Feeds and Speeds for 1/8" Parabolic Drill - I keep breaking them
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    Default Feeds and Speeds for 1/8" Parabolic Drill - I keep breaking them

    Hello,

    I hope someone can give me some advice.

    SPECS:
    Haas VF4-SS, 6061 Aluminum, Flood Cooling
    Chicago Latrobe 120DHT Parabolic drill, depth of 2.3 inches


    I bought a company that makes a product that has been in production for quite a while. I am a one man show at this point. Somewhere on the order of thousands of parts already made, 160 or so by me.

    We are drilling 8x holes per part at a depth of 2.3" deep, approximately. Accuracy only matters for the top 1" or so, and even then the tolerance is not all that important. We spot drill first and are using Chicago Latrobe 120DHT 1/8" parabolic end mills. Historically these have been drilled at 6112 RPM at 24IPM (200 SFM, .004 IPR) with a 0.75" peck drill. Since I have taken over the company (one man shop) I have cycled 160 or so units without changing out the bit, until recently when the installed bit broke. After the 1st breakI replaced it and the new one broke on the 1st hole. I replaced it again and got 5 holes out of it. Replaced again and broke on the 2nd hole. I have tried reducing my speeds and feeds to be as safe as possible with no luck.

    I have reduced my SFM to 150 which is 4584 RPM and and a IPR to .002 but still broke. I get a lot of squeaking on the plunge. Any ideas? Tired of making scraps! Those broken bits don't come out and my oops pile (wall of shame) is growing and more importantly I'm out of production at the moment.

    Thanks in advance!
    Alex

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    Driving a 1/8" drill 2.3" deep will cause chip packing for sure:

    "Softer materials are best drilled with a deep hole parabolic (narrow lands, wide flutes for extra chip space) design. These drills are normally used to 14 diameters without peck drilling and are available with 118 or 135° split or notched points." This is from the 2013 Chicago-Latrobe catalog item for their parabolic drills, section titled "Deep Hole Drilling".

    14/8= 1.75"

    You need to peck at least once, and twice would be safer.

    If this is too slow, you'll need something like a coolant-through drill fed at high pressure, to force the chips to flow out, preventing packing.

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    Check your runout at the tool tip. Make sure you have the exact replacement drill. If I recall, CL have a few types of parabolics with similar names.

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    Sounds like lower receiver woes... I agree, check and make sure you have the right drill. Then make sure you have correct coolant pressure. If the setup ran holes with no issues previously, something changed.

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    I think your peck is to deep .75 sounds deep can you turn down the drill bit just past the tip to give the walls some room. I have a buddy who deep drills Aluminium he uses something called missle lube I don’t know what it is but he drills smaller holes then that deeper then that with missle lube
    Don


    Sent from my iPhone using Tapatalk Pro

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    Quote Originally Posted by eKretz View Post
    Sounds like lower receiver woes...
    The force is strong with this one! The first two I broke after the initial were the exact same. The only difference in the new ones are they are TiN coated. So far I have only broken one of the new ones...but only have tried to cut two parts. My last run was successful, I will post more soon.

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    I would use bright over TIN in aluminum any day of the week, and weekends too.
    Dave

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    Quote Originally Posted by D Nelson View Post
    I think your peck is to deep .75 sounds deep can you turn down the drill bit just past the tip to give the walls some room. I have a buddy who deep drills Aluminium he uses something called missle lube I don’t know what it is but he drills smaller holes then that deeper then that with missle lube
    Don


    Sent from my iPhone using Tapatalk Pro
    This is what I am looking at next, the peck drilling.

    The last one I broke I was at S4500 F10 and a peck depth of .5in. Broke 1st hole.

    I put a new bit in and tried the following: (simplified)

    S6071 M3
    G83 Zx.xxx R-x.xxx Q0.125 F30
    Seems to work good, but I get a squeak around the 4th to 5th peck. Deeper it's quiet, and the first few pecks are quiet. But not breaking is good. Not breaking, no squeaks to make me nervous, and faster would be better.


    Read online about the 3-2-1 method, so I'm going to give that a try.

    Next cycle this is my strategy: (again, simplified)

    S6071 M3
    G83 Zx.xxx I.375 J.125 K.125 R-x.xxx F30
    3/8" peck the first time, 1/4" the next followed by .125" pecks.

