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Thread: Problem drilling mild steel flat bar

  1. #1
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    Problem drilling mild steel flat bar

    Hello all, I was making a few 4"x4" wall brackets from 10ga wild steel and needed to drill 8 mounting holes for #10 screws. 7 of the 8 hole were no problem but while drilling the 5th hole the titanium coated bit just spun in place making a small dent. I used plenty of drilling oil. I tried two times and on the third attempt the drill bit glowed bright red. I switched bits, more oil, and still no luck. Finally I flipped the piece over and successfully drilled it from the other side.

    Did I do something wrong? Cheap mild steel had a hard spot? I probably hardened the spot with the heat.

    Is this common?
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    Re: Problem drilling mild steel flat bar

    The flat bar may not be A36.
    Are you using scrap ?

    Dave

    Quote Originally Posted by Flyer58 View Post
    Hello all, I was making a few 4"x4" wall brackets from 10ga wild steel and needed to drill 8 mounting holes for #10 screws. 7 of the 8 hole were no problem but while drilling the 5th hole the titanium coated bit just spun in place making a small dent. I used plenty of drilling oil. I tried two times and on the third attempt the drill bit glowed bright red. I switched bits, more oil, and still no luck. Finally I flipped the piece over and successfully drilled it from the other side.

    Did I do something wrong? Cheap mild steel had a hard spot? I probably hardened the spot with the heat.

    Is this common?

  3. #3
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    Re: Problem drilling mild steel flat bar

    Not uncommon. If dead set on entering that spot, I have had success spot annealing plate. Casting can be a real pain, I have had multiple boxes, where 50 from one lot drill fine, then none from another lot will drill.

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    Re: Problem drilling mild steel flat bar

    Quote Originally Posted by smithdoor View Post
    The flat bar may not be A36.
    Are you using scrap ?

    Dave
    Not scrap, I bought it at the local mill supply store. I never asked about the rating.
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    Re: Problem drilling mild steel flat bar

    Sounds like you work hardened that section with that bit not actually cutting. Sounds like the bit needed a re-sharpen. Before most every drill operation I do, I re-sharpen my drill bits. Get a drill sharpen gauge. I just use a protractor and set it at 55 degrees or so. You know the drill is cutting nicely when it cuts from both sides. If it is not, stop and re-sharpen using a tool.
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    Re: Problem drilling mild steel flat bar

    Quote Originally Posted by TJS View Post
    Sounds like you work hardened that section with that bit not actually cutting. Sounds like the bit needed a re-sharpen. Before most every drill operation I do, I re-sharpen my drill bits. Get a drill sharpen gauge. I just use a protractor and set it at 55 degrees or so. You know the drill is cutting nicely when it cuts from both sides. If it is not, stop and re-sharpen using a tool.
    Good point and I don't have a sharpener for my bits. I need one. Those bit are titanium coated so I bet any sharpening will remove that coating down to the base metal.
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    Re: Problem drilling mild steel flat bar

    What size bit? Speed? Hand drilling or drill press?

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    Re: Problem drilling mild steel flat bar

    New should be A36.
    Then I look at the drill bit .

    Dave

    Quote Originally Posted by Flyer58 View Post
    Not scrap, I bought it at the local mill supply store. I never asked about the rating.

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    Re: Problem drilling mild steel flat bar

    Skip those cheesy Chinesium-covered drills and buy better ones. Cheap tools, cheap results.

    Titanium coated? Yeah, sure thing.

    Or, buy a huge box of them from Crappy Tire and throw them away after each hole.
    Do not believe everything that you think.

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    Re: Problem drilling mild steel flat bar

    Coated shmoted. Don't let the advertising get you. Sharpen them as normal.
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    Re: Problem drilling mild steel flat bar

    I use a bench grinder, fine wheel. There are people on Youtube demonstrating the technique. I do it by eye only. I usually touch up any bit I intend to drill anything hard with.
    An optimist is usually wrong, and when the unexpected happens is unprepared. A pessimist is usually right, when wrong, is delighted, and well prepared.

