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Thread: Sharpening question

  1. #1
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    Sharpening question

    Just learning to sharpen. New chisel. How much of the back of a chisel should I flatten and polish?
    Bob C

  2. #2
    For chisels you should flatten the entire back. Plane blades you don't need to do the entire back.

  3. #3
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    Bob, with all blades - chisel or plane - the backs need to be coplaner. This does not mean flat or mean polished. Flat to me means that the surface is even, but not polished. Polished means just that.

    Why coplanar? Well, chisels often are run along a guide, such as when paring a perfect 45 degree angle ...





    ... and any curve in either will lead to inaccuracies.

    Plane blade backs need to be coplanar to bed flat and securely, whether wooden or metal bodies, since any movement will create chattering.

    In all cases, the amount of polish only needs to be immediately behind the bevel. The amount is infinite and theoretical to state. In practical terms, I aim for 1/2” - 1”. The level of polish should be exactly the same as the bevel, itself. There is much variation how you achieve this and the number of microns one aims for. I aim for a 13K waterstone on both sides.

    Regards from a cold Prague

    Derek

  4. #4
    Quote Originally Posted by Bob Cooper View Post
    Just learning to sharpen. New chisel. How much of the back of a chisel should I flatten and polish?
    Is it a new, currently made, or an older chisel that is new to you? If it is a chisel made by Veritas or for that matter any of the better makers the back will need very little work with polish on only last 1/2" or so like Derek posted. Folks in these parts make too much of a big deal out of polishing. The most important steps are the grinding and honing, polishing is adding the cherry on top. One other thought, shiny doesn't mean sharp.

    ken

  5. #5
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    I’ll show you two example. One is an old marples chisel and one a new Stanley sweetheart Christmas present

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    Quote Originally Posted by Bob Cooper View Post
    Just learning to sharpen. New chisel. How much of the back of a chisel should I flatten and polish?
    As much of the back as will affect the work for which the chisel is used.

    Some of my chisel's backs are atrocious but they are still effective at their tasks.

    If a chisel is only used for paring dovetails in 1/2" thick pieces, it will not do better work if all 6" of the blade is polished to a mirror finish.

    A chisel used to smooth the floor of dados will benefit by having a back that is coplanar over its length as Derek mentions.

    jtk
    "A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty."
    - Sir Winston Churchill (1874-1965)

  7. #7
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    ok...here's pictures of the two chisels. The smaller one is the marples. Two pictures of each. my assumption is i need to go back and more fully flatten the stanley (at least) but do you go all the way to the tang (wording?) or is 2-3" far enough. Do i need to also back up and more fully flatten the marples?
    Attached Images Attached Images
    Bob C

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    Quote Originally Posted by Derek Cohen View Post
    Bob, with all blades - chisel or plane - the backs need to be coplaner. This does not mean flat or mean polished. Flat to me means that the surface is even, but not polished. Polished means just that.

    Derek
    So Derek...what's confusing to me some is how does one determine if the surface is coplaner? So for example i have a new set of Stanley Sweatheart chisels and a new LN plane (very nice Christmas presents from my wife). I understand that the backs need to be flat/coplaner and the edge sharp. I also have some older Marples that i figured i could experiment with.

    So for the newer tools ...and i'm just thinking about the backs right now...do i need to run them thru the various grits to eliminate the mill marks?

    I have 4 DMT diamond plates (coarse thru very fine) to work with. with these in mind (or speak in terms of waterstone grits) how fine do i need to smooth the entire back before working on the front 1/2" or so?
    Bob C

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    Bob, At this point it appears the Stanley has a hollow in the center. Many folks using Japanese chisels will say that isn't a problem.

    The Marples doesn't look too bad.

    At this point my usual procedure is to give the back a few extra strokes each time a chisel is sharpened. Over time it gets better.

    This is where the end of the stone comes in handy. A FWW article from years ago mentioned working the back of blades across a stone. It doesn't matter if the edge travels beyond the side of the stone.

    Of course, YMMV!!!.png

    jtk
    "A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty."
    - Sir Winston Churchill (1874-1965)

  10. #10
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    Quote Originally Posted by Bob Cooper View Post
    So Derek...what's confusing to me some is how does one determine if the surface is coplaner? So for example i have a new set of Stanley Sweatheart chisels and a new LN plane (very nice Christmas presents from my wife). I understand that the backs need to be flat/coplaner and the edge sharp. I also have some older Marples that i figured i could experiment with.

    So for the newer tools ...and i'm just thinking about the backs right now...do i need to run them thru the various grits to eliminate the mill marks?

    I have 4 DMT diamond plates (coarse thru very fine) to work with. with these in mind (or speak in terms of waterstone grits) how fine do i need to smooth the entire back before working on the front 1/2" or so?
    Bob, scribble/cover the back of the blade with a black magic marker or paint on marking fluid. Then rub them on wet-and-dry paper glued to glass, or a fine diamond plate. That will help you determine where there are low spots. As long as the low spots are in the middle and not at the edges/front/back, then you are good to go. If you need to work the back down, I prefer wet-and-dry.

    Regards from Prague

    Derek

  11. #11
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    ok...thanks guys. i'm sure i'll have other questions as i go along. Having probably never really used a sharp tool before i'll be developing a feel for this over time
    Bob C

  12. #12
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    Quote Originally Posted by Bob Cooper View Post
    Just learning to sharpen. New chisel. How much of the back of a chisel should I flatten and polish?

    What happens is that you register a comfortable amount of the back of the chisel on your honing media and that's the amount that gets flattened and polished. If your hand is cramping and your knuckles turning white trying to register a tiny sliver then you're obviously doing it wrong. The amount depends on the width of the chisel. Just do what feels comfortable. It is essentially a one-time only process. Afterward, you're just chasing and polishing the wire edge away produced from honing the bevel. As you use the chisel up, the polished back will follow up the chisel from the aforementioned burr chasing.

    Again, slap whatever amount of the chisel on the stone that makes it a comfortable process. Don't overthink it. The back is flat enough when a few strokes will move the burr back to the beveled side of the chisel without lifting the chisel on the stone and producing a back bevel. Polish is inevitable.
    Last edited by Charles Guest; 12-29-2019 at 6:22 PM.

  13. #13
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    Most of the things I use a chisel on are no more than one inch thick.
    That much should be flat enough.

    I'm with Charles on this.

    You're making furniture with these - not performing surgery.
    If you can pare end grain of something like soft pine, it's fine.

    http://www.antiquetools.com/sharp/

    https://toolsforworkingwood.com/store/blog/841

  14. #14
    While the photos are soft and blurry it appears the small chisel is a pre-1933 Marples. If so you may have a very good western chisel.

    ken

  15. #15
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    All...thanks go much. Ken these Marples have the blue plastic handles and i think they are about 5 years old is all so they are not that old.
    Bob C

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