Why won't a cobalt 1/2" bit drill this mild steel? - Page 4
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  1. #61
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    Quote Originally Posted by tdmidget View Post
    I guess that is why some of them are still making money for their owners 50-70 years later? Ultra sound does not tell you that it is "rotten to the core". It measures to the first interruption, be it crack, void, whatever. The old timers took all that into consideration. Here's a test for the new shit. Weigh the parts.
    Just pointing out that a "solid iron" casting is not necessarily a better casting. The ultrasound showed a void in the middle some castings no matter where you placed the ultrasound probe. The iron foundry were aware of these issues but if it doesn't affect operation and it's not visible, then why bother redesigning the pattern?. This mainly applies to "old iron" pre WW2 or older when casting was an art, not a science. One solution is to make hollow castings so shrinkage is less of an issue. It's a common problem in the foundry game and a hollow casting not only solves the issue, it saves a lot of materials and weight and time taken for the castings to cool in the mould. You don't see any big lathe beds made from a solid block of iron, do you?.

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    Quote Originally Posted by SAG 180 View Post
    This mainly applies to "old iron" pre WW2 or older when casting was an art, not a science.
    Given that my older metallurgy texts were Dad's from his University years, 1926 onward, I'd have to differ. Wrong War.

    This s**t was more science than art before the Spanish American War. Niles Tool Works, Bement, Pond, Gray, and a host of other Heavy Iron gurus grew up starting around the time of the Civil War. The US one, not the English ones.

    Iron cannon vs better but costlier Brass and Bronze had been the get-it-right-or-die motivator for heavy sections. Iron cookware, farm, and commercial goods the perfectionator of thinwall sections.

    Yes, the craftsmen were experienced. No, they were not just guessing in the dark.

  3. #63
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    Any time your drill makes those unpleasant sounds,your speed is MUCH TOO FAST. You very possibly have ruined the tip of the cobalt drill,and it needs re grinding. There is nothing like chattering that will take the sharp edges off more quickly.

    You need to make the speed MUCH SLOWER.

    This is as simple as I can say it. I have drilled many a 1/2" hole with my 1963 Craftsman drill press. It DOES have the high-lo speed attachment they sold back then. I can get anything from crawling speed to 10,000 RPM with it. It's just a 3rd pulley,mounted in the column of the drill press.

    Now,I do have a much larger drill press,but in many years past,the Craftsman did just fine.I bought it new in 1963,when I was just starting to get a shop of my own together.

    You DO need to tighten up the belt on your machine. Get a can of "Belt Traction" and spray it on BOTH sides of the tapered part of the belt-the parts of the belt which actually do the pulling! It will be very slippery till it dries,then will pull like a maniac!

    You really don't need a COBALT drill to do that job. A HSS drill would do just fine if used correctly at a much slower RPM. Indeed,a CARBON steel drill bit lubricated with SOAPY WATER is what the British used to drill holes in THICK armor plate back in the 19th. C. You just have to run the drill SLOWER. Very slow for carbon steel. People who knew how to get jobs done have been getting them done for HUNDREDS of years with know how.

    As a last thought,some steels will harden when welded. That object you're trying to drill is welded together. Your hole is not too far from a weld. Or possibly a cutting torched area,which would also harden some steels. However,either before or after welding,someone drilled and tapped a hole near where you're trying to drill. But,I'm certain that you just need to go at a much slower RPM,and hope the cutting edges of your drill haven't been dulled. If no luck,just try a HSS drill at a very low RPM. Sick a chain saw file into the 1/4" hole,and see if it WILL FILE the steel.That won't mess up the paint.

    P.S.: You did not mention the BRAND of cobalt drill you have. Hopefully it isn't CHINESE.
    Last edited by gwilson; 08-12-2017 at 01:43 PM.

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    Quote Originally Posted by gwilson View Post
    P.S.: You did not mention the BRAND of cobalt drill you have. Hopefully it isn't CHINESE.
    If it was made in the last ten or so years, that part is almost guaranteed, George.

    Bassett | Chicago-Latrobe | Cleveland | Cle-Line | Cle-Force | Greenfield

    And more, globally, are all part of Dalian Top Eastern. TDC is the world's largest maker of drills, make their own steels and carbides.

    The Chinese did at least buy new and better equipment for the old-line US drill makers when they took them over. Been covered already. Right here on PM.

  5. #65
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    Quote Originally Posted by dbooksta View Post
    Well ... I can feel a ridge around the dent with my finger, but it's not what I would call a visible ridge:

    Attachment 205464
    That looks like a center punch mark put in to abrasion resistant steel.


    Sent from my iPhone using Tapatalk

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    cobalt , tIN , m7, CARBIDE , whatever ....... great for high production in a cnc machine, but for most jobs ,even
    the lowest economy hss drill will poke a hole just fine . for something like a clearance hole for a capscrew or
    a plug weld .. who gives a piss if it is .005 over .

    i prefer cheap hss because it is easy to grind. takes less than a minute ... try that with a chunk-webbed m42 ?

    i'd have to dress the grinding wheel, then abuse the edge of the belt on the 6x48 rockwell grinder to split the tip...

    m-2 , a few passes on the belt .... usually don't even have to bother to cool the thing.

