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  1. #16
    Join Date
    Nov 2019
    Location
    Brisbane
    Age
    67
    Posts
    354

    Default Difficult drilling

    Hello Grahame.
    For difficult steel definitely reduce the rpm, use a stub drill to increase rigidity and if necessary reduce the rake angle so the drill is not so aggressive. Good brand drills are a must.
    Regards
    BC

  2. #17
    Join Date
    Jan 2004
    Location
    Mackay North Qld
    Posts
    6,272

    Default

    Quote Originally Posted by steamloco1954 View Post
    Hello Grahame.
    For difficult steel definitely reduce the rpm, use a stub drill to increase rigidity and if necessary reduce the rake angle so the drill is not so aggressive. Good brand drills are a must.
    Regards
    BC
    Hi BC
    I went back today and did all that bar using the stub drill.
    I had previously written I had set the slowest speed. That was not correct due to my poor eyesight incorrectly reading the chart on the DP. I am waiting on new prescription glasses.

    I had to take my linisher outside to see well enough for grinding the drill to a shallower included angle.

    It was tough to get through but not as bad as it has been. The difference being, it got hard immediately just before breaking through.

    I am assembling a set of stub drills by means of breaking the longer ones.

    Only two more holes to drill, now. Thank goodness!

    Thanks
    Grahame

  3. #18
    Join Date
    Nov 2019
    Location
    Brisbane
    Age
    67
    Posts
    354

    Default drill grinding.

    Quote Originally Posted by Grahame Collins View Post
    Hi BC
    I went back today and did all that bar using the stub drill.
    I had previously written I had set the slowest speed. That was not correct due to my poor eyesight incorrectly reading the chart on the DP. I am waiting on new prescription glasses.

    I had to take my linisher outside to see well enough for grinding the drill to a shallower included angle.

    It was tough to get through but not as bad as it has been. The difference being, it got hard immediately just before breaking through.

    I am assembling a set of stub drills by means of breaking the longer ones.

    Only two more holes to drill, now. Thank goodness!

    Thanks
    Grahame
    Hello again.
    Changing the edge included angle may help but I was referring to grinding the flute to decrease the edge rake angle. The rake is the spiral angle of the flute. By reducing that the edge is stronger and less prone to burst thru surge. I did a video on using bench grinders and showed how to change drill rake angle. Also good for brass and some plastics. Making stub drills is OK but those made recently don't have a web thinning process. They are fat to the tip and point split to compensate.
    The best with your project. BC

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