What's the purpose of a three flute drill bit ground to 78 deg.?
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  1. #1
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    Default What's the purpose of a three flute drill bit ground to 78 deg.?

    Now before anyone submits to the urge to reply "to drill holes", i get that part. But why three flutes and 78 deg. rather than the more common 60 deg.? Are they for a specific material? They are HSS.

    I picked these up in a pile of other stuff i bought.

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    Probably a "core" bit for cleaning up cored holes in a casting. Not to be confused with core bits that cut out a cylindrical slug of what ever material they are drilling.

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    One more cutting edge-higher feed rate.

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    +1 to Sam.

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    Thee flutes (or four) are used on core drills because they will self-center in an existing pilot hole, where a standard two flute drill will tend to chatter and grab.

    Larry

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