Gouge slips below grinding stone

Discussion in 'Tutorials and Tips' started by Richard Preston, Dec 21, 2012.

  1. Richard Preston

    Richard Preston

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    I want to grind a 5/8" gouge at an 80 degree angle. When I position my Wolverine at that angle, the gouge tries to slip below the center line of the stone. If not immediately, then after some steel is removed. The gouge has about 40% of the 'new' length remaining.
    I'm sure someone has already solved this. TYIA
     

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  2. AlanZ

    AlanZ

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    Try using the platform instead of the long arm.
     
  3. Richard Preston

    Richard Preston

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    Precision

    Thanks, Alan, but I want more precision than hand-held.
     
  4. Jeff Gilfor

    Jeff Gilfor

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    Can't you mount the gouge in an adapter, such as the vari-grind jig? Alternatively, take a waste block of wood, and cut a V notch into the top, and clamp or fix it to the platform. That way, you still have the controlled swing back and forth action, but are attacking the wheel higher.
     
  5. Dale Miner

    Dale Miner

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    Don't use the V arm for grinding gouges with a bevel angle that are more blunt than about 60 degrees. Blunt angle geometry with the V arm is very prone to what you are describing, often with dramatic unpleasant results. As Allen stated, using the platform for blunt angles is the safer method. With a little practice, rolling and sweeping the gouge to sharpen become easy, and faster. This applies to rouging gouges also.

    With a blunt angle, the downward pressure from grinding vectors into substantial axial pressure. With any movement or springing of the setup, the gouge gets pushed downward, the bevel is pulled away from the stone effectively causing a catch that forces the gouge into the stone. The grinding wheel is often damaged, and can possibly fracture and disintegrate with force.
     
  6. john lucas

    john lucas

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    Just buy a Hunter carbide turning tool. The #5 has the cutter mounted flat. The cutter has an 82 degree angle which is almost exactly what your after.
    That being said I agree with the platform. It takes practice but once you have it down you'll be able to sharpen the tool in seconds perfectly and safely.
    I have a video that shows sharpening the stewart Batty grind which is 40 degrees but the technique is exactly the same just the angle of the platform is different.
    http://www.youtube.com/watch?v=Xbggxj2kgyc
     
  7. Richard Preston

    Richard Preston

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    The issue is that I want a traditional grind for the curve and the bottom of bowls. I'd rather not have a swept back effect, so that eliminates the vari-grind. Your suggestions made me think of a wood block clamped to the platform in which I could have a cove in which to rotate the gouge. That would eliminate grinding the side.
    I'm following the article by Joe Larese, Oct 2011 pg 24 where he cites Mike Mahoney's recc. to use the traditional grind for hollowing the bottom 3rd of a bowl.
     
  8. AlanZ

    AlanZ

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    Richard,

    You can make a v-block that mounts (perhaps clamps) onto the tool rest platform. Then rotate the rod in that v-block instead of your current configuration.

    If you clamp two pieces of wood, you don't need a v-block, just create a gap that the tool snuggles into.


    EDIT: oops, I must have missed your last message.... we're thinking alike!
     
  9. Richard Preston

    Richard Preston

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    Thanks to all. I have a result with which I am happy. I took a block of wood 2.5 X 2.5 X 6 and cut out a step to catch on the front of the platform. Then I drilled a hole the diam. of the gouge. It clamps nicely. The hole versus a V, is more secure. If I ever decide to do this with a diff. diameter, I can drill another hole. I like the fact that the steel can never flip because it is surrounded by a lot of wood.
    Regards,
    Richard
     
  10. Bill Boehme

    Bill Boehme Administrator Staff Member

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    As you know, with a dry grinding wheel, a very light touch is essential. The problem with the Wolverine at such a steep angle is there is essentially no control over the force between the wheel and tool bevel. The reason has to do with the direction of the resulting force. If that direction is resolved into two orthogonal vectors -- one perpendicular to the tool and the other along the tool, almost all of the force will be along the length of the tool which is in a direction over which you have no control because it is trapped at both ends. That means that you have a dynamically unstable (i.e., self-feeding) condition like a snowball rolling downhill gathering up momentum and accelerating as it progresses. In the case of the bowl gouge, the force between grinder and bevel accelerates much quicker than your reflexes can even recognize it. This means that the platform is far more accurate for controlling the grind. The initial force vectors are still the same, but in this case, the tool is not trapped and will tend to back off if the pressure from the wheel increases and the orthogonal component is solidly restrained. Additionally, the bevel angle can't change so there can't be a runaway condition as in the other case where the tool position is not being restrained.
     
  11. Richard Jones

    Richard Jones

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    Would love to see a pic of your setup, Mr. Preston.
     
  12. odie

    odie

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    I have a blunted bowl gouge that is 65 degree angle, and done on the Wolverine V jig. Probably not too wise to go any steeper than that, but at this angle, it is safe enough.....never had any problems with it.

    I guess it all depends on your particular needs and application, but there isn't many bowls you can't do the bottom interior very cleanly using the 65 degree angle.......

    There is another Mahoney style blunted bowl gouge that I grind using the vari-grind jig.......it can be done.

    ooc
     
  13. robo hippy

    robo hippy

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    Richard,
    That picture makes my sphincters pucker! Scary because I know it will dig in and drop, possible breaking your grinding wheel. The best and safest way to do this grind is on a platform. I am not sure why you want an 80 degree bevel. That is really blunt. 60 to 70 degrees is much more common.

    As for needing more precision than you can get with a platform, well, even with a half round slot in a block, you will not get any more precise. For free hand platform sharpening, the scrapers are easiest, spindle roughing gouges and bottom feeder types are next, and swept back are a bit more difficult. To get a consistent grind on the type of gouge you are using there is really easy, and you would use the same skills that you would use with the wood block there.

    http://www.youtube.com/watch?v=UQ7w6yFhw4c

    robo hippy
     
  14. Steve Worcester

    Steve Worcester Admin Emeritus

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    I don't care why you want the angle, but use a platform, especially if it s a straight across grind. It doesn't have to be as precision as you might think. It is an engage and roll motion. And far safer than using the pocket in the jig.
    I encourage all my students to look for safer ways to sharpen than that jig, I just think it is asking for trouble.

    Just think if you forget to tighten down the clamp!
     
  15. Bill Weaver

    Bill Weaver

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    John,
    I would love a copy of your patterns for the set up. My grinder set up is very similar to yours.

    Thanks Bill
     

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