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    Re: Problem drilling mild steel flat bar

    Quote Originally Posted by Willie B View Post
    I use a bench grinder, fine wheel. There are people on Youtube demonstrating the technique. I do it by eye only. I usually touch up any bit I intend to drill anything hard with.
    Willie, what's the smallest you can sharpen accurately?
    Over the years I've acquired (meaning found) a number of 'sharpening" tools (and some piles of dull bits too) and find problems with most of them, but have gotten most to work decently on larger bits. Anything under about 1/8" is difficult to do, to get both sides of a two-flute perfectly the same. Being somewhat creaky, I never got the hand method down as well as I'd like except for on large bits.

    To the OP; I second the other comments about the T. coating, if the bit wasn't sold be a genuine good company (e.g. Cleveland Twist Drill). Where did yours come from? Also, mild steel shouldn't be able to work harden. Could your bit have chipped badly when breaking through a previous hole, so was just rubbing, not cutting?

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    Re: Problem drilling mild steel flat bar

    Quote Originally Posted by Oldiron2 View Post
    Also, mild steel shouldn't be able to work harden.

    Could your bit have chipped badly when breaking through a previous hole, so was just rubbing, not cutting?
    OR,, when drilling the previous hole was complete,, could you have accidentally bumped the drill motor into reverse??

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  22. #14
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    Re: Problem drilling mild steel flat bar

    Correct mild steel should not be able to work harden but his bit glowed bright red on the steel. Hence now it is brittle and will drill like glass. This is like trying to redrill a hole that was cut by CNC plasma. Been there.
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    Re: Problem drilling mild steel flat bar

    Switch to self drilling screws. Then you just go through 20 screws on hard steel.

    Many years ago, The best change I made for drill bit longevity is controlled drill speed on larger bit and constant vertical pressure.

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  26. #16
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    Re: Problem drilling mild steel flat bar

    Hand sharpening bits under 1/4" is very hard to see if you have the right angle, relieve and the point centered. It's possible the steel the OP was drilling just had a hard spot right where he was drilling.

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    Re: Problem drilling mild steel flat bar

    Quote Originally Posted by tapwelder View Post
    What size bit? Speed? Hand drilling or drill press?
    3/16 bit on a drill press at 2030 rpm. and yes a cheap chinesium coated bit which cut other hole with little effort. Glowing bright red I half expected it to friction weld itself to the piece I was drilling.
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    Re: Problem drilling mild steel flat bar

    Quote Originally Posted by Oldiron2 View Post
    Willie, what's the smallest you can sharpen accurately?
    Over the years I've acquired (meaning found) a number of 'sharpening" tools (and some piles of dull bits too) and find problems with most of them, but have gotten most to work decently on larger bits. Anything under about 1/8" is difficult to do, to get both sides of a two-flute perfectly the same. Being somewhat creaky, I never got the hand method down as well as I'd like except for on large bits.

    To the OP; I second the other comments about the T. coating, if the bit wasn't sold be a genuine good company (e.g. Cleveland Twist Drill). Where did yours come from? Also, mild steel shouldn't be able to work harden. Could your bit have chipped badly when breaking through a previous hole, so was just rubbing, not cutting?
    Mrs. B got me a Christmas gift, a multi lens magnifier. I confess, I'm old. The size I'm limited to is dependent on sight. At 100 magnification somebody has to point me toward the grinder. At that point, the grit of the stone limits.

    In my world I drill somewhere over 1/8" first hole. Step up to 1/4". Then I start thinking about the flute minimum. Each step, I want the previous hole to match the flute diameter of the next bit.
    An optimist is usually wrong, and when the unexpected happens is unprepared. A pessimist is usually right, when wrong, is delighted, and well prepared.

