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Pt3: An Endmill Flute Grinding Fixture (EMFGF) for the Cheezy Surface Grinder (CSG)

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  • Pt3: An Endmill Flute Grinding Fixture (EMFGF) for the Cheezy Surface Grinder (CSG)

    Pt 3: the end. Ay Caramba!

    The finger axis is also tipped back X degrees to better follow the endmill helix -- important for clearance into the narrow flute gullet on smaller diameter endmills, and to allow the guide to run as far as possible into the flute washout @ the shank. Tried a few finger tips: 1) a stainless steel screw with relieved tip -- ok, but wears. 2) a couple of ball bearing tips -- ok on larger endmills where the gullet is taller than the bearing. 3) a stud with replaceable flat washer as the tip -- necessary for small endmills; easily replaced and simplest all around. A thin tip is necessary to contact the gullet and not the flute edge so that you are not cyclically altering your guide reference. A finger-locking jam nut is positioned to make the weakest 10-32 screw portion as short (stiff) as practical.

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    Rest arm versions 2 and 3 are shown. V2 has fixed 7 deg cant, 20 deg tipback. V3 has adjustable height, cant and tipback - better for high helix angle endmills, and almost essential to account for a wide variety of flute widths and depths . But either OK.

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    The CSG lacks table locks; a longitudinal lock was cobbled onto the right end. On the left end, made a telescoping rod crossfeed stop so that would not bozo the wheel, endmill shank or the finger rest while not paying attention. It is also a visual aid that your intended dial zero is coming up soon (sans DRO).

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    The setup accommodates up to a 1.5" endmill as long as the shank is within the ~0.8" ER32 capacity. Have sharpened endmills as small as 3/16", but by that size, you gotta start asking wtfamidoing.

    Out of order picture for part 2:

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    Notes:

    a) A Spindexer is a poor alternative. Lot of drag, and considerable deflection. And way too tall to fit under the CSG spindle housing. If you rotate everything 180 for clearance, you cannot see/adjust the endmill clearance angle anywhere as easily. And the finger needs to swap sides if the grinding forces are to drive the endmill towards the rest.
    b) The tapered roller bearings here are only very lightly oiled, and the pre-load can be adjusted via the brass knob to make them spin freely, or not so much.
    c) You have to come up with a stiff stationary finger rest. And when you think it is built stiff enough to NOT DEFLECT, you will be wrong. And again when you think it is stiff enough, you will still be mistaken. Multiple setscrews are apropos to lock any adjustable features -- thumbscrews will not suffice.
    d) A ground fixture plate is what this was built around because that was what was mounted on the CSG at project start. Finger rest would move up for a mag chuck.
    e) Finger and rotation configured to yield grinding forces always applied towards finger. Position finger to put flute on wheel center or a scosch beyond center. Gotta use a thin wheel or profile a wheel with a substantial relief for N>2 flutes. Else, especially on small diameter endmills, the adjacent flute coming around will get clobbered. A dressed cutoff wheel even works; ended up with a thin diamond wheel to also do carbide endmills.
    f) Concept could be adapted to the traditional SG air-bearing/cup-wheel EM flute fixture that is rotated 90 degrees from the fixture pictured here. But the CSG longitudinal table movement that would be needed is rough and imprecise compared to smoother crossfeed traverse. A decent, non CSG would be in order. But given a decent SG, you would probably just get a decent air bearing endmill fixture too.
    g) Need to grip fixture and 'unload' the spring pressure on the finger when moving the flute off of the rest for the next rotation. The finger will chip a flute face-end if you do not. (Or you have to [re]sharpen the endmill face ends with your chosen method as the last op.)
    h) This ended up as a smaller, better, motorized ER32 Spin Fixture than the Motorized 5C Spindexer depicted on 6-5-2020 in ShopMadeTools.
    On a do-over, would:
    a) save time and start with an ER collet chuck extension w/ straight shank and thru-bore; fit it with thin-section ball bearings in a smaller housing. This would yield more clearance under the surface grinder spindle housing and/or allow use of smaller diameter wheels. The tapered roller bearings used are tall, heavy, and way overkill -- the lightest ball bearings would exhibit lower rolling friction.
    b) extend the base plate to bring it flush with the front of the ER chuck -- allows fixture to
    overhang, still with adequate mag chuck holding surface area. You want holding power so when you bozo jank the finger into the shank, your table lock yields instead of knocking the fixture out of alignment.
    c) definitely get head re-examined.
    Last edited by wbc; 03-29-2021, 01:36 AM.

  • #2
    That looks interesting. I must have missed parts 1 and 2. Can you post the links?
    Paul A.
    SE Texas

    And if you look REAL close at an analog signal,
    You will find that it has discrete steps.

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    • #3
      Nice, I like it. Looks like that might have been an awake in bed at night obsession for a while. So how is the performance on the the finished cut on the flutes? Like a new end mill? I would actually be interested in a short video of this in operation.

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      • #4
        no idea how you move the endmil axially. do you have some kind of table travel?

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        • #5
          dian: Grinder table travels axially, carrying EM fixture. Finger is stationary, causing EM to rotate.

          junkaddict: Nothing beats a new endmill. It can take an endmill that won't cut beans and make it cut reasonably well again. The CNC crowd would hemorrhage with this hack. But it works well enough for manual machines.

          Pts 1,2,3 were posted at same time.

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          • #6
            That's an interesting approach but I have to wonder if there would be a taper issue. How do you set up to grind the secondary relief angle?? I would imagine adjust the finger height.
            Also wondering what kind of finish it leaves.

            It's a lot easier with one of these.

            JL..............

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