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  1. #1
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    06-21-2010
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    what is the difference in bevel angle and edge angle!

    Hi, Guys:

    I thought this was going to be a no brainer but I'm a little confused and overwhelmed. Today I was going to revisit the sharpening of my chisels so I could practice the lathe. Here's were I'm at.

    Identifying the chisels:

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    With the books, I've determined I have 2 rough gouges, 2 skew chisels, 1 parting tool, 1 spindle gouge and two scrapers (one is rounded, the other like a triangle).

    I thought a methodical approach would be to start sharpening a roughing gouge since it's the first tool to use.

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    All of the chisels have a film on them and need shaping and/or sharpening.

    Okydokey! NOW is the problem:

    The Tormek speaks about bevel angles and edge angles defined in their terms for use with their jigs. I can live with that, but what the dandelions do they mean? I'm suffering information overload and thought you may help simplify the matter. I don't know how to use a protractor, and don't really know if I have the right kind of protractor. I'm really bad at math and angles. Timmer explained the Acute angle is the smaller measurement. I've always thought that if you were in acute pain that made it big, and obtuse, meaning: "thick in the head, like me", made it smaller. I have to really think in reverse to understand the terminology. Having said this, can you decipher these instructions:

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ID:	5677 I understand the language but not the graphics. How are we looking at the blade. From the top? I've been playing with blades, protractor (?) and profiles all afternoon and I'm frustrated that I can't see it!.

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ID:	5678 This is the next page in the manual describing the difference between a bevel angle and an edge angle, as applied to their system. I've tried reproducing the graphics by holding my chisels every which way, and measuring my protractor that is useless for this application, and for the life of me, the math doesn't pan out.

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ID:	5679 This is their measuring jig and easy to follow except I'm not sure how to hold a skew to measure the protrusion... This jig leads to this chart, which is where the basis of my confusion lyes:

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ID:	5680 This chart tells you the different angles they recommend for these chisels and how to set the jig up.

    Here's my confusion:
    1. When they explain the difference in bevel/edge angle, on the second image they have a) as the edge angle, and B) as the bevel angle.
    2. In the selection chart for the shews: they have a=45*. And a 20* something, measuring something. They all look the same.
    3. The difference I see is that when they list a=30, the 20* line, and the distance from the edge to "depth of bevel(?)" is deeper than when they have the a=45*.
    So, how are chisels measured?????

    Hope some of this makes sense, cause I'm all confused. Thanks!!!!!!!!!!
    Elizabeth
    I think, therefore I'm more confused than when I began.
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  2. #2
    Join Date
    06-15-2010
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    Re: what is the difference in bevel angle and edge angle!

    Aha - I b'lieve I understand your quandary. As Tormek uses the terms, the EDGE angle is the acute angle between the two sides of the edge... like the top (inside the flute) to the bevel's surface. The BEVEL angle, by comparison, is the obtuse angle between the bevel and the SHANK... it's the angle that defines how much of an "elbow" there is between the shank (which leads up to the handle, and represents the upper arm) and the bevel (which leads down to the edge, and represents the forearm).

    Mostly... I wouldn't worry very much about the exact angles. Eyeball it - set up the sharpening jig so the bevel rests flat (or as near flat as it'll go) against the wheel. Maybe make a note of that setting for later reference. As you work at the lathe, you'll decide if you want a sharper (more acute) or blunter (more obtuse) angle than you got by eyeballing it. Even then, the numbers aren't very important - if you need it a little more acute, eyeball it a little more acute.

    In that first page "Shape and Sharpening", you're looking at the "edge of the edge", as if somebody cut the tool in half lengthwise, or as if you were holding a bench chisel up to the light and sighting along its edge.

    The same goes for the second page "Edge Angle and Bevel Angle"; you're sighting along the edge.

    In that skew selection chart... they're showing the EDGE angle (as they call it out). If the angle between the two bevels (wrapping around the edge) is 45 degrees, that's a pretty blunt angle and so the bevels will be short. If it's only 20 degrees, it'll be more like a razor blade... and the bevels will be longer. Like... if you cut/sand the end of a dowel to an edge, with the angle wrapping around the edge at 90 degrees, each bevel will be pretty short. If you cut/sand it some more until you have a very thin angle like 15 degrees wrapping around the edge, it'll be shaped more like a pencil, with very long bevels.
    -- Tim --

    What???
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  3. #3
    Join Date
    06-22-2010
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    Re: what is the difference in bevel angle and edge angle!

