chatter and vibration machining
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  1. #1
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    Unhappy chatter and vibration machining

    I am machining a 34" diameter of 6061 alum on a 24" faceplate with 5.25" over hang all around the outside. It is .75" thick and bolted to the faceplate in 4 places. I am grooving the outer 4.5" (all over hang). Its not bad when I get close to the faceplate, but lots of chatter and vibration when I get towards the OD and as it gets thinner. I'm having trouble because its not fully supported I believe. what can i do to get rid of the chatter and vibration?

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    slow it down?

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    smaller radius on cutter
    slow speed and feed
    is tool only out of holder as much as needed
    heavy DOC sometimes

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    Loob ?

    Tool nose radius ?

    Maybe try a Die grinder mounted in toolpost ?

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    A positive rake tool will reduce you cutting pressure. Or try a narrower tool.

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    Gooseneck tool holder?
    More on Spring tools

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    Quote Originally Posted by Conrad Hoffman View Post
    Gooseneck tool holder?
    More on Spring tools
    Interesting, never seen one before. Seems to me it would increase chatter as it could 'give' then dig in, then give, then spring/dig in etc..?

  9. #8
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    No, the clever thing is how they arrange the flex point. Normally, a tool digs in a bit and moves towards the work, digging in more. Imagine the tool post bending in a bit towards the work under load. Then material gets removed, it releases and you have chatter. With the flex point in the right place, and being a bit more compliant than the compound/tool holder, the tool will tend to move away when it tries to dig in, thus, little or no chatter. Supposedly very good for threading and parting off, though I've never tried one. I actually have the loop from a commercial one, but no holder to mount it. Need to make something to try it.

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    Slow it down.
    Smaller radius on the tool.
    Light d.o.c.
    higher feed rate.
    Watch the tool height closely.
    Try WD40 as a cutting oil. (Cheap, works great on Al. Leaves a great finish to boot.)

  11. #10
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    Does your part ring if you tap it on the overhang? If so might want to try to damp it in some way to avoid resonance. I've used something "gooey" stuck on the back of the overhang with double face tape.

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    Quote Originally Posted by brshannon1 View Post
    I am machining a 34" diameter of 6061 alum on a 24" faceplate with 5.25" over hang all around the outside. It is .75" thick and bolted to the faceplate in 4 places. I am grooving the outer 4.5" (all over hang). Its not bad when I get close to the faceplate, but lots of chatter and vibration when I get towards the OD and as it gets thinner. I'm having trouble because its not fully supported I believe. what can i do to get rid of the chatter and vibration?
    .
    .
    use a roughing and finish pass. say groove .300" wide use a .250 or .188 grooving tool and make side by side passes (short tool stickout) leaving .010 on sides and bottom of groove. remove bulk of material
    .
    then when taking finish pass the cutting forces are less.

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    Run the spindle in reverse and turn the tool upside down.

    Ed.

  14. #13
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    its like machining anything. you take it all in one pass you going to get more vibration and a rougher finish that if you take a separate roughing and finish passes
    .
    most who machine a keyway for example find its better to rough it out the majority of stock then just take light finish passes for a tighter tolerance and better finish. groove on lathe is same
    .
    on a lathe if turning 10" od down to 9.0000 you going to take it all in one pass ? or rough it out and then take a light finish pass


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