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  31. #19
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    Re: Problem drilling mild steel flat bar

    I am a hand driller. I collect a few bits and some are a consumable and shat happens. They get brittle so to speak from stress and flex too but I actually get them from a flea vendor goes to huge trade exhibition show, been there yearly for decades and worth a visit. Saw a guy come just to buy a complete set but the grab bags are really good for general fab and love the 1 over sizes and 1 under for taps too but had some of them by the pound even and I look at my collection and I bought 10 pack of 17/64 and blow some paint in the baggie so I can recognize and buy 10 a time for some pilots. 1/8 is obviously used but I like 9/64 better, just a little stronger, some 3/16 too I buy some every hear, I sharpen a few, I dont take care of them but big difference when I get 25/50 holes from a bit I paid 1 dollar for is a deal. I drill dry, can of juice lasts me a long time, really brutal and punch and horse holes with a heavy duty battery drill.

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  33. #20
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    Re: Problem drilling mild steel flat bar

    Quote Originally Posted by Flyer58 View Post
    3/16 bit on a drill press at 2030 rpm. and yes a cheap chinesium coated bit which cut other hole with little effort. Glowing bright red I half expected it to friction weld itself to the piece I was drilling.
    Way too fast rpm in my opinion. I drill on lowest rpm on my drill press, which sometimes is too fast.
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  35. #21
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    Re: Problem drilling mild steel flat bar

    Quote Originally Posted by wb4rt View Post
    Way too fast rpm in my opinion. I drill on lowest rpm on my drill press, which sometimes is too fast.
    My thought as well... I've got my drill press down to 80 rpm and I like it there. I've also seen the titanium coated bits fail to drill right out of the box and the coating had to be ground off, but that doesn't sound like the case here since it wasn't the first hole. Spinning a bit that isn't cutting after the fluid starts to smoke ( you did use cutting fluid, right? Having said that I often cheat and use WD-40 instead... it smokes quicker so you stop sooner.) is just asking for trouble and won't drill any holes. I had one of those cheap bench mount sharpeners (utilizes the grinder) but all it did was teach me which angles to hand hold at. The small bits I just sharpen at a single angle and they seem to work fine.
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  37. #22
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    Re: Problem drilling mild steel flat bar

    I have a package of drill bits my father purchased in 1960's.
    Great looking
    But try drill soft steel they will glow red .
    They where low cost wood drill bits.

    Dave

    Quote Originally Posted by whtbaron View Post
    My thought as well... I've got my drill press down to 80 rpm and I like it there. I've also seen the titanium coated bits fail to drill right out of the box and the coating had to be ground off, but that doesn't sound like the case here since it wasn't the first hole. Spinning a bit that isn't cutting after the fluid starts to smoke ( you did use cutting fluid, right? Having said that I often cheat and use WD-40 instead... it smokes quicker so you stop sooner.) is just asking for trouble and won't drill any holes. I had one of those cheap bench mount sharpeners (utilizes the grinder) but all it did was teach me which angles to hand hold at. The small bits I just sharpen at a single angle and they seem to work fine.

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  39. #23
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    Re: Problem drilling mild steel flat bar

    Quote Originally Posted by Flyer58 View Post
    3/16 bit on a drill press at 2030 rpm.
    According to my drill speed chart, you want about half that speed for 3/16" bit on MS.

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  41. #24
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    Re: Problem drilling mild steel flat bar

    I did use cutting fluid, which I called oil earlier, and set the speed based on the decal on the drill press. The metal is actually 1/8 mild steel but my handy dandy thickness gauge is in decimal and gauge. I'm totally sold on the idea of getting a sharpener or at least watching a few videos about how to resharpen the bit I have. I appreciate everyone input

    Drill press recommended RPM:

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  42. #25
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    Re: Problem drilling mild steel flat bar

    I think Tubalcain said in one of his vids. If you can't see the flutes you are too fast. I do most of my drilling on my Bpt Mill. I use that rule and seems to work great for me.
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