    'Liz, Tim got it right when he advised to just make your chisels look like they were new. Except for what's written about safe operation of the machine, don't worry about the typed technical details. Look at your gouge and compare to their picture of a gouge. The cutting edge is obvious, that's what you want to perfect. Same goes for a skew or parting tool. Althought the factory grinding isn't perfect - honed & ready to cut - it is the pattern you want to be guided by. As you work with the tools you've honed you will make adjustment to suit your own style of turning.

    Maybe this will help:
    http://www.mathsisfun.com/angles.html

    It's not that hard, you want a sharp cutting edge. I've known guys who couldn't read or write but they could sharpen any tool to a razor's edge.

    You will get this! You conquered complex angles on tiny boxes. In about 6 months you'll be able to sharpen any of those tools to a razors edge with one eye closed.

    art
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  4. #4
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    06-15-2010
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    Re: what is the difference in bevel angle and edge angle!

    ...AND both hands tied behind her back.

    By the way, MathIsFun is kinda' cool. It wouldn't've been much help this last week as I was working out the details on my ellipse-plotting algorithm, though...

    MAN accurate ellipses are complicated! They LOOK dead simple, but there's a LOT of equations floating around in there!
    Last edited by TDHofstetter; 03-18-2011 at 4:12 am.
    -- Tim --

    What???
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  5. #5
    Join Date
    06-19-2010
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    Re: what is the difference in bevel angle and edge angle!

    Elizabeth,

    Set up the jig so that the bevel on your chisels is laying flat against the grinding wheel (just eyeball it). Take a black marker and mark the bottom side of the bevel. Place it against the wheel and rotate the wheel a bit by hand. Now look at the mark you made. If the mark is removed for the full length of the bevel, the set-up is perfect. If it's more towards the tip, move the tool towards the wheel. If it's towards the heel, move it away from the wheel. (these are very small adjustments)
    Cody

    "The reverence that the object maker has for the materials, for the shape, and for the miracle of his skill transcends to God, the Master Craftsman, the Creator of all things, who uses us, our hands, as His tools to make these beautiful things." Sam Maloof (1916-2009).
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  6. #6
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    06-21-2010
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    Re: what is the difference in bevel angle and edge angle!

    Thank you!!!!!!!!!!!!!!!!!!! Took your advice and here's the results of my efforts. Still a ways to go as you will see:
    • Genius at work:
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    • As I read in the books, I polished the backs of the chisels and rounded the sharp corners so they would slide easier on the tool rest and be a pleasure to hold:
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ID:	5719 I didn't hone the backs because I decided to plunge in and get these shaped and sharpened. I'll hone all at the end. I selected the flat chisels first thinking they may be easier to start with than the gouges. I did both skews, both scrapers, and the parting tool.
    • I started shaping the larger skew and set the jig for the 45* edge thinking that if I mess it up it won't be that great a loss as it's probably larger than I'll use. I also chose the heftier angle for this in case I do use it for roughing.
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ID:	5720 This side came out better than the other, but needs more work. I'm having the Dickens shaping the very tip without creating facets.
    • This side is terrible, but I'll keep at it.
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ID:	5721 You see what I mean by the tip and facets? I'm tempted to give an arc to the edge. It'd be easier to sharpen but it probably is not prudent for me yet.

    The smaller chisel I'll make into a finishing one with the longer bevel.

    So what you think for my first try?
    Elizabeth
    I think, therefore I'm more confused than when I began.
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  7. #7
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    06-20-2010
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    Re: what is the difference in bevel angle and edge angle!

    Elizabeth it can get confusing sometimes. Most angles that are talked about are in reference to 90 so if someone is talking about a 40 then the opposite of that is 50. Here is a page from Doug Thomas website and it is self explanatory and is a help to me. I have it on a clipboard by the grinder. He shows the actual cut in reference to a particular tool.
    http://www.thompsonlathetools.com/sharpening.asp I think it will be a help to you. I just place my tool next to it and compare. You will get it the hang of sharpening, I have no doubt.
    Fred
    http://steercreekwood.com/

    A clear conscience is usually the sign of a bad memory.
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  8. #8
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    Re: what is the difference in bevel angle and edge angle!

    I just printed it. Thank you! I'll get there.... Can't wait to use the tools on the lathe!!!!!!!!!
    Elizabeth
    I think, therefore I'm more confused than when I began.
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