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Thread: Fly Cutter Bits

  1. #1

    Default Fly Cutter Bits

    I just got a cheap 3 piece fly cutter set from Grizzly. It came with unsharpened bits. I have never done anything like sharpen fly cutter bits.
    Where can I find some drawings or pictures of sharpened bits?
    Thanks
    Jack

  2. #2
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    most guys grab a knife tool and let er rip - it'll sort of work, but the geometry is imo wrong.

    here's some links giving my ideas on the subject

    http://bbs.homeshopmachinist.net/showthread.php?t=31810

    Here is a thread with some pics I did to try and illustrate the point for fly cutters

    http://www.cnczone.com/forums/showthread.php?t=28295

    and here is a lathe facing tool, my fly cutting bits are identical except the clearance is ground on the other (for normal forward rotation, as shown will work if run in reverse) .

    http://i20.photobucket.com/albums/b2...facingtool.jpg

    you are also better with hss than carbide as you will get a more acute angle....but i use carbide as well when the diameters get larger (and hence need a faster cutting tool)
    Last edited by Mcgyver; 01-22-2010 at 09:35 PM.

  3. #3
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    Here ya go.

    It's only ink and paper

  4. #4
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    If in doubt look up sahaper cutters as that what the cutter is doing except its going round instead of back and forth.
    Also needs a lota of mass behind the cutting face.
    Peter
    I have tools I don't know how to use!!

  5. #5
    Join Date
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    Collierville, TN
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    http://madmodder.net/index.php?topic=850.0

    4th post down shows one way. I tried it and it worked great for me!
    Milton

    "Accuracy is the sum total of your compensating mistakes."

    "The thing I hate about an argument is that it always interrupts a discussion." G. K. Chesterton

  6. #6
    Join Date
    Jan 2009
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    I recently built one and I use a left handed carbide cutter...no sharpening needed.

  7. #7
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    Note: brazed carbide is not required, or recommended unless you have a diamond wheel to reshape and resharpen as needed. (They tend to come 'dull' and need a good sharpening outta the box, letting them dull further results in chiping them.. and then you REALLY need a diamond wheel to grind away the chiped part.. diamond laps don't cut it, iv tryed)

    Carbide inserts are good without any tooling to sharpen them of course.

  8. #8
    Join Date
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    They are sharpened much like lathe or scraper bits. You need the basic rake and clearance angles. You need to observe how they are mounted in the cutters and adjust the angles to compensate for that position relative to the work piece and the motion of the cutter.

    If they are like the three piece fly cutter sets I have seen, the rake angle will probably be relative to the "top" edge of the tool bit (the edge that is radial when mounted), just as it would be in a lathe when mounted horizontally.
    This rake angle is usually positive, but can be zero (no grinding required) or negative depending on what and how you are cutting. I would start with about 5 - 8 degrees positive rake: that will work best for all around cutting.

    These cutters usually have the tool held at a downward angle to allow both surface finishing and cutting to a step. For the clearance angles, this mounting angle must be taken into account. Other geometries are possible, but generally the two clearance angles (bottom and side) are generated to allow the tool tip to cut to a square inside corner. I have shown it this way here:



    The main place where the geometry differs from a lathe tool is at the outside or horizontal clearance angle. Here, you will probably have to add a second grind to produce a secondary clearance angle that is considerable greater than the primary to prevent the tool from rubbing. This is because it is cutting on the INSIDE of an arc: this is illustrated in the magnified view.
    Paul A.

    Make it fit.
    You can't win and there is a penalty for trying!

  9. #9
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    Quote Originally Posted by Black_Moons
    Note: brazed carbide is not required, or recommended unless you have a diamond wheel to reshape and resharpen as needed. (They tend to come 'dull' and need a good sharpening outta the box, letting them dull further results in chiping them.. and then you REALLY need a diamond wheel to grind away the chiped part.. diamond laps don't cut it, iv tryed)

    Carbide inserts are good without any tooling to sharpen them of course.
    If you use the "EZE-LAP" or the competitor to them, you should be able to rather quickly relieve brazed carbide cutters for fly cutting, or take out minor chipping . I have done it quite a bit.

    You need to have the coarse AND fine ones.....

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