Flexbar flycutter advice
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  1. #1
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    Default Flexbar flycutter advice

    Has anyone used a Flexbar brand flycutter? Any recommendations for speeds and feeds? It has 2 tool bits oriented vertically. Will be machining aluminum, just cleanup facing, .01" or so.

    Flexbar 6" Simul-Cut Fly Cutter Tool - 19006 - Penn Tool Co., Inc

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    Yes, I have some data. One of our senior machinists used to use one on a Bridgeport to deck off large plates because he could do it in one pass. One day he went to clamp the quill lock and his hand slipped and went straight into the cutter. We found one of his four fingers in rafters about twenty feet away. He was spinning the cutter at 2400 RPM, you may want to go slower or faster depending on the hardness of your fingers.

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    Quote Originally Posted by G00 Proto View Post
    Yes, I have some data. One of our senior machinists used to use one on a Bridgeport to deck off large plates because he could do it in one pass. One day he went to clamp the quill lock and his hand slipped and went straight into the cutter. We found one of his four fingers in rafters about twenty feet away. He was spinning the cutter at 2400 RPM, you may want to go slower or faster depending on the hardness of your fingers.
    oh my gawd

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    fly cutters work extremely well, I have not used this model, but it does not look beefy enough.
    you will need a roughing and finishing pass, I not sure I like these double cutters, I like to measure my parts
    for the finishing pass. I use a drop indicator to get an exact DOC for final size. old school.
    I seen accidents over the years. and it's not trivial. that's why the new VMC have sliding doors to activate (start)
    the controls, I like the new stle VMC and CNC lathes for that reason, safety, safety, safety, I started out on a bridge port style mill, and an old turret lathe,
    and it was common back then for old timers to have missing fingers. engine lathes are the worst, because
    always getting near the chuck spinning at high RPM. but the old sheet metal brakes were the worst.
    I seen operators loose they entire hands due to lack of or altered safety devices.

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    Quote Originally Posted by G00 Proto View Post
    Yes, I have some data. One of our senior machinists used to use one on a Bridgeport to deck off large plates because he could do it in one pass. One day he went to clamp the quill lock and his hand slipped and went straight into the cutter. We found one of his four fingers in rafters about twenty feet away. He was spinning the cutter at 2400 RPM, you may want to go slower or faster depending on the hardness of your fingers.
    This will be in an enclosed CNC. I know there was a video out there where a cylinder facind head (?) went through an entire building. I don't think the flexbar has nearly enough mass to do that, but I know it could cause some serious damage if the rpm gets up there. Unless someone have some definitive numbers we will likely just start at 2-300 rpm and work our way up to our comfort level.

    And yuck, that's gotta suck to lose fingers.

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    Quote Originally Posted by G00 Proto View Post
    ...We found one of his four fingers in rafters about twenty feet away....
    So of the 4 he lost only 1 was found in the rafters? Or he only had 4 to start and is now down to 3?

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    This shit's chess, it aint checkers!

    I'm far from a safety oriented individual but tools like that make me slow down and think twice, maybe even thrice. But I don't doubt it works great when used correctly. I'd be interested so see the results.

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    This or homemade versions work fine for me.
    Advantage one over a normal single flycutter is balance.
    I set one tooth .001 proud or high to control the finish.
    Bob

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    Quote Originally Posted by G00 Proto View Post
    Yes, I have some data. One of our senior machinists used to use one on a Bridgeport to deck off large plates because he could do it in one pass. One day he went to clamp the quill lock and his hand slipped and went straight into the cutter. We found one of his four fingers in rafters about twenty feet away. He was spinning the cutter at 2400 RPM, you may want to go slower or faster depending on the hardness of your fingers.
    And this is why I don't like fly cutters. Next to a lathe probably the most dangerous thing you can use in a machine shop. The old guy at work swears by them and refuses to use shell mills. I am the exact opposite.

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    Quote Originally Posted by Hardplates View Post
    This shit's chess, it aint checkers!

    I'm far from a safety oriented individual but tools like that make me slow down and think twice, maybe even thrice. But I don't doubt it works great when used correctly. I'd be interested so see the results.
    I'm not happy about having to use one, but alot of the parts we make have high cosmetic requirements and the bossman don't like to see "lines" where a tool has taken multiple passes (I know, I know, but he signs my paycheck).