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    Quote Originally Posted by tnmgcarbide View Post
    cobalt , tIN , m7, CARBIDE , whatever ....... great for high production in a cnc machine, but for most jobs ,even
    the lowest economy hss drill will poke a hole just fine . for something like a clearance hole for a capscrew or
    a plug weld .. who gives a piss if it is .005 over .

    i prefer cheap hss because it is easy to grind. takes less than a minute ... try that with a chunk-webbed m42 ?

    i'd have to dress the grinding wheel, then abuse the edge of the belt on the 6x48 rockwell grinder to split the tip...

    m-2 , a few passes on the belt .... usually don't even have to bother to cool the thing.
    Agreed...slow & steady and even the cheapest drill bits cut as long as the geometry is correct.

    But I still say that's AR steel, and if you try to speed thru it, it just eats your edge off.


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    Where's John Welden in all this? I miss the guy. He would of commented for sure, you need CNC.
    All kidding aside, I think the OP is asking this question on the wrong forum. Professional machinists trying to teach a layman????

    Come on.....

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    Here is my Welden impression:
    A cobalt 1/2" drill will drill mild steel if you don't use retarded techniques. You should post this on a home shop site, not this one.

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    You need to work on that. Per Weldon , he would be a "Hobbytard".

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    Quote Originally Posted by tdmidget View Post
    You need to work on that. Per Weldon , he would be a "Hobbytard".
    While copying is the sincerest form of flattery, I believe
    Cellardoor can only be refered to as "John Weldon Light"....

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    For over 100 years machinists have been drilling tough tool steel with low quality carbon steel drills, not even hispeed steel drills much less cobalt drills.The simple answer to his problem is way way to fast rpm and much to little pressure.Once you drill even the mildest of steel for a few seconds at 1000 rpm and don't have any penetration, the game is over. You have work hardened your part and have a flat on your drill edge. Resharpen your drill,slow way down and try to bust thru the glaze. All you have to do is look at your drill and your hole with a magnifying glass. If this isn't obvious to you, maybe find a different hobby. Edwin Dirnbeck

  15. #73
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    Quote Originally Posted by Mike1974 View Post
    Years ago i ran a big Carlton that we had up to 3" drills for. Clamp the sh*t out of your part, engage power feed on a 3" drill and stand back in awe.
    Something really satisfying about watching chips the size of a mans arm spiral effortlessly from steel.

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    Yesterday I was poking a 3/4 inch hole though four inches of some unknown steel round.

    After pre drilling with a 3/16ths drill, I set out with the 11/16 ths drill prior to reaming ( I know a hefty chunk to ream.

    At 960 rpm, the large drill was smoking and burning the canola oil I use for ferrous work. I worried about the drill edge, and nudged the VFD down a notch at one point.

    The burned oil is enough to suggest a slower surface speed. ;-)

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    Quote Originally Posted by manualmachinist View Post
    Something really satisfying about watching chips the size of a mans arm spiral effortlessly from steel.
    ..On You-tube, surely.

    Otherwise?

    Guess you have never spent 8 hours at a go DODGING even their baby brothers off a 50-inch Niles, fifty Mike Foxtrot Dee Cee for-real-not-for-AC-nameplate horsepower.

    "Satisfying" was grinding 3/4" worth of Crucible's good Rex 95 so they broke-up well enough you could clock out without too-damned many new burns and near-zero blood.

    Nothing "effortless" about cranking that massive carriage back to start, either.

    No rapids.


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    Quote Originally Posted by tdmidget View Post
    You need to work on that. Per Weldon , he would be a "Hobbytard".


    Yeah and not even one F word.

    Regards Tyrone.

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    Quote Originally Posted by tdmidget View Post
    You need to work on that. Per Weldon , he would be a "Hobbytard".
    I guess the years I've spent as an instructor are speaking for me, but I'd rather have someone come here who can learn from the old farts instead of getting nonsense from his fellow ignorants.

    From his follow on posts the OP did "fix" what was wrong and got the hole done, so that's progress. Even posted separately about the gloves, which again points to wanting to better understand why it's a bad idea to wear them in most machining contexts.

    We are, collectively, reducing entropy in this world. I'd call that a good thing.

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  21. #78
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    Quote Originally Posted by edwin dirnbeck View Post
    For over 100 years machinists have been drilling tough tool steel with low quality carbon steel drills, not even hispeed steel drills much less cobalt drills.
    True enough, but here's another thing practically forgotten from the tricks of about 100-plus years back. Only ever worked with it the ONE time, but Herr Pelz had himself had the benefit of training under superb masters, became another, and an excellent teacher himself. He made sure the old arsenal of tricks was conveyed, whether still of best use or not.

    Paraffin wax. Coat the part. Expose a target area. Apply Nitric Acid, Technical grade.

    Successive goes can put a reasonably well controlled hole though harder and thicker steel, and faster, than you might expect. Nasty stuff, strong Nitric Acid. But it got the job done.

    Bulk of the material out of the way, there was always an abrasive that could then clean that hole up to desired shape and size, no matter how hard the metal.

    And then there are torches. Plus abrasives, again.

    Drills.. .are NICE.. even more so if one understands the tedium of the alternatives.


  22. #79
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    Nitric acid,I BELIEVE,is not so easy to buy these days. Can be used in bomb making,I suppose. I could get any chemical I wanted by having the museum order it. But not so easy for an individual.

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    Quote Originally Posted by gwilson View Post
    Nitric acid,I BELIEVE,is not so easy to buy these days. Can be used in bomb making,I suppose. I could get any chemical I wanted by having the museum order it. But not so easy for an individual.
    "Not so easy" is perhaps the understatement of the whole year, yes. Sets off alarm-bells, Museum or no.

    OTOH those of us "in the record" for our background with loud ringing noises in the ears are good with that.

    And we CAN buy solid-carbide drills! Waaay easier on the lungs, those are.



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