Lens Board Drillig

Discussion in 'Camera Building, Repairs & Modification' started by Wade D, Sep 7, 2011.

  1. Wade D

    Wade D Member

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    I have an undrilled board for my Crown Graphic. A Graflex Optar 135mm in a Graphex shutter is on the way to me. Of course I will wait till I get it to determine the size of the hole needed. I also have a drill press and clamp block. My question is will a fly cutter meant for wood work with aluminum? What would be a preferred bit for the operation without damaging the board?
    Thanks,
    Wade
     
  2. ruilourosa

    ruilourosa Member

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    It will damage your cutter! get one with a titanium tip, not that expensive, they use to be yellow like some black and decker drills, although not that much of a problem!!!
     
  3. Rick A

    Rick A Subscriber

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    Most fly cutters use tool steel, should be okay, just use a slower quill speed and feed it slowly. I use hole saws, but I don't think they are as accurate as fly cutters. Is your cutter a single or double