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  1. #1
    Join Date
    Nov 2019
    Location
    Brisbane
    Age
    69
    Posts
    452

    Default Setting up to grind large countersink

    SAM_0708.jpgHello from the Old Goat.
    I thought this might be interesting as I time the countersink to the grinder's cam. Just like timing a car engine the procedure has only a few steps but the instructions are hard to find.
    On the top of the fixture there is a sliding plate that is slid into a slot in the cam driver. The cam is timed to the shaft. An engineers square is placed on the parallel on the table and brought up behind the countersink. The rear flute has both leading edge and trailing edge aligned with the square. Both edges are perpendicular to the table. The chuck or collet is now tightened. When the fixture is run and reaches this point the roller is going over the cam and the shaft is retracted, moving away from the wheel. Further rotation advances the shaft and the wheel grinds the land behind the edge. I have a set of cams from 1 to 8 lobes.
    Around 15 mins to regrind a $200 cutter.
    Regards
    BC

  2. #2
    Join Date
    May 2011
    Location
    Murray Bridge S Aust.
    Age
    71
    Posts
    5,942

    Default

    Bit hard to tell from the pic, but is the cutting edge ground back a thou or so, or is it the periphery of the cutter ground???
    Kryn
    To grow old is mandatory, growing up is optional.

  3. #3
    Join Date
    Nov 2019
    Location
    Brisbane
    Age
    69
    Posts
    452

    Default Regrinding countersinks.

    Hello Kryn.
    The same as grinding a twist drill the material is removed behind the cutting edge. The cam controls axial movement as the cutter is rotated. Once the cutting edge is at right angles to the wheel the grinding starts. I have ground the rake face on some countersinks when the owner has made adjustments to restore the sharpness. You need a cup wheel small enough to match the radius ground into the face of the cutter. A good finish is required on this job but accuracy is not as the cutting edge height is levelled when the tool is ground in the fixture. Be careful as the countersinks get extra hot as they are ground and will burn you for a few minutes.
    Regards
    BC

  4. #4
    Join Date
    Sep 2008
    Location
    Riddells Creek, Vic.
    Posts
    831

    Default

    That’s a good setup BC, I would like one of those attachments myself, makes sharpening fast and easy. Not all counter sinks have evenly spaced teeth though, Austra for example used to offset one tooth by a couple of degrees on their 4 flute c/s to try and reduce chatter although I am not sure that it made much difference, sharpening them was a bit of a pain.

  5. #5
    Join Date
    Nov 2019
    Location
    Brisbane
    Age
    69
    Posts
    452

    Default Grinding large countersinks.

    Hello Techo1.
    Now you have me scratching my head. I think a single flute cam and index the cutter in the collet to a finger for each flute. That is a lot of work. Another way to grind this type of cutter is to index to the flute and grind 2 clearance angles like a 4 facet drill.
    Regards
    BC

  6. #6
    Join Date
    Nov 2019
    Location
    Brisbane
    Age
    69
    Posts
    452

    Default Countersink grinding video.

    Hello again.
    I have just watched a good video explaining relief grinding a countersink. My Yankee machine is easier to use I think but Stephan makes great videos.
    https://www.youtube.com/watch?v=CbsaEQljK-Y
    Regards.
    BC

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