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    Quote Originally Posted by 13engines View Post
    I would use bright over TIN in aluminum any day of the week, and weekends too.
    Dave
    Interesting, can you explain why? I am trying to learn this.

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    Quote Originally Posted by crane550 View Post
    Historically these have been drilled at 6112 RPM at 24IPM (200 SFM, .004 IPR) with a 0.75" peck drill.
    .
    .
    After the 1st breakI replaced it and the new one broke on the 1st hole. I replaced it again and got 5 holes out of it. Replaced again and broke on the 2nd hole.
    .
    .
    I get a lot of squeaking on the plunge.
    It is trying to TELL you something, yah?

    Chicago Latrobe 120DHT Parabolic drill, depth of 2.3 inches
    ..
    ..
    Chicago Latrobe 120DHT 1/8" parabolic end mills.
    Can't BOTH be right...

    Ain't running the Mother-f**ker in REVERSE or using wrong-rotation tooling perchance, are ye?



    Using CTD HSS-Cobalt parabolics "all manual" early 1940's Walker-Turner, since.. 1974 or so? Lovely drills. REALLY lovely.

    CAVEAT: Those were made in USA.

    Your "Chicago Latrobe" may or may not be.

    The Chinese owner is part of Dalian Top Eastern. Some of their factories are still in the USA, Chinese owned, US staff. Other factories are in China.. Europe.. etc..

    GFI | About Us

    Strange things are afoot with China, these days...

    It could be a dice-roll which source, and tip grind is crucial to chip-forming and everything else.

    Might want to look at Guhring, Triumph or such?

    BTW... Helical TWIST DRILLS, not plunge endmills. There IS a difference. Bigtime.

    My "peck" equivalent is almost never more than 1/4" in gummy shiney wood or steel, either one. Mainly 'coz I dislike shiny wood, treasure the drills and am a serious-cheap bastid.

    Do that - clearing 3 or 4 times as often - right away. The CNC high-speed idiot won't get tired, you'll buy yerself some leeway, and you may be back into production soonest, even if at a skosh longer cycle-time per hole.

    THEN see if your supplier has changed alloy or heat, fixture is moving, coolant has gotten crazy glue into it ...spindle has gone full of beach sand ...or just "WTF?"...

    .. 'coz SOMETHING has surely changed to make such an EXTREME difference.

    Totally off-the wall difference.. 160 units * 8 holes each = 1280 holes on ONE tool, suddenly down to one to five holes per tool?

    Not the same tip grind, not the same CNC code, not the same tool at all you THINK you had/have, first, chip-bind second, unwanted movement during the operation third are the highest on MY list.

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    How's your coolant? You said you took over the business, did it sit for a long time? Is it fresh or old? Concentration? Different brand or type?

    Sent from my SM-N960U using Tapatalk

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    Quote Originally Posted by cb750chris View Post
    How's your coolant? You said you took over the business, did it sit for a long time? Is it fresh or old? Concentration? Different brand or type?

    Sent from my SM-N960U using Tapatalk
    Changed it out two months ago. I have a refractometer, I will check it tonight and see where we are at with it.

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    Quote Originally Posted by thermite View Post
    Can't BOTH be right...
    You are also right! I misspoke, there is no end mill just a parabolic drill. It's late, too many hours working!

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    Quote Originally Posted by crane550 View Post
    You are also right! I misspoke, there is no end mill just a parabolic drill. It's late, too many hours working!
    I picked up a trick ten years, watchmakers on staff. "Watchmakers" eye loupe. Simple creature. monocle with a clock-spring headband so both hands are free.

    Esslinger.com - Not Found

    Aim one of those at your drill tip grind. "8X" is a good sweet spot. Some other source should have them.

    Bad grind is obvious as sin when drills DON'T. (drill...)

    And we've MOSTLY skipped right past it off the back of TRUSTING what USED TO BE one of the several legendary-good American makers of drills.

    USED TO BE.

    The entire lot of we "expert" Chik'ns shall have to skip happy hour it turns out to be as dirt-simple as a bad tip-grind, yah?

    Get you at least a small packet of Guhrings. Clear-chip more often. Look to shave costs LATER.


