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  1. #1
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    Default Sharpening a Router Plane Blade

    I was sharpening a router plane blade and began to wonder whether it would be an advantage to sharpen it with the edge at an angle across the blade so it would skew slice so to speak instead of cutting the whole width of the blade. Before I go to all the trouble of doing it has anyone got any thoughts or even done it or is the normal operation of a router plane achieving the same thing?
    CHRIS

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  3. #2
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    If you can't skew the straight blade while you are working then you can used the spear point blade for a slicing cut.
    Franklin

  4. #3
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    What Franklin said, Chris - I usually cut with the router slewed unless the space is too confined. Better to keep the blade edges straight, otherwise you can't easily work into both left & right corners of a blind recess. I don't own a spear-point & have never felt I needed one. There must be enough situations where they are useful, or they wouldn't have been invented - I just haven't discovered them yet...

    Cheers,
    IW

  5. #4
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    If you grind a skew on the blade the blade will then cut deeper on the “forward” edge. It’ll be like using a bench plane with the lateral adjuster hard over to one side so the blade digs in on one side only. This is because the bottom of the blade has a 5-10ish degree clearance angle ground on it.
    Nothing succeeds like a budgie without a beak.

  6. #5
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    Chris

    I have no love for the V-blades, which cut on the skew. Once you have used a really sharp straight blade in a router plane, you will not even consider anything else!

    I am not sure if you have used my system for sharpening router plane planes? I post it here every now-and-then ...

    http://www.inthewoodshop.com/Woodwor...aneBlades.html

    Vic Tesolin (Lee Valley) made a video for FWW magazine about it ...



    Regards from Perth

    Derek
    Visit www.inthewoodshop.com for tutorials on constructing handtools, handtool reviews, and my trials and tribulations with furniture builds.

  7. #6
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    While sharpening it I was putting thought into a jig to hold the blade but I was trying to imagine some sort of adapter attached to the Tormek tool rest. In the end I happened across a Paul Sellers video and his method worked. I don't know about the clearance angle aspect Chief Tiff mentions, a rough drawing would be nice showing it.
    CHRIS

  8. #7
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    Quote Originally Posted by Chief Tiff View Post
    If you grind a skew on the blade the blade will then cut deeper on the “forward” edge. It’ll be like using a bench plane with the lateral adjuster hard over to one side so the blade digs in on one side only. This is because the bottom of the blade has a 5-10ish degree clearance angle ground on it.
    That's a very good point, CT, and one I should've remembered to mention too, having mucked about enough with low-angle plane blades. In fact, thinking back, it was probably one of the main reasons I couldn't get on with the first router plane I acquired. It had a much-sharpened blade that had developed a skew, and it was only after I'd gotten rid of it that I came to realise that was the source of much of my frustration (but I ended up making my own "Derek Cohen" imitation, which is much more satisfying & nicer to use, so it turned out better for me in the end. ) I only came to realise how the skewing effect increases exponentially as the bed angle drops, when I made a low-angle, skewed rebate plane. As the blade angle drops below about 20 degrees, the effect of any extra skew on the blade increases rapidly. I have to be extremely careful sharpening the blade because there is little room for lateral adjustment on that plane. The 5 degree or so clearance on the router blades is the equivalent of a very low bed, so you need to be extra-careful to maintain the squareness of the edge if you want your router to cut evenly. No lateral adjusters at all on router planes!

    Cheers,
    IW

  9. #8
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    Quote Originally Posted by Chris Parks View Post
    While sharpening it I was putting thought into a jig to hold the blade but I was trying to imagine some sort of adapter attached to the Tormek tool rest. In the end I happened across a Paul Sellers video and his method worked. I don't know about the clearance angle aspect Chief Tiff mentions, a rough drawing would be nice showing it.
    Chris, it's a hard thing to explain in words, alright. The topic came up a few days ago in another thread & I tried to explain it here (post #35) with models. See if that helps you to visualise the effect. If you are still confused, grab a scrap of wood, make a 10 degree 'ramp' and put an old blade or a bit of tin plate on it & I twist it a little from side to side. I think you'll soon get the picture...

