  BTW, single or double bevels on a tool make no difference....only one bevel can work at a time. Might not make a difference in the physics of cutting, but it seems to make a difference in how the tool addresses the work.

                  I hope this helps and thanks for paying attention.....makes me feel like it was worth my time. Certainly was.

                  Like I always say, this craft is all about physics and mechanics. It's not an ART..............what's left IS.

                  Joe,

                  Make Chips!
                  Parker, making cheap shavings out of expensive door jambs

                  Comment


                  • #10
                    Re: Sharpening quiz for single edged tools

                    Originally posted by makinchips View Post
                    I was also a pattern maker.....ya wanna see some pretty chisels and gouges?
                    I'll show you mine if you'll show me yours...

                    I modified this one and used it for a while, then I traded it to my buddy Ernie for a Cman lathe that I've since remotored and got working. It's a inch Eskilstuna from Sweden that I got at a yard sale, covered in rust and the tip all mangled, for 50 cents. The handle is apple.

                    Parker

                    Comment

                    Working...
                    X