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Thread: Problem drilling mild steel flat bar

  1. #76
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    Re: Problem drilling mild steel flat bar

    Quote Originally Posted by 52 Ford View Post
    Well... guess there's one way to find out! You go ahead and buy me a set of them, I'll use them till they're dull, then try and sharpen em.

    I prolly could touch one up if I was in a pinch. I've turned regular drills into split points with a sharp corner on a bench grinder and a set if diamond files.

    Look up "hyper step" drills. It's a twist drill, but the point is ground in steps (like a normal step drill). They're supposed to be pretty great.

    Actually, here's a link to some. Apparently "hyper step" is just a sorts generic term for them.
    https://www.amazon.com/Norseman-2290...77678630&psc=1

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  3. #77
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    Re: Problem drilling mild steel flat bar

    Quote Originally Posted by farmersammm View Post
    You do realize that these kind of bits, with the 3 flutes, were originally designed to widen holes. It's very hard to find them anymore. I'd like to have a decent set of the diameters I work with the most.

    And..........."cobalt" is just a sales gimick to sell HSS. Sorta like Titanium, or other coatings/additives. In the end, it's the sharpened HSS cutting edge that does the work.

    Regular HSS, off the shelf, is plenty hard to drill anything but steel that's harder than HSS.
    Provided it's kept sharp.

    The relief angle is key to the deal. The sharper the angle, the better it cuts. It will actually suck its way down into the steel. Kind of like a plow. On the flip side, the cutting edge will decay much faster. But if you have a bench grinder, it's not an issue. Takes about 3 minutes to sharpen a bit. I came to this the hard way. I got tired of throwing out bits when they got dull. Found that the drill bit sharpening machines are mostly junk.....................bought a General Hardware drill bit gauge, and never looked back. You can virtually get a lifetime out of most any drill bit, if you learn to sharpen it freehand.
    Sammmm, it's not that simple. The "tool steel" category has a good variety of formulations, each having different properties and thus different uses, particularly in production where changing tooling slows the whole process. Wear can be the very gradual removal of the metal (atoms), or fine but slow chipping, or catastrophic breakage. Besides price (not shown), the table below demonstrates these different properties.

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  5. #78
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    Re: Problem drilling mild steel flat bar

    Quote Originally Posted by Oscar View Post
    But can you sharpen a 3-flute cobalt drill bit with all the relief angles?!?

    Only three?
    I have no idea what this is for. It came in a box of bits and fittings I bought at an auction. Countersinking? I paid $4 for the collection and it included a small box with $5 in coins.

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  7. #79
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    Re: Problem drilling mild steel flat bar

    Yes, that is a countersink. Depending upon what it is made from, it may do well on wood and aluminum, but not so well on steel
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  9. #80
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    Re: Problem drilling mild steel flat bar

    Quote Originally Posted by Flyer58 View Post
    Only three?
    I have no idea what this is for. It came in a box of bits and fittings I bought at an auction. Countersinking? I paid $4 for the collection and it included a small box with $5 in coins.

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    Yea, that's not a drill bit, it's a counter-sink bit
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  11. #81
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    Re: Problem drilling mild steel flat bar

    Cheap counter sinks work well for deburring holes. Pop them in the cordless drill and give them a couple rotations to clean the edges up.

    The hardened ones for cutting steel and stainless chip too easily when using them to quickly deburr holes.
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  13. #82
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    Re: Problem drilling mild steel flat bar

    I like a step drill for cleaning.

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    Re: Problem drilling mild steel flat bar

    Titanium Nitride coatings are an anti-wear coating and certainly are not a gimmick, and when it comes to cobalt, Cobalt is a very hard, brittle tool and will hold up well if handled and used properly, they won't take flexing because they''l break. Our shop ordered all of our end mills and carbide insert tools with the TIN coating, it allows faster cutting speeds and last longer.

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  17. #84
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    Re: Problem drilling mild steel flat bar

    When you you sharpen bits with coating what happens to the coating?

  18. #85
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    Re: Problem drilling mild steel flat bar

    Quote Originally Posted by CAVEMANN View Post
    Titanium Nitride coatings are an anti-wear coating and certainly are not a gimmick, and when it comes to cobalt, Cobalt is a very hard, brittle tool and will hold up well if handled and used properly, they won't take flexing because they''l break. Our shop ordered all of our end mills and carbide insert tools with the TIN coating, it allows faster cutting speeds and last longer.
    AlTiN is supposed to be even better than TiN. I have no experience with it. You can't use it on Aluminum, though.

