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Thread: Drill Sharpening Bench Grinder Addon Design Idea

  1. #1
    Join Date
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    Default Drill Sharpening Bench Grinder Addon Design Idea

    I've been playing with an idea for howcto make a precision drill sharpening jig for my bench grinder, using the grinder rest I made. The rest has the rake angle control and the mitre slot needed, it just needs a way to hold a drill bit and index the drill, feed it in, and set the tip angle.

    The design uses an ER32 collet block to hold the drills and allow for 180 degree flips to do the 2nd flute.

    I also designed a protractor that would make it easy to set the rake angle and the mitre slot distance properly.

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  2. #2
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    The mitre slot is followed by some 3x8x4mm little bearings that one of which is moved to set the tip angle. 118, 135, 90, 82 degrees. I think it will work.

    Setting the drill bit height and angle with respect to the collet block is with a unit that goes over the end of the block and you use a loupe to observe a fine wire that goes across the opening at a specific angle, and you set the drill so its just behind the wire and the drill flute edges align with the wire path.

    A thumbscrew is used to advance the block towards the grinding wheel, one is used to be set as a depth stop once the first flute is ground, and one is used to clamp the block in place so you don't have to worry about it wiggling around in the holder while you're trying to slide it across the grinder rest.

    What do you guys think of my idea? My 3D model gives me confidence it will work, and might perform as well as purpose built DIY units that are pretty commonly seen online.

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  3. #3
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    Waiting to see the final product.

  4. #4
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    Everything below the two thick pieces , look very light and prone to vibration.
    Do you have a diamond dresser.?
    Last edited by 754; 07-06-2018 at 08:06 PM.

  5. #5
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    How do you achieve radial clearance with that setup? Real drill grinders use a cam action to move the drill to achieve radial clearance.

    metalmagpie

  6. #6
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    May 2015
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    Quote Originally Posted by metalmagpie View Post
    How do you achieve radial clearance with that setup? Real drill grinders use a cam action to move the drill to achieve radial clearance.

    metalmagpie
    Not necessarily you havenít seen a SRD. They use a angled block to achieve clearance. Here is video I made of my unit https://youtu.be/astZwPiDRgg


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  7. #7
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    Quote Originally Posted by 754 View Post
    Everything below the two thick pieces , look very light and prone to vibration.
    Do you have a diamond dresser.?
    Those are two pieces of angle iron, with a tube welded in between so I can really crank down the bolt that clamps it in position. I also reinforced the grinder mounting with some angle iron. The 3/4" angle iron on the grinder rest may be a little weak but I'll wait to see after the wheels are properly dressed with a good diamond dresser.

    I have a diamond dresser but need to make a holder for it.

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    Last edited by mattthegamer463; 07-06-2018 at 09:13 PM. Reason: 9

  8. #8
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    With the SRD primary clearance is obtained by having the centerline of the drill below the centerline of the grinding wheel. Radial clearance behind the cutting edge is formed by the conical surface of the inside of the cup wheel.

    To get the secondary clearance with OP's design would require a second grind with a different clearance angle. That would result in a 4 facet drill point which is pretty common on DIY drill grinding setups. The 4 facet grind has been highly recommended by some tool designers. It gives a point that does not "walk" when starting a hole like a conventional point.

    I think the overall concept is excellent. It just needs a more rigid support under the slotted block.
    Last edited by Illinoyance; 07-06-2018 at 09:22 PM.

  9. #9
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    May 2015
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    Quote Originally Posted by Illinoyance View Post
    With the SRD primary clearance is obtained by having the centerline of the drill below the centerline of the grinding wheel. Radial clearance behind the cutting edge is formed by the conical surface of the inside of the cup wheel.

    To get the secondary clearance with OP's design would require a second grind with a different clearance angle. That would result in a 4 facet drill point which is pretty common on DIY drill grinding setups. The 4 facet grind has been highly recommended by some tool designers. It gives a point that does not "walk" when starting a hole like a conventional point.

    I think the overall concept is excellent. It just needs a more rigid support under the slotted block.
    Yes that is true, plus you have a clearance adjustment under the bock. On some drills that need a lot of grinding to recondition you have to twist them a bit in the block. Overall I love my unit because of its simplicity.


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  10. #10
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    You fooled us, clean flat looking pieces in your rendering, then you use hot roll.
    Cold roll or ground material is far better for these tasks. And then you mount to wood.
    Good luck with it.

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