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    Default Bronze

    Hi all. I've got a project going involving boring a hole down the middle of a bronze bar, 3" OD. The material is alloy 630 Ni/Al/Bronze.

    The issue I'm having is that the drills are having a harder time than I expect getting through this thing. I started with 1/8", which worked ok, but when I went to 1/4", I got a lot of binding. I made sure the bit was plenty sharp, but I'd go about 100/200 thousandths, and lathe would slow down, start spinning the bit in the chuck, etc. I had to keep backing it out to clear (not very many) chips, and restart. After I got through it, I went to 3/8", and got the same thing.

    I'm pretty sure my drill bits are in good shape, I've used them doing similar things in steel and aluminum with no trouble. It seems like there's something different about this material which is fighting me.

    Any hints welcome.

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    It's not binding per se, it's "grabbing" at the chisel edge. You need to dub the drills you'll be using after the initial one so they don't grab.

    Spare parts #7 - Modifying A Twist Drill For Drilling Brass - YouTube

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    I’d suggest a very hard tool, carbide. This alloy contains 4 to 5.5 percent of nickel and 2 to 4 percent of iron, a tough combo. Cut at around 80 m/min or 260 sfm.

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    Dubbing the drill helps a lot on bronze and brass. Don’t bother with the pilot hole. If you need a stepped hole, run the bigger drill first.

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    Quote Originally Posted by Spruewell View Post
    ..run the bigger drill first.
    And FORGET any advice you hear about "Brass". Or even ignorant Tin-Bronze.

    Nickel-Aluminium-Bronze is "special". VERY!

    Go read-up and Learn all about it.

    Not new. The experts have shared. "Right here, on PM", too.

    Or order-up spare ass right along with replacement tooling and re-grinding services.

    It does not take prisoners. Only economic slaves.
    Get it right? You can grow to love it!

    Well.. it was more socially acceptable that crawling sado-masochistic hoorhouse floors under a bloody whip?

    Or so the grown-ups claimed! Whom was I to risk the alternative?
    I chikn'ed out ...and learnt the Bronze!

    Sure 'nuf. The scars were smaller and cheaper!

    As far as I know....


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    usta drill wear plates for body dies,the square post type."guide post"instead of guide pins.
    if you look at the way the chip flows when it leaves the cutting edge,its up hill rite?
    so if you grind the cutting edge so the chip is going up a straight wall,or cliff you can drill bronze for 12 hrs on nite shift,no problem. most of these holes were 9/16,clear for 1/2 shcs. we also tapped some with what we called staggered tooth taps.
    good luck,lose the pilot drill too,maybe.
    Gw

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    Lot's of good info. I'll try "dubbing" a drill and see how that works. And continue reading.

    Thanks!

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    Also use new drills, .............they should be ground with a small back taper, ........which soon wears away drilling steel and iron etc etc.

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    Quote Originally Posted by jrd-sb View Post
    Lot's of good info. I'll try "dubbing" a drill and see how that works. And continue reading.

    Thanks!
    Good start. Learn it's peculiar ways? It's just another arrow in your quiver.

    Looks like brass? Or one of the OTHER, easier, Bronzes?

    That sorta "traps" folks at first.

    "Traps" taps even worse than drills, too!

    Wait and see!

    FWIW? PM has some guys SERIOUS masters of it. Better sharing of the lore than any book, and I have a ton of 'em.

    Become one of those masters.

    Dull day, yah can kinda smirk when some newbie figures it for no-drama brass, has it eat his drill.

    Then won't even give it BACK!!


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    First tip - use meaningful thread titles. I was expecting to see a thread on naked lady statues made out of bronze. WTF?

    Second tip - provide useful information. How big a hole? How deep?

    Third tip - i got nothin'

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    I don't know the full mechanics of why, but it always seems like the drills are grabby if you use a pilot hole. Probably because the drill is too aggressive with the center missing but not sure. Dubb the drill and don't drill a pilot hole as was mentioned and I think it will improve measurably.

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    Quote Originally Posted by crossthread View Post
    I don't know the full mechanics of why, but it always seems like the drills are grabby if you use a pilot hole. Probably because the drill is too aggressive with the center missing but not sure. Dubb the drill and don't drill a pilot hole as was mentioned and I think it will improve measurably.
    ANY material, conventional helical twist drills want a sub-web-thickness pilot or none at all. Hard to centre-pivot on ignorant air.

    BAD habit to use helical twist drills as if they were progressive reamers to "open up" a hole. Wrong geometry for the job. 'loominum might allow it. Nickel-Aluminium-BRONZE is far less easily amused.

    They don't TEACH this s**t any longer?

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    what Limy said.
    Backtaper your drill and the problem will go away

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    "the Bronze kill our pride"

    Sorry, couldn't resist that quote from Mad Max after reading the title.

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    Followup: Yep, dubbing did the trick. It's still some work for my little SB9 to chew into that thing, but it no longer binds, and the chips coming out look much more sensible.

    Thanks again.