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    Re: Problem drilling mild steel flat bar

    Quote Originally Posted by tapwelder View Post
    When you you sharpen bits with coating what happens to the coating?
    It goes away. BUT, it's still on the flutes. Keep in mind, you're only removing material on the RELIEF side if the cutting edge. So, the areas that are actually having swarf rub on them are still coated.

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  21. #87
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    Re: Problem drilling mild steel flat bar

    Just finished a 60 hour welding course. Instructor was 30 year welding veteran. Same thing happened with our A36 steel. He said we’re only getting cheap Chinese steel, which contain recycled steel. He said they may melt-down a crankshaft or other hardened steel in the mix, which you are hitting.

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  23. #88
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    Re: Problem drilling mild steel flat bar

    Quote Originally Posted by BigAl22 View Post
    Just finished a 60 hour welding course. Instructor was 30 year welding veteran. Same thing happened with our A36 steel. He said we’re only getting cheap Chinese steel, which contain recycled steel. He said they may melt-down a crankshaft or other hardened steel in the mix, which you are hitting.
    Alloys should be added in measured quantities and the changes tested to see the resulting product, screw-ups can be reformulated to get the proper carbon ratio, if it's not getting that quality control then the end user is getting screwed. I don't know about modern steels, but Chinese QC has improved on most things, if it hasn't improved on steel, then they're producing bed-rail crap.
    Going back to the original problem, I've had success turning the piece over and tackling it from the back side, but have never had it happen with mild steel, only stainless which is horrible for work hardening if you ever let a bit dwell in the hole without cutting. I also wonder if the OP had a very dull bit that got so hot that it transferred alloy into the hole.
    Last edited by CAVEMANN; 08-13-2022 at 11:07 PM.

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  25. #89
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    Re: Problem drilling mild steel flat bar

    Quote Originally Posted by CAVEMANN View Post
    Alloys should be added in measured quantities and the changes tested to see the resulting product, screw-ups can be reformulated to get the proper carbon ratio, if it's not getting that quality control then the end user is getting screwed. I don't know about modern steels, but Chinese QC has improved on most things, if it hasn't improved on steel, then they're producing bed-rail crap.
    Going back to the original problem, I've had success turning the piece over and tackling it from the back side, but have never had it happen with mild steel, only stainless which is horrible for work hardening if you ever let a bit dwell in the hole without cutting. I also wonder if the OP had a very dull bit that got so hot that it transferred alloy into the hole.
    I did the OP and the first bit was used and might have been slightly dull but had just cut through 4 holes without any problem. When I got to hole #5 it just stopped and spun. I wore out a second sharp bit in the same hole and then a third bit went through after I flipped over the metal and drilled through a small crack where the others had stopped short. The second and third bits were sharp when I started. The first bit was totally rounded off.

    The remaining 3 holes were easily drilled out. I think they were 1/4 in holes and bits #2 and #3 were slightly smaller. I did hit a starting dimple to mark each hole location before drilling and to center the bit.

    It's seemed like that one spot had a harder metal mixed in yet looked the same after removing the mill scale.
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    Re: Problem drilling mild steel flat bar

    Technically it not A36 steel . But I can see Chinese giving bad steel.
    Recycled steel has been around for over 100 years but mill would bring back to sepc.

    In my line work if I purchased A36 it had to meet A36 specifications and have paperwork from mill showing it does.

    Dave

    Quote Originally Posted by BigAl22 View Post
    Just finished a 60 hour welding course. Instructor was 30 year welding veteran. Same thing happened with our A36 steel. He said we’re only getting cheap Chinese steel, which contain recycled steel. He said they may melt-down a crankshaft or other hardened steel in the mix, which you are hitting.

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  28. #91
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    Re: Problem drilling mild steel flat bar

    Quote Originally Posted by farmersammm View Post
    Regular HSS, off the shelf, is plenty hard to drill anything but steel that's harder than HSS. Provided it's kept sharp.
    Yep, I've had better results using regular plain old vanilla HSS bits than anything else...

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