need to make a 3/4" hole larger on 1" steel flatbar

Discussion in 'Tools and Fabrication' started by meatloaf, Dec 14, 2010.

  1. meatloaf

    meatloaf

    Messages:
    1,611
    Location:
    So. Austin, tx
    Like the title says, I built my 60 a rear bumper... bought the 3/4" shackles and drilled the 3/4" hole on the 1" flatbar and the hole was too small. Went back to Lowe's, spent ~$25 for a 1" bit tried to make the hole bigger and the bit broke quickly. :mad: Is there a way, hopefully cheaper, to make the diameter bigger?

    Thanks in advance,
    ML
  2. batcon

    batcon

    Messages:
    448
    Location:
    Carmel Valley, CA
    Be careful, with that big a bit, it can hurt you. I bet you can bring it to a welding shop or a machinist and they would do it for a reasonable price.
  3. splitshot

    splitshot SILVER Star

    Messages:
    5,499
    Location:
    Podunk, Arizona
    Know anyone with a plasma cutter?

    How thick is the material?
  4. fj40charles

    fj40charles GOLD Star

    Messages:
    2,779
    Location:
    Texas
    Magnetic drill with annular cutter.
  5. meatloaf

    meatloaf

    Messages:
    1,611
    Location:
    So. Austin, tx
    Thanks for the warning... I would have to pull the bumper off.

    I have a fried with a plasma cutter but it won't cut thick metals. the material is 1" thick.

    Pardon my ignorance, but what is an annular cutter?

    Thanks All.

    Luis
  6. 2mbb

    2mbb SILVER Star

    Messages:
    4,490
    Location:
    WC, CA
    I did a similar thing. I'm not sure how I got it I think I went really slow with the larger bit and used a lot of cutting compound. Although with mine I had not yet welded the bumper together, so I just had to deal with a piece of 1" flat stock. I don't think I went all the way up to 1" in one shot (or at all).

    You might also try a die grinder, although my experience using those to ream holes by hand is that you get a lot of chatter and the end result is not necessarily a round hole.

    I think an annular cutter is something like a hole saw--it cuts around the outside diameter of the circle, but not through the middle.

    did you think about using a smaller shackle? Good luck. I know this situation sucks.

    edit. I've never used one but something like one of these reamers might work, specifically the "construction reamer". They are not cheap, though. Maybe you can find a machine shop with one and they can do it on your truck. http://www.mcmaster.com/#center-reamers/=a5pj2k
    Last edited: Dec 15, 2010
  7. meatloaf

    meatloaf

    Messages:
    1,611
    Location:
    So. Austin, tx

    thanks mbb. I googled the anular cutter and now I have an idea of what it looks like. I may just go with slightly smaller shackles or the die grinder.

    My next project is the front bumper, just like yours. I printed out the specs from your post ~3 months ago but wanted to finish the rear bumper before starting on the front. So, I may be emailing you for help.
    Thanks again.
    Luis
  8. nat

    nat

    Messages:
    1,994
    Location:
    Los Gatos, California
    When drilling large diameter holes, you want to run the drill chuck at a very low RPM. On my drill press I run it at 350 RPM for big holes. If you run your bit fast, you can heat the material and work harden it, then you are really screwed.
  9. fj40charles

    fj40charles GOLD Star

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  10. spressomon

    spressomon glutton

    Messages:
    11,076
    Location:
    Central Coast
    Die grinder is really your only option if you want to enlarge the hole(s) with the bracket already attached to the bumper.
  11. Pin_Head

    Pin_Head

    Messages:
    11,490
    Location:
    OC, CA
    You can drill it larger; just don't go from 3/4 to 1 inch in one bite. Go 13/16, then 7/8, etc. Drill with a slow chuck RPM and use cutting oil.

    HF has a Silver and Demming type drill set from 9/16 to 1 inch in 1/16 increments for about $30. It is one of the few things they have that is worth it. I have drilled hundreds of holes with them.

  12. haryv

    haryv

    Messages:
    1,305
    Location:
    North of the 49th parellel
    Nat, I was drilling some 3 inch wide 5/16 bar stock and found it was better to use water with my titanium drill bits vs some kind of cutting oil. Is there a reason for that? I can actually "feel" the bit cutting into the metal and nice kerlyque spirals of steel coming up vs bits when using oil. BTW, I did not use cutting oil but just some off the shelf penetrating oil.

    Also, can some one vouch for drill doctor?
  13. zebrabeefj40

    zebrabeefj40

    Messages:
    3,112
    Location:
    southeastern IN
    Drill Doctor makes a pretty nice drill point once you learn how to use it. I have one and use it all the time. Will sharpen a drill bit to a nice split point too. It is a great drill sharpener for the price.

    Nick
  14. nat

    nat

    Messages:
    1,994
    Location:
    Los Gatos, California
    Water based cutting fluids are fairly common. Bits like to stay cool. I use rubbing alcohol sometimes when machining aluminum.
  15. meatloaf

    meatloaf

    Messages:
    1,611
    Location:
    So. Austin, tx
    Pin Head,

    went to HF and bought the drilll bits you suggested... will try again this weekend.

    All,
    I have not been able to find the cutting oil and have been using motor oil... any objections to this?
  16. Pin_Head

    Pin_Head

    Messages:
    11,490
    Location:
    OC, CA
    Much better than Mazola, spit or KY jelly.

    You are going to need a half inch drill with a cheater bar on the handle to hold that thing steady enough that it won't get away from you.
  17. Blue77FJ40

    Blue77FJ40 SILVER Star

    Messages:
    2,146
    Location:
    MD
    You're only trying to enlarge the hole enough to fit the pin from the shackle, right?

    I would take my black&decker rotorary tool (like a dremel, but more robust and longer lasting) with a sanding drum and slowly and evenly enlarge the hole.

    My 2 cents.
  18. zebrabeefj40

    zebrabeefj40

    Messages:
    3,112
    Location:
    southeastern IN
    You can get cutting oil from a plumbing supply house. Ask for heavy threading oil (same stuff they use while cutting threads on pipe). Smells nasty but works great for what you're doing.

    Nick
  19. meatloaf

    meatloaf

    Messages:
    1,611
    Location:
    So. Austin, tx
    Hello All,

    I went to HB and bought the bits that Pinhead suggested. That did the trick! Thanks to all of you for the suggestions.

    Luis (aka meatloaf)
  20. misterpepper

    misterpepper

    Messages:
    279
    Good to see that it worked out. My suggestion would have beeen to try a step drill as it should basically center itself as it reams each progressive hole size bigger. I would imagine the material is thicker than the steps on the drill bit so you would either have to access the hole frim the far side as well, or finish it off with either a regular bit of the correct size or a die grinder using the correctly sized step as a guide.

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