Kenna DFT drills & Stainless 316
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  1. #1
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    Default Kenna DFT drills & Stainless 316

    Hi,
    Been drilling with our Kenna DFT Ø47mm (approx. 2 inches diameter) drill into 316 stock today. We just weren't able to break chips, just hefty strings. We're drilling deep - 190 mm. Started off by using recommended values, but tried changing speed/feed as we went along. The problem isn't that it's not cutting, but when it doesn't break chips it packs the flute and causes trouble. Any of you guys used these DFT drills in 316? All tips are appreciated! Trying new and different inserts tomorrow. Machine is a Haas ST30Y which was seeing about 70% spindle loading. RPM was around 1000 and feed approx 0,12mm/rev.img_20200528_172853.jpg

    Edit: We realize that we're going deeper than recommended here, so pecking is last resort if we can't make chips.

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    Your feed is too light. You are at .0046 ipr (translated for us primitives ).
    That size insert drill should be able to handle closer to .01 ipr (0.25 mm).
    Just gradually increase the feed rate until you hear it start to grumble, then back it off a touch.
    A Haas machine can run at well over 100% spindle load, FYI.
    If that still doesn't work you probably have the wrong chipbreaker.

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    Thanks, will give that a try tomorrow! Getting a MS? Insert tomorrow that's supposed to help breaking the chips.

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    Kennametal recommends .004 - .008 IPR on those drills in stainless, so you're in the ballpark. I agree with CS though, a little more feed might do well.

    I've never personally worked with 316 though. Isn't it known for being wildly inconsistent?

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    Not much experience myself with 316 other than asking a lot of companies to make parts out of it for us earlier🙄.
    So far my personal experience is that it breaks chips well when doing outside turning and it's ok during boring. Drilling is a bit tricky so far though, but that big drill is a monster so it will be a bit nerve-racking to bring up the feed some more and try. Sounds like a traincrash when it's ploughing through the 316.

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    Quote Originally Posted by Schjell View Post
    Not much experience myself with 316 other than asking a lot of companies to make parts out of it for us earlier��.
    So far my personal experience is that it breaks chips well when doing outside turning and it's ok during boring. Drilling is a bit tricky so far though, but that big drill is a monster so it will be a bit nerve-racking to bring up the feed some more and try. Sounds like a traincrash when it's ploughing through the 316.
    Your chips are a classic example of feeding a little on the light side. They are "accordion" shaped now, but as soon as you give it enough feed they will come off in 6s & 9s.

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    Quote Originally Posted by ChipSplitter View Post
    That size insert drill should be able to handle closer to .01 ipr (0.25 mm).
    That would be a very heavy feed rate for that drill. Good chance of crunching the centre insert.

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    Quote Originally Posted by gregormarwick View Post
    That would be a very heavy feed rate for that drill. Good chance of crunching the centre insert.
    It's a 47 mm drill.
    I've pushed a 32 mm OSG drill to .008 ipr.
    True, it could be a bit high, but the point is he has room to go up with the feedrate.

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    Quote Originally Posted by ChipSplitter View Post
    It's a 47 mm drill.
    I've pushed a 32 mm OSG drill to .008 ipr.
    True, it could be a bit high, but the point is he has room to go up with the feedrate.
    The chipload capability scales with the size and geometry of the insert, not the size of the drill. The centre insert has effectively zero surface speed, and it's ability to withstand massive pressure determines the maximum feedrate attainable. I have some 50mm insert drills that will handle .25mmpr, and I have some 100mm drills that will absolutely not.

    DFT drills use W shape inserts, which are pretty fragile at the corners. I am prepared to be proven wrong, but I think that .25mmpr is really pushing it for that drill.

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    Quote Originally Posted by ChipSplitter View Post
    It's a 47 mm drill.
    I've pushed a 32 mm OSG drill to .008 ipr.
    True, it could be a bit high, but the point is he has room to go up with the feedrate.
    At some point you have to worry about the "springiness" of the machine. If you get to a load where you start backing the drill up until there's enough force to bounce it forward then you'll have spiking loads on the inserts that could destroy them.

    The other aspect is as above but now add work hardening to the material surface...

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    Okay, get your grains of salt ready.

    I use almost exclusively DFT style Drills. I've crashed them, melted them, broken them and made $1000's with them. It's not a coincidence that I use them as much as I do. I really like them....I use KC7225 for both peripheral and center pockets, and they are the only inserts I use. I usually run alloy steels, 300 and 400 series SS.

    In my experience, the advantage of these Drills is that they are very tough, heavy bodied Drills. As far as MRR goes, I found that they run more productively with higher SFM and lower Feeds. At 1000 RPM you're only at 50 SFM. I would double that and leave the Feed alone (to start). There is a very unique sound that it'll make when it's running best. It'll make the office people poke their heads in to ask if you need an ambulance. It's literally the highest pitched shreek ever.