    Cheers,
    IW

  10. #9
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    Ian, firstly thanks for your input but confusion still reigns so to speak. I can't see in your link any reference to clearance angles, is this just a terminology thing between the two threads? I guess it would be safe to say that I am missing the point by about 1000km.
    CHRIS

  11. #10
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    I found this

    Honing guides are useful things. If you have one, now is a good time to use it. Most block and bench plane blades are ground to 25° but some smart folks argue that there need only be clearance under the heel of the bevel. In other words, since the average bench plane blade is bedded at 45°, any bevel angle 10° or so less than that will provide the needed clearance. And a thicker bevel is stronger so the edge should last longer. Bench plane and block plane blades have traditionally been beveled to 25°. Our blades for the handmade wooden planes were specified by James Krenov to have a 30° bevel. Chisels get different bevel angles for different tasks: 25° or lower for paring, 30° or more for chopping. Experiment a bit with different angles to see which one works best for the wood and your style of work. A honing guide helps with all this by establishing an angle and sticking to it. It can also shorten the whole process by letting you raise the blade a degree or two so that you’re only honing the very edge. The angle of the bevel is determined by how far the blade sticks out of the honing guide.

    From here
    http://www.hocktools.com/tech-info/sharpen.html

    It is as clear as mud to me but I will re-read it a few times and see if I can make sense of it.
    CHRIS

  12. #11
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    OK, after a discussion with another forum member I was able to get it so to speak. This might seem elementary stuff to most people but I have a 3D mental block as in I can't think in it and can't draw it so stuff like this leaves me just as confused as a person with Dyslexia trying to read a book. I once sat sat for a tech drawing exam and wrote my name on the top of the paper and it then finally dawned on the teacher that I was a lost cause. Such is life!
    CHRIS

  13. #12
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    Quote Originally Posted by Chris Parks View Post
    OK, after a discussion with another forum member I was able to get it so to speak. This might seem elementary stuff to most people but I have a 3D mental block as in I can't think in it and can't draw it so stuff like this leaves me just as confused as a person with Dyslexia trying to read a book. ....
    Which is why I suggested making a mock-up from a scrap of wood.

    Make a wedge that is about 10 degrees (near enough to the clearance angle of a router blade), & sit it on the table. Cut a "blade" from a piece of foil or cardboard and sit that on the wedge. Sit the blade square on your wedge, & if the edge of your 'blade' is square, it will make contact with the table top right across. Now cut the 'edge' of your 'blade' deliberately off-square by a few degrees & place it back on your wedge. You will see that the 'pointy' side of your blade edge now makes contact with the table but the other side sits well back from it.

    You can bring the edge into contact with the table top by slewing the blade over (this is what you are doing when making lateral adjustments on an ordinary plane), but a router blade is fixed, so you cannot compensate for an off-square edge, and the pointy side will cut deeper than the 'trailing' side.

    This effect of an off-square edge increases as the bed angle drops. A router blade has a very low effective 'bed' angle (which is the same as its clearance angle ), so the effect of sharpening the blade off-square is much greater than if you sharpen the blade for a standard pitch (45* bed) plane off-square by the same amount. You are probably aware that you have to be more fussy grinding & sharpening low-angle block-plane blades, you tend to run out of lateral adjustment room pretty easily if you let them get much off-square. My 60 1/2 (they have a 12* bed) taught me this many years ago!

    Cheers,
    IW

  14. #13
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    Do whatever works. I doubt that many people sharpen a router plane blade identically and how you do it might differ based on what you have in the shop.

    Agree with derek about the vee blade vs. straight. I just can't really figure out what good a vee blade is.

    I generally use as fast of a stone as I can find for all but the very tip work on a router plane blade, there's nothing particularly stimulating about sharpening them and when I've gotten used router plane blades, the efforts made to sharpen them before they were put away usually confirms that the prior owner didn't find sharpening them stimulating at all (or maybe they were doing mostly cross grain work where it didn't matter that much).

  15. #14
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    Chris, the geometry of the cutter and how it sits on the plane requires the edge of the blade to be parallel to the long axis of the plane to be coplanar with the plane sole. If you put a skew to the cutter, then it won't be coplanar. It will cut a groove.

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