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    I'd likely end up peck drilling about 1/8" per peck with that small of a drill. I get this notion from peck drilling holes manually and that is about as far as you can go without chip packing (the squeak). Any coolant that went down the hole is gone well before you get done a 3/4" peck.

    The chip usually travels up a parabolic drill pretty fast, so it might be worth using one of the G73 high speed drilling cycles, and break the chip 2, 3 or 4 times before making the complete retraction to spin off the chips.

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    Quote Originally Posted by HuFlungDung View Post
    I'd likely end up peck drilling about 1/8" per peck with that small of a drill.
    Aye. One Diameter seldom makes enemies...
    I get this notion from peck drilling holes manually and that is about as far as you can go without chip packing (the squeak). Any coolant that went down the hole is gone well before you get done a 3/4" peck.

    The chip usually travels up a parabolic drill pretty fast, so it might be worth using one of the G73 high speed drilling cycles, and break the chip 2, 3 or 4 times before making the complete retraction to spin off the chips.
    Surely CAN if ground "just so" off the back of it being formed into snakes coiled tight enough to not even touch the flutes or the walls. or at least they appear to not...

    But that's "Old Skewl", prolly no longer even remembered, let alone seen in a CNC world not into snakes nor bird's nests, either one, "flakes" rather...


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    I am lost here, maybe my coffee hasn't kicked in. I thought I read you had a drill run 160 parts, then it broke. Then all of a sudden the drills won't last so you start altering a program that previously made 160 parts on one drill?

    If the above is correct one of 3 things happened. The drill collet was damaged when the drill broke and now has excessive runout. The quality of your aluminum blanks you are running changed, like you were feeding it Kaiser and now you are feeding it Chinese junk 6061. The 3rd option is you aren't using the exact same type drill as before.

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    Quote Originally Posted by Dualkit View Post
    I am lost here, maybe my coffee hasn't kicked in. I thought I read you had a drill run 160 parts, then it broke. Then all of a sudden the drills won't last so you start altering a program that previously made 160 parts on one drill?

    If the above is correct one of 3 things happened. The drill collet was damaged when the drill broke and now has excessive runout. The quality of your aluminum blanks you are running changed, like you were feeding it Kaiser and now you are feeding it Chinese junk 6061. The 3rd option is you aren't using the exact same type drill as before.
    That's why I questioned coolant as a variable that could have easily changed in what sounded like an already proven process. Although, as was said above by someone else, a .750" initial plunge is pretty deep for any coolant to be getting down in the hole especially with that small of a hole. Or it could just be a bad batch of drills like someone also mentioned. Maybe try the same style but from a different company? Seems like those things are more likely to have changed than anything else I can think of.

    Sent from my SM-N960U using Tapatalk
    Edit: I only saw the first paragraph of what I quoted, the second one wasn't there when i was typing. Also good possibilities there.

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    Quote Originally Posted by Dualkit View Post
    I am lost here, maybe my coffee hasn't kicked in. I thought I read you had a drill run 160 parts, then it broke. Then all of a sudden the drills won't last so you start altering a program that previously made 160 parts on one drill?

    If the above is correct one of 3 things happened. The drill collet was damaged when the drill broke and now has excessive runout. The quality of your aluminum blanks you are running changed, like you were feeding it Kaiser and now you are feeding it Chinese junk 6061. The 3rd option is you aren't using the exact same type drill as before.
    160 "parts" @ 8 holes each or 1280 HOLES on one drill, yet.

    That's not exactly a world-record, but still - the amortized cost, holes per drill buys the best drills in this class as are made with not a lot of strain, and is a right happy place to want to get BACK to.

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    Quote Originally Posted by cb750chris View Post
    That's why I questioned coolant as a variable that could have easily changed in what sounded like an already proven process.
    I don't think coolant would become an issue that quickly unless someone just dumped a bunch of straight water in when the thing was low because of coolant getting dumped with the chips instead of evaporation. I do plenty of 25x diameter plus to deep drilling in 6061 in a pretty aggressive nature on a lathe and maintain coolant by sight and smell, rarely breaking drills. Although that is on a lathe. I do agree .750 on a first plunge is a little much, I think I would go .375.
    Last edited by Dualkit; 10-23-2019 at 06:23 AM.


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