    R

    Disclaimer; I understand that at a glance my suggestion is against conventional wisdom for SS. Don't go over 200 SFM and don't stop feeding.

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    Quote Originally Posted by litlerob1 View Post
    There is a very unique sound that it'll make when it's running best. It'll make the office people poke their heads in to ask if you need an ambulance. It's literally the highest pitched shreek ever.
    A Sandvik Corodrill 880 is really bad too. I don't know why it's so high pitched but it makes my ears bleed LOL.
    OSG and Ingersoll never have noise issues in my experience, they just make a low grumbling, growling noise.

    YMMV

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    Quote Originally Posted by litlerob1 View Post
    Okay, get your grains of salt ready.

    I use almost exclusively DFT style Drills. I've crashed them, melted them, broken them and made $1000's with them. It's not a coincidence that I use them as much as I do. I really like them....I use KC7225 for both peripheral and center pockets, and they are the only inserts I use. I usually run alloy steels, 300 and 400 series SS.

    In my experience, the advantage of these Drills is that they are very tough, heavy bodied Drills. As far as MRR goes, I found that they run more productively with higher SFM and lower Feeds. At 1000 RPM you're only at 50 SFM. I would double that and leave the Feed alone (to start). There is a very unique sound that it'll make when it's running best. It'll make the office people poke their heads in to ask if you need an ambulance. It's literally the highest pitched shreek ever.

    R

    Disclaimer; I understand that at a glance my suggestion is against conventional wisdom for SS. Don't go over 200 SFM and don't stop feeding.
    I think he's running closer to 500 SFM...

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    Lots of coolant pressure helps. Sounds like you're probably running on the standard pump?
    I find the 145psi of my machine to be about minimum, more would be way gooder.

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    Quote Originally Posted by ChipSplitter View Post
    A Sandvik Corodrill 880 is really bad too. I don't know why it's so high pitched but it makes my ears bleed LOL.
    OSG and Ingersoll never have noise issues in my experience, they just make a low grumbling, growling noise.

    YMMV
    I agree, as much as I like Sandvik, some of their 880's will make you go deaf.
    On that note has anyone used the Kyocera Magic Drills?
    Night and Day difference. They are so quiet and cut like butter. And the inserts are tough as nails.
    And I believe the bodies are a lot less in price than Sandvik, Iscar, Kennametal, etc...

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    Quote Originally Posted by Mtndew View Post
    I agree, as much as I like Sandvik, some of their 880's will make you go deaf.
    On that note has anyone used the Kyocera Magic Drills?
    Night and Day difference. They are so quiet and cut like butter. And the inserts are tough as nails.
    And I believe the bodies are a lot less in price than Sandvik, Iscar, Kennametal, etc...
    I like the performance of the Corodrill 880s but the inserts are wickedly expensive, too.
    I haven't used Kyoceras but that is good to know. Who do you get Kyocera stuff from?
    PF Markey? Shively Bro. ? Iwen?

    I personally like Ingersoll, OSG, and even Korloy for insert drills. Not a fan of the Iscar DR-Twist, though.

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    Quote Originally Posted by ChipSplitter View Post
    I like the performance of the Corodrill 880s but the inserts are wickedly expensive, too.
    I haven't used Kyoceras but that is good to know. Who do you get Kyocera stuff from?
    PF Markey? Shively Bro. ? Iwen?

    I personally like Ingersoll, OSG, and even Korloy for insert drills. Not a fan of the Iscar DR-Twist, though.
    We get them from Carbide Depot. They have really good pricing.
    The site lacks a lot of images, but they do have links to Kyocera's official catalog so you can get the part numbers.
    KYOCERA DRZ MAGIC DRILL

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    Ok, found the sweet spot today in terms of chipbreaking. See attached pics of ideal setup for what we were doing. Tried Robs setup as well with the inserts he uses, but that didn't work for us. img_20200529_142954.jpgimg_20200529_142909.jpgimg_20200529_103306.jpgimg_20200529_102352.jpg

    See my latest post. Wrong feed & speed shown on screen shot.
    Last edited by Schjell; 05-30-2020 at 12:46 AM.

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    Quote Originally Posted by Schjell View Post
    Ok, found the sweet spot today in terms of chipbreaking. See attached pics of ideal setup for what we were doing. Tried Robs setup as well with the inserts he uses, but that didn't work for us. img_20200529_142954.jpgimg_20200529_142909.jpgimg_20200529_103306.jpgimg_20200529_102352.jpg
    Nice!

    So did you use different inserts or the same ones? I converted your feedrate and came up with .0086 ipr (.2236 mm). Is that what you are running?

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    Used the inserts shown on picture. We have the local Kenna sales rep working along with us, so it's all his credit that it worked out so well.


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