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Thread: Drill bits, Bright or Surface treated finish?

  1. #1

    Question Drill bits, Bright or Surface treated finish?

    What are Bright finish drill bits used for and what are surface treated finish drill bits used for?

    J&L has a set on sale that I am interested in and it is the same price for the Bright or the Surface treat finishs. I am just learning about machining and tend to do more farm machinery repairs with the drill bits.


  2. #2
    Join Date
    Apr 2001


    I've used both and never noticed a whole lot of difference, although I haven't paid much attention, either.
    I've been using a set of surface-treat 135 degree split point screw machine length drills lately, and like them a lot. I've also got sets of bright 118 degree fractional, number, and letter drills, and they work well too.

    I think the main thing is to get good-quality bits, whichever kind they are. Poor-quality drill bits are useless, and you'll have to end up buying good ones, anyway.

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  3. #3
    Join Date
    Apr 2001
    Portland Oregon


    The black surface treated drills are for steel, polished drills are for aluminum and other non-ferous materials, at least that's what the catalogs say. Funny thing, the outfit I work for deals mostly with aluminum, yet almost all our drills are black. I think they're just more commonly available.

  4. #4
    Join Date
    Jul 2001


    I tend to think the same as Randy, The polished drills are supposed to keep soft gummy materials from sticking to cutting edge. I have both in my drill index and I cannot tell the difference.

  5. #5


    Thanks for the replies.

    I will go with the black surface treated drill bits since I rarely drill soft materials like Aluminum.

  6. #6


    If you want a good set of drills get a set of 135* splitpoints. I have a set of Norseman "high moly alloy" that go through 304 stainless like a hot knife through butter in Mexico! The drills have a bronze color (TiAlN ?). Excellent drills (made in St. Paul, Minnesota). I like their taps & dies (same alloy as their drills) better than my Osborne Warrior & Blue Wizard taps.

    The polished flutes are "supposed" to help draw chips out of deeper holes - less friction. The coatings (TiN, TiCN, TiAlN, and Diamond film) they use these days make a big difference for mass production and resulting tool life. Their hardness and high heat resistance improves edge life even with carbide tooling.

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