Fly Cutter Rough Surface Finish on Carbon Steel - Page 2
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  1. #21
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    One shop I worked in got the job of facing both sides of some cast aluminium cover plates. They were about 3ft by 2ft by about 1.25" thick. Flat on one side and with several bosses on the other side. There were about 50 in the batch.

    After trying several milling cutters without great success the guy doing the job opted to fly cut them. That method turned out ok but in spite of trying to box the job in we were finding the chips up to 50 feet away for weeks afterwards !

    Regards Tyrone.

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    Quote Originally Posted by Spruewell View Post
    That definitely appears to be cast Iron, which will not require lubrication. Your tool is sticking out way too far, reduce the cutting diameter as much as you can. It is in the fly-cutter head backwards (you will also need the reverse of that tool holder style). That fly cutter is meant to turn the other direction. Cutting edge of insert should be about centerline of the tool. Lower your RPM to between 100-200 rpm and you should be able to get a decent finish at about 2-4 i.p.m. With anywhere from .01 to .04 depth of cut.
    I picked up this part in a scrap yard and it appeared to be an old tooling fixture used in machining so had assumed it to be carbon steel, many have suggested it's cast iron so I imagine it is that. I will try reducing my cutting diameter but as for the fly-cutter head spinning backwards can you discuss further why the direction of it spinning would make a difference in cut assuming the insert's cutting edge is the leading edge and everything else is held constant and correct? The cutting is on the center of the line, the picture may look like it's offset. Also, many have suggested I have an R8 shank but the shank is NMTB40. I will try your suggestions, and those of others, and let you all know how it goes. I very much appreciate your reply and those of others!

    Cody
    Last edited by cfoxx911; 02-22-2018 at 09:15 PM. Reason: Correct some wording

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    Quote Originally Posted by SilveradoHauler View Post
    Fly cutter is way too small. Too much overhang with the tool. Wrong tool bit geometry. Feed to fast. Spindle RPM too fast.

    If you have much of this to do, buy a big fly cutter. Below, 3 inch A36 flat bar, the fly cutter is 3" in diameter. With a little tool projection the cut is made in one pass. I am using 3/8" HSS tool bits in the fly cutter. Note the cutting oil.

    Attachment 2212972+

    For my operation in the photo:

    4 times the cutting speed divided by the diameter:

    A36 steel cutting speed is 100

    diameter of the tool about 3 1/2 inches say 4 for simplified calculations

    4 times 100 divide by 4 gives me about 100 RPM

    In addition to the 8 speeds in my mill I have a 3 hp DC motor on it with variable speed drive controller. I set the gearing/belts to approximate rpm and fine tune with the speed controller

    So I am saying your 1300 rpm is way too high.
    img_0725.jpgimg_0724.jpgimg_0723.jpg

    SilveradoHauler, I appreciate your advice. I infact do have a larger, more precise facing tool. I chose to try the fly cutter to compare finished surfaces to see if the fly cutter does a decent job but I wanted to make sure I was covering all my bases when it came to fly cutting to make sure I was doing it right. I was took quick to assume the part was carbon steel because many have suggested it's cast iron so it is probably that. My mill has a 5hp motor 3 phase with variable speed drive so I will look into fine tuning that as you suggest. Thanks for the help.

    Cody

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    Quote Originally Posted by BobM3 View Post
    Hard to see but it looks like the cutting corner of your tool is quite worn. There's also a big exit burr which would indicate a dull tool.
    As I said in my post, the insert is brand new and has no signs of wear when I compare it to a new one. Thanks for your reply.

    Cody
    Last edited by cfoxx911; 02-22-2018 at 08:47 PM. Reason: Needed to add extra content

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    That's actually fairly humorous, running the tool in backwards rotation and expecting it to cut. You have to reverse the spindle motor when changing from high to low range....that's the way these animals are. Look for the reversing switch.

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    Quote Originally Posted by HuFlungDung View Post
    That's actually fairly humorous, running the tool in backwards rotation and expecting it to cut. You have to reverse the spindle motor when changing from high to low range....that's the way these animals are. Look for the reversing switch.
    The tool is spinning in the direction of the insert's cutting edge so how is that the wrong direction? Also, I had missed the obvious, putting it in reverse when adjusting the from high/low rpm range. Thanks for your reply.

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    Big advantage of a fly cutter is they can sweep a wide part..but feed should be perhaps .015 per revolution ..and the Rpm should not be so high...even at .015 per you will see an arc of the radius in the cut.
    Just for fun draw your insert a 10 x scale..then draw .015 length at 10 x scale...you can see the scalp that would be made on the part.

    The one sweep looks cool and it looks and seems flat...but often it is not as flat as say a 3/4 end mill making perhaps 5 passes. Even though the 5 passes may look not as flat a indicator sweep will tell

    To be flat the lead cut and the follow cut would cross hatch on the part, showing the machine dead tram true.

    Perhaps a good way to whack a pert down to perhaps +.020 as a rough in or a part not needing a good surface finish..If the one pass beat the few passes and done so not damaging the machine.
    Last edited by michiganbuck; 02-23-2018 at 09:28 AM.

