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Thread: Drilling Into Cast Iron

  1. #1
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    Drilling Into Cast Iron

    What is the best type of drill bit to use when drilling 1/2" holes into cast iron? What may work the best?

    Thanks!

    - Keith
    "Listen, here's the thing. If you can't spot the sucker in the first half hour at the table, then you ARE the sucker. "

  2. #2
    I used a cobalt (the mineral, not the blue borg brand) bit when drilling into my cast iron table without any hitch. I believe HSS will also work, provided it is sharp. Cast Iron is not as hard as you might think, compared to steel.

  3. #3
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    I did use a regular HSS drill without problem.
    Ed.

  4. #4
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    No lubrication is necessary as the carbon in the steel will lubricate it enough. Cast iron drills and taps easily.

    CPeter
    Last edited by CPeter James; 12-11-2008 at 11:29 AM.

  5. #5
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    HHS drill bits are fine to do the job just make sure you bore a pilot hole first, I have found that if you drill several holes steping up a couple of sizes each time works best for me

  6. #6
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    I think I used HSS bits....really any decent bit should work ok. just take your time and it drills quite easily (no surprises).
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  7. #7
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    I just purchased a set of reasonably price DeWalt pilot point bits that don't require the pilot hole. They work great in cast iron with speed at minimum but are a bit agressive in wood.

    Sarge..

  8. #8
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    A standard borg HS twist drill without lubrication will work fine. Cast iron IS NOT a hard material. There's no need for colbalt, M-42, or carbide, unless that is what you have sitting around.
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  9. #9
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    Good deal!! Thanks for the info, guys!!

    - Keith
    "Listen, here's the thing. If you can't spot the sucker in the first half hour at the table, then you ARE the sucker. "

  10. #10
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    Keith

    a regular drill bit would work fine. I would use a smaller bit first and work up to the larger size.

  11. #11
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    Depending upon the bit, I'd suggest using a punch to put a nice little mark/dimple where you can put your bit so it doesn't wander on you.

    Don't forget about placing a towel or something to catch shavings if they'll fall on anything you can't easily clean up.

    As everyone else said, CI drills very nicely and cleanly...with a sharp bit, of course.
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  12. #12
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    What Chris said about the punch. Then a reasonably sized pilot hole. Then the the real McCoy. Drill at a steady pace so you can control the drill, itself.
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  13. #13
    Keith, I have only one experience at this, so take it for what its worth. But, I decided I should have used a guide clamped in place - perhaps a 2" thick piece of oak thru which the correct size hole had been drilled on a drill press.

    If you do a pilot hole, then double this procedure. I had difficulty with creep, but it may have been lack of the correct size pilot hole. Just a thought.

  14. #14
    I center punched, drilled a pilot hole that was big enough to accept the splitpoint width and drilled it out to size. No lubrication required. Drilled easily with a cheap-o Ryobi bit out of a kit I got as a gift somewhere down the line.
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  15. #15
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    Quote Originally Posted by Chris Padilla View Post
    Depending upon the bit, I'd suggest using a punch to put a nice little mark/dimple where you can put your bit so it doesn't wander on you.
    Good point. I almost always use a center drill whether I’m hand drilling or using my mill. (comes from my machinist training).
    You don’t need to drill a pilot hole when you start with a center drill….
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