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    Quote Originally Posted by Scottl View Post
    "the Bronze kill our pride"

    Sorry, couldn't resist that quote from Mad Max after reading the title.
    Love it. One of my favorite movies

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    Quote Originally Posted by crossthread View Post
    I don't know the full mechanics of why, but it always seems like the drills are grabby if you use a pilot hole. Probably because the drill is too aggressive with the center missing but not sure. Dubb the drill and don't drill a pilot hole as was mentioned and I think it will improve measurably.
    Huh. Understood but slightly confused. (and this is off topic of my original post) My (now deceased) machinist buddy taught me that when boring a biggish (like bigger than 1/4") hole in something, I'm better off to go with a pilot hole, then enlarge, rather than try to get all the way to my final diameter in one go. What I remember from his explanation was that the larger drill bits will do a better job if they're not trying to chew up the center while simultaneously removing all that material out near the perimeter. Of course, he was working in steel and aluminum, and as I'm learning, I can't expect materials to behave the same way. Does that make sense in this case?

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    Quote Originally Posted by jrd-sb View Post
    Huh. Understood but slightly confused. (and this is off topic of my original post) My (now deceased) machinist buddy taught me that when boring a biggish (like bigger than 1/4") hole in something, I'm better off to go with a pilot hole, then enlarge, rather than try to get all the way to my final diameter in one go. What I remember from his explanation was that the larger drill bits will do a better job if they're not trying to chew up the center while simultaneously removing all that material out near the perimeter. Of course, he was working in steel and aluminum, and as I'm learning, I can't expect materials to behave the same way. Does that make sense in this case?
    He wasn't really a machinist, then.

    The progressive opening-up is valid where you do not have the proper machine-tool and power for the job.

    The helical twist drill is the right tool for the initial "virgin ' hole.
    It is the WRONG tool to ream it larger.

    Twist drills and spade drills rely on that center divot for guidance to geometrically "generate" a round hole. It ain't THERE no more. GONE!

    Try it with a hand power tool and Irwin Speedbore bit on WOOD. Make a half-inch hole. Speedbore again and open it up to one-inch? Or try it With a "brace" and Auger bit? You KNOW BETTER, yah?

    You have a pilot HOLE? Now you need a pilot to follow it. A piloted counter-bore tool may serve. Even a shop-fab "D" reamer piloted to your existing bore. You did say SB Nine? Small stuff. Just make what you need. Its quickly done.

    If no pilot?

    What you want to enlarge a now EXISTING hole is a "core" drill, a "plunge" endmill, a "balanced" boring bar,

    Or "similar".

    Boring capability that does NOT rely on the absent center material for guidance.

    That basic. ANY material.

    Lathes are better at boring than they are at drilling anyway.

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    Quote Originally Posted by thermite View Post
    He wasn't really a machinist, then.
    Ummmm. With respect: he worked as a machinist and maintenance officer for the USN for years; when he got out, he was the foreman in two machine shops and owned a third. He did aircraft restoration, including a lot of parts fabrication, on dozens of warbirds. I've found most of his advice over the years to be spot on.

    I'm willing to believe that I misunderstood him in this case. What you say makes sense, especially about how if I have a pilot hole, I'm better off with something to follow it that relying on a twist drill, which won't really.

    I should also point out that my goal with this thing is to get a hole big enough that I can take it out to its final diameter with a boring bar. So I think I don't care hugely about keeping the hole precisely on center at this point, as the boring bar will tend to correct it. Am I wrong?

    I also take your point about the SB9 being too small for this job. Granted. I'm willing to take my time with it.

    In my assorted tools I have some piloted reamers. I think my next pass will be to find one with the right size pilot, or make such a thing, then use that.

    Anyway, I sincerely thank you and everybody for your input. Lots more listening and learning to do. Apologies in advance for my naive questions.

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    Quote Originally Posted by jrd-sb View Post
    Ummmm. With respect: he worked as a machinist and maintenance officer for the USN for years; when he got out, he was the foreman in two machine shops and owned a third. He did aircraft restoration, including a lot of parts fabrication, on dozens of warbirds. I've found most of his advice over the years to be spot on.
    We all have our favourite blind spots. Bad habits as well.

    ALL of us. One of mine is to be forever riviting s**t where others would tap and thread. Take it apart? Why? And even if so, just drill it. Too lazy to weld, Iyam!

    Other among us would TiG the crack of Dawn, only lend her an angle-grinder for the loo if she hadn't been a nag that day.

    that I can take it out to its final diameter with a boring bar.
    Life is easier if you have a larger clearance hole before you have to hit a too-damned-light boring bar with Iron deficiency anemia carriage on a spaghetti bed under it, yes.

    I just use a drillpress for that whenever possible.... even on FAR heavier lathes.

    If nothing else, a DP clears chip better and faster. Go figure they were intentionally designed to make holes?

    Kind of an aferthough on a lathe, "drilling" is, so they tend to do it badly.

    Unless .... given special help to set them up FOR it with other than a one-hole handwheel-operated tailstock.

    Ram lever, capstan, turret, powered on the carriage, or powered second carriage, "etc"... and see also "gun" drilling rigs.

    "Tooling, tooling, tooling"


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