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    All of the above points are good. One more thing you might want to double check is the security of your workholding as shown in your first photograph. Are the surfaces of your workpiece flat enough, and square enough, to obviate rocking (the chatter issue) as your cutter hammers on its edge? What I'm looking at are the junction lines where the vertical surface contacts the near jaw of the vise, and where the bottom surface contacts the near stack of parallels. If your clamping is good, I might just be seeing a lighting artifact.

    -Marty-

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    Good post grinding a too bit you tube...
    Not to rob the thread so don't discuss this here but note how you have to push a hard steel part(tool bit) into a wheel to even make a few sparks.

    That is how much pressure is needed on a surface grinder , or any grinder to take stock from a hard part..A lot of pressure..

    For a fly cutter or any cutter I like to consider the circle radius the OD swing makes, then have a plus 5* minimum to perhaps 18 maximum (for aluminum)under the cutting edge clearance inside that circle.

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    If you are hell bent on seeing how a fly cutter does...take all but 1 insert out of your facing mill and run it...I've done it before and it works quite well lol.

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    Quote Originally Posted by JRIowa View Post
    This is a first for me. I've never seen anybody use a turning tool in a fly cutter.
    JR
    Then you are not familiar with wood working. A setup like that is used for boring a hole in a piece of wood on a drill press.

    It's a rather ridiculous arrangement in this case for cutting metal. Hoping to get a smooth finish at any RPM is a pipe dream. It's rather stupid and accident prone as well.

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    Quote Originally Posted by rons View Post
    Then you are not familiar with wood working. A setup like that is used for boring a hole in a piece of wood on a drill press.

    It's a rather ridiculous arrangement in this case for cutting metal. Hoping to get a smooth finish at any RPM is a pipe dream. It's rather stupid and accident prone as well.
    I'm curious on why this is ridiculous and stupid as you suggested, can you provide technical reasoning and your personal experience behind this? I've found so many examples of using fly cutters successfully in face milling and boring operations. What I find so appealing about them are the extremely low cost in inserts and simplicity of them, I'd just like to nail down the surface finishing aspect and then I'd be golden.

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    Some times to get the speed of an end mills(few passes)the fly cutter may need to turn at higher RPM. This high RPM can be tough on machine balance and hard whacking is not very good for bearings..
    looking for the sweep finish the fly is good with being run at fair, safe speeds. One can grind a fly with a .010 (or so) flat and get a good finish.

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    Quote Originally Posted by cfoxx911 View Post
    The tool is spinning in the direction of the insert's cutting edge so how is that the wrong direction? Also, I had missed the obvious, putting it in reverse when adjusting the from high/low rpm range. Thanks for your reply.
    From what I can tell in the pictures your tool is facing the wrong way, for the way the spindle normally rotates.

    I can't claim to be an expert on fly cutting as I have only done it a few times, but the attached sketch may shed some light on what is going on. The view in the center at the bottom is the way that tool would be positioned in a lathe, with the cutting force coming down on the flat part of the tool (of course the drawing represents a tool with neutral rake but that's just for reference). The view to the left shows the cutting force on your tool as it is, with the spindle running in its normal direction, clockwise.

    The view on the right is two possible solutions that may give you more success: run the tool as it is, with the spindle rotating the opposite direction that is normally turns, counterclockwise, or change your tool holder so you can keep the spindle rotating clockwise, and still have the cutting forces hitting your tool in the correct direction.

    As others have said, your tool is hanging out from the holder rather far. Even with a properly positioned tool/rotating spindle you may still get some chatter, or may have trouble machining to a tight tolerance.

    20180224_202621.jpg

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    I prefer a good quality toolsteel for flycutting not cheap stuff and then you grind it by hand loads of examples on youtube how to grind a flycutter then try a cut might need a bit more clearance here and there its trail and error.You want it sticking out as little as possible speed start as suggested at 100revs and increase gradually if needed it looks like C/Iron remember everything behind the cutting edge is clearance another reason why I prefer a good quality toolsteel you can tweak the clearance untill its cutting well a small radius or flat on leading edge is recommended its trail and error untill its cutting well.I was lucky on my first one found an ancient tool that had strange clearance on obviously not a lathe tool someone had tweaked it cuts any material leaves a mirror finish cuts smooth and takes deep cuts in its stride so over the years it gets locked away last job was on large fabrication and they asked if I had ground them its all about the tool and the grinding-In your case a cast iron cutting tip would help
    Last edited by onecut; 02-25-2018 at 03:28 PM.

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    Quote Originally Posted by cfoxx911 View Post
    I'm curious on why this is ridiculous and stupid as you suggested, can you provide technical reasoning and your personal experience behind this? I've found so many examples of using fly cutters successfully in face milling and boring operations. What I find so appealing about them are the extremely low cost in inserts and simplicity of them, I'd just like to nail down the surface finishing aspect and then I'd be golden.
    If you cannot tell from the pictures and the over-hang then keep doing it. Be sure to keep a phone in the shop and practice dialing 911 emergency with your nose. That's the safety aspect.

    The finish shown looks like the flat of a file. A cheap inexpensive approach like that does a low quality job for finishing. For boring I have used the method for very large diameter holes. But I use it for a very last resort.

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    Quote Originally Posted by Terry Keeley View Post
    Can someone explain to me why this is different than a lathe tool? Grind top rake according to material, grind appropriate clearances, no difference.

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    I do see now that the top of his cutting tool isn't on the centerline of the holder. I make my flycutters with the holder slot offset so I can use my lathe tools.


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