Iscar boring bar
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  1. #1
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    Default Iscar boring bar

    Hello all, i am running an 1” iscar bar with a cnmg332 insert. I am having a hell of a time dealing with chatter. I have tried 400 sfm down to 300rpm. I am feeding around .007 to .008 per rev with a doc from .035 to .050 per side. It is being held with a vdi holder. An decent suggestions to stop the chatter?

    Thank you

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    Is the extension more than 3x Dia.?

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    you don't mention what material you are cutting, but increasing the DOC usually helps.

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    The material no, bar stick out is 5” and i am boring back 4.5”.

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    The material is 4340 pre-hard.

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    Quote Originally Posted by FrankieB View Post
    The material no, bar stick out is 5” and i am boring back 4.5”.
    Try running a lower SF,like 150-200. D.O.C. .020-.025
    If your machine has SSV use that also


    Sent from my iPhone using Tapatalk

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    Quote Originally Posted by FrankieB View Post
    The material no, bar stick out is 5” and i am boring back 4.5”.

    Oooo........ you say you have a 1" bar and it's hanging out 5" and you're running 4340 PH? Not an ideal situation by any means.
    Things to try:
    1) Do like someone else above mentioned and vary the RPM constantly. Like uuUUPPP ANd down aND UPpp and .. you get the idea.
    2) Try changing the bar stickout by .25" either in or out. Don't laugh, it can be a lifesaver sometimes. It keep harmonics from building up.
    3) Make the workholding as rigid as possible.
    4) Use a different insert geometry that is more free-cutting, i.e. a finishing insert instead of a rougher.
    5) Try tweaking the DOC.
    6) Make sure your bar is dead on center or a few thou. above.
    7) If all else fails, use a solid carbide or dampened bar. Lots of $$$, but it could save the bacon. If you get a new bar, make sure you get the right insert for the job. I like CCMTs for deep boring, but I know some people don't............


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    CNMG 332...try something with less radius, sharper, positive and uncoated.

    VDI-s suck at times. Hanging bars out in the breeze, held by a couple set screws.

    I used to make snug sleeves for the bars with flats to locate. Bars had to be tapped into the sleeve, then that needed to be tapped into the holder.

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    A lot of great advice already. Steel bars are generally meant for 3xD applications. With different manufacturers tweaking stuff to get 4xD. I would suggest going to a bigger bar with a positive insert like a CCMT if possible. Carbide bars are generally rated for 5xD like you are running. If not possible lower depth and feed like crazy.

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    Quote Originally Posted by Shop Supply Guru View Post
    A lot of great advice already. Steel bars are generally meant for 3xD applications. With different manufacturers tweaking stuff to get 4xD. I would suggest going to a bigger bar with a positive insert like a CCMT if possible. Carbide bars are generally rated for 5xD like you are running. If not possible lower depth and feed like crazy.
    True.
    I have run 4xD but you have to have everything right. I was using a CCMT on that application. IMO, "X"NMG inserts are for medium to roughing. You can get a finishing chipbreaker on them, but they're really overkill for that.

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    If I read this right you might be better off internal grooving and boring.

    If you have a bigger bore in the front of the part maybe you could put the boring bar in a sleeve, giving you the extra dia. you need.

    Good luck.

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    Thanks for all the suggestions i finally got something to work fair. What i really need is to get my hands on a sandvik de-vibe bar.

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    Quote Originally Posted by FrankieB View Post
    Thanks for all the suggestions i finally got something to work fair. What i really need is to get my hands on a sandvik de-vibe bar.
    What did you end up doing?
    Just curious.

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    Slowing everything way down. Rpm was around 135-140 and feed was 0.0054. The
    finish was junk but i hit it with paper and got it good enough.


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