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IndustryArena Forum > MetalWorking > MetalWork Discussion > Are these numbers ok for a36?
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  1. #1
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    Are these numbers ok for a36?

    I've been looking for a suitable brake rotor for my mill turn project but there's just nothing exactly how i want it so I ordered a blanchard ground 8x8 3/16 thick a36 plate. Slowest my spindke can go is 7200rpm, but I think I'll be ok. I'm going to slot cut with a 1/8 carbide emdmill. At 7200rpm I'll be at 235 sfm. Will this be ok? Figure I'll just do shallow passes. What about coolant? I work with mostly aluminum so I'm set up with mist coolant using koolmist. Should I use it? I obviously won't be able to drill the a36 at 7200rpm so I'll just interpolate the bolt holes as well.
    Will I be ok at 235sfm? If that's too hot, I can get a smaller endmill. I'm only cutting 3/16 deep so even a 2mm endmill would probably be fine and get it down to 150sfm but I'd rather use what I have if it'll be ok.

  2. #2
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    Re: Are these numbers ok for a36?

    This may change your (and my) thinking on surface speeds. But it may require a really rigid machine. I think the key is the tool path and of course the tool. So 7200 RPM, proper carbide endmill, proper engagement and tool path should work.

    https://youtu.be/6dFL3QIZwz8
    Jim Dawson
    Sandy, Oregon, USA

  3. #3
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    Quote Originally Posted by Jim Dawson View Post
    This may change your (and my) thinking on surface speeds. But it may require a really rigid machine. I think the key is the tool path and of course the tool. So 7200 RPM, proper carbide endmill, proper engagement and tool path should work.

    https://youtu.be/6dFL3QIZwz8
    Ha! 19k rpm with a 3/8 tool in steel, 1860 sfm. That's insane! Yeah I'm sure I'll probably be ok with my 1/8 at 7200.

  4. #4
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    Re: Are these numbers ok for a36?

    Quote Originally Posted by QuinnSjoblom View Post
    I've been looking for a suitable brake rotor for my mill turn project but there's just nothing exactly how i want it so I ordered a blanchard ground 8x8 3/16 thick a36 plate. Slowest my spindke can go is 7200rpm, but I think I'll be ok. I'm going to slot cut with a 1/8 carbide emdmill. At 7200rpm I'll be at 235 sfm. Will this be ok? Figure I'll just do shallow passes. What about coolant? I work with mostly aluminum so I'm set up with mist coolant using koolmist. Should I use it? I obviously won't be able to drill the a36 at 7200rpm so I'll just interpolate the bolt holes as well.
    Will I be ok at 235sfm? If that's too hot, I can get a smaller endmill. I'm only cutting 3/16 deep so even a 2mm endmill would probably be fine and get it down to 150sfm but I'd rather use what I have if it'll be ok.
    Drop the minimum speed Parameter in the VFD down to 100 this will get you at 6000 RPM
    Mactec54

  5. #5
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    Re: Are these numbers ok for a36?

    Quote Originally Posted by Jim Dawson View Post
    This may change your (and my) thinking on surface speeds. But it may require a really rigid machine. I think the key is the tool path and of course the tool. So 7200 RPM, proper carbide endmill, proper engagement and tool path should work.
    On a $250 thousand Plus machine anything like this is possible how could you make a comparison to a $150 to $250 dollar spindle that is not designed to cut steel
    Mactec54

  6. #6
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    Re: Are these numbers ok for a36?

    Quote Originally Posted by mactec54 View Post
    On a $250 thousand Plus machine anything like this is possible how could you make a comparison to a $150 to $250 dollar spindle that is not designed to cut steel
    You mean that you can't do that on just any Chinese table top router, huh, I'll be darned, who would of guessed? :stickpoke

    I have been chatting with QuinnSjoblom on various subjects on this forum long enough to know that he would understand the point of my post and get the joke. And I could tell from his response that he got it, unlike others. HeII, my Haas wouldn't even do that, that DMU 50 in the video has a 50 HP spindle and weighs ~12,000 lbs.
    Jim Dawson
    Sandy, Oregon, USA

  7. #7
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    Re: Are these numbers ok for a36?

    But it may require a really rigid machine
    hello jim, yes, there are a few things

    on a more rigid machine, you can go faster, but is good to know how to scale the process to fit a less rigid machine

    otherwise, is dangerous, even on a rigid machine

    on okuma ( lathe, mills ) i use load comparative method, checking load dinamycally to avoid sudden peaks, that may lead in time to signifiant wear

    also, diff is cheked, to avoid increasing the backlash

    is easy to say, but harder to implement; not impossible

    in short, it is required to monitorize the process, observe and adjust accordingly, like mapping the feedrates, and others

    also, there are forces that can not be monitorized, but may distroy the machine, especially when going such fast

    there are persons that simply avoid such specs, because, even if they work ok, they can not predict or react fast in case of a sudden failure, with not-so-nice consequences / kindly
    Ladyhawke - My Delirium, https://www.youtube.com/watch?v=X_bFO1SNRZg

  8. #8
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    Quote Originally Posted by Jim Dawson View Post
    You mean that you can't do that on just any Chinese table top router, huh, I'll be darned, who would of guessed? :stickpoke

    I have been chatting with QuinnSjoblom on various subjects on this forum long enough to know that he would understand the point of my post and get the joke. And I could tell from his response that he got it, unlike others. HeII, my Hass wouldn't even do that, that DMU 50 has a 50 HP spindle and weighs ~12,000 lbs.
    Haha! Nope, I totally took that as "you should crank it up to 19k and just let it rip" lol.

    Totally understood Jim's post. obviously I can't do that with my machine, but at the same time I think it shows what modern carbide tooling can do these days and standards for specific sfm in specific material is definitely not set in stone.

  9. #9
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    Re: Are these numbers ok for a36?

    Quote Originally Posted by Jim Dawson View Post
    You mean that you can't do that on just any Chinese table top router, huh, I'll be darned, who would of guessed? :stickpoke

    I have been chatting with QuinnSjoblom on various subjects on this forum long enough to know that he would understand the point of my post and get the joke. And I could tell from his response that he got it, unlike others. HeII, my Hass wouldn't even do that, that DMU 50 has a 50 HP spindle and weighs ~12,000 lbs.
    You where just fantasizing we got it, but some would still think it is possible by what you posted (nuts)

    You would be surprised this same thing has been done on Haas machine before and by Zone members
    Mactec54

  10. #10
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    Re: Are these numbers ok for a36?

    So here's what I'm curious about in that video, limits are being pushed without coolant. Is this common practice for steel? I generally don't mill steel so I just don't know. I would think the main limitation when pushing limits is heat, so would think coolant should allow the limits to be pushed further, or does it just create more problems like thermal shock? I imagine the biggest heat remover is the chips leaving the cut and taking the heat with.

  11. #11
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    Re: Are these numbers ok for a36?

    Great question. And I don't know. I have always use coolant (and much slower surface speeds) but ''that's the way we have always done it''. You are correct that most of the heat (should) leaves with the chips. But in the video, with the exception of the spiral plunge cuts, the chips don't even seem to change color. I need to kinda re-think some of the stuff that I ''know''.
    Jim Dawson
    Sandy, Oregon, USA

  12. #12
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    Quote Originally Posted by Jim Dawson View Post
    Great question. And I don't know. I have always use coolant (and much slower surface speeds) but ''that's the way we have always done it''. You are correct that most of the heat (should) leaves with the chips. But in the video, with the exception of the spiral plunge cuts, the chips don't even seem to change color. I need to kinda re-think some of the stuff that I ''know''.
    I noticed that too. Would have expected blue chips running that hard.

  13. #13
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    Re: Are these numbers ok for a36?

    hi quin, i noticed that you + jim = love

    i don't have jim's patience

    about 'modern' carbide, i set up long term setups. and differences between low quality carbide and high quality are like 1-2 hours versus 4 shifts, on same cuting specs

    depends, but less tool changes are better, and also less offset corections is better / kindly
    Ladyhawke - My Delirium, https://www.youtube.com/watch?v=X_bFO1SNRZg

  14. #14
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    Re: Are these numbers ok for a36?

    so would think coolant should allow the limits to be pushed further
    some tools, especially when milling, may break because of thermal fluctuation : for example, if the tool is cutting between 0*-45* and coolant is on 0-45, then, things are 'stable' as long as the coolant flow is stable

    if tool is changing cutting side, to 90-135*, but there is no coolant in that area, then a termic shok apears when leaving / entering the coolant zone

    solution :
    ... through tool coolant
    ... coolant flood ( using showers, etc )

    some tools are sensitive to termic shock, so, is better to go 'dry', as long as coolant flow is not uniform arround the tool; from this perspective, some tools are designed to go 'dry'

    on some setups, there is a reaction between the colant and the material, near the cuting edge, which is not benefic for the tool; about this last thing, i did not experimented it, i was only told / kindly
    Ladyhawke - My Delirium, https://www.youtube.com/watch?v=X_bFO1SNRZg

  15. #15
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    Re: Are these numbers ok for a36?

    Quote Originally Posted by QuinnSjoblom View Post
    I noticed that too. Would have expected blue chips running that hard.
    Don't worry the chips after they leave the cutting area they change color from a straw dark straw to a blue depends on the cut, they may have the air going through the spindle as well, in your case your mister would do a good job, with the air to move the chips will help a lot
    Mactec54

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