    I don't think I am going to need it right away now. We were having finish problems, but we seem to have it dialed in... for now. I'll report back if we end up using it for something else.

    What's scary is they make a 10" version, still with a 3/4" shank!

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    I gotta admit, the scenario of one's hand slipping off the little spindle lock lever on manual BP mills has been making me nervous for decades, so I either stop the spindle or use extra-extra caution when actuating it. But inside a VMC I'd be OK with that style flycutter, used wisely.

    But I'm not sure I buy the "rough-finish" aspect, as you're dealing with vibration/flex of each limb as it goes over the workpiece, and it could take some tuning of speeds to damp down resonance that might drive the cutter into the work in non-optimal waves.

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    Quote Originally Posted by Cole2534 View Post
    So of the 4 he lost only 1 was found in the rafters? Or he only had 4 to start and is now down to 3?
    I believe he started with shift a full compliment of 10 and clocked out with 7.5 fingers. Final inventory from right to left: 0%, 25%, 50%, 75%, 100%. This was not his first machining related hospitalization, nor I doubt his last... kinda funny since he was the only person in 25 years that ever implied that I was a slow machinist. I suppose pausing before doing something stupid is a form of malingering

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    Quote Originally Posted by Mike1974 View Post
    I'm not happy about having to use one, but alot of the parts we make have high cosmetic requirements and the bossman don't like to see "lines" where a tool has taken multiple passes (I know, I know, but he signs my paycheck).


    I don't think I am going to need it right away now. We were having finish problems, but we seem to have it dialed in... for now. I'll report back if we end up using it for something else.

    What's scary is they make a 10" version, still with a 3/4" shank!

    Try this: https://www.iscar.com/eCatalog/item....FSTYP=I&isoD=1

    Not cheap but they do an awesome job. And you could do 150 IPM in aluminum.

    This explains how they work: https://www.iscar.com/eCatalog/MoreI...app=61&isoD=-1

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    Are you looking for material removal or finish? I have been using the Cogsdill face burnishing tool for about a year now and it is absolutely awesome on finishes.
    Last edited by g-coder05; 08-04-2020 at 06:15 PM. Reason: My punctuation is poor...

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    I had a similar need for a 6” dia cutter for use in our VMC. I went the shop built route.

    We have an aluminum disk 7” round and 1.25” thick mounted securely to a Maritool face mill holder. The aluminum disk has a 3/8” square hole broached in it for a tool bit.

    I have been using a brazed on carbide tool that is meant for boring. McMaster Carr sells them. It’s the exact geometry I wanted in a fly cutter, positive rake and skewed.

    I’ve also seen the video of the square fly cutter blowing through the shop, scary! The round cutter reminds me of running a lathe. Great finishes and flat, I’d recommend this as a safe and affordable solution.

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    If'n yer going for finish, you might as well go diamond. Either PCD or natural. Natural gives an even better finish (no cobalt to stick to), but more spendy.

    As long as nobody trashes it or you don't hit an inclusion, natural diamond will give you near-permanent final finish and accuracy.

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    Quote Originally Posted by g-coder05 View Post
    Are you looking for material removal or finish? I have been using the Cogsdill face burnishing tool for about a year now and it is absolutely awesome on finishes.
    Surface finish. We have facemills, but boss don't like seeing lines if the part is wider than the cutter and have to make stepover(s). I think it is a bit overkill, but again, I have seen some of the pricing so I sort of understand the requirements, although I doubt the end user is as concerned as we are. I would prefer a brushed matte anodize as it 'hides' alot more imperfections.

    As to the flexbar, their recommendation is (extrapolated) about 500 rpm and 10ipm in aluminum for the 6" size.

    edit: Looking into those now, thanks for the heads up. Do you know if you use a smaller tool and make multiple passes in X/Y if it leaves any marks in between?

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    edit: Looking into those now, thanks for the heads up. Do you know if you use a smaller tool and make multiple passes in X/Y if it leaves any marks in between?
    We run 3" and it seems to be machine specific. If the tram is off then it does have a touch of a step but not as bad since the inserts are spring loaded. One thing I have noticed is if the part will go for a coating afterwards it doesn’t like to absorb. The burnish just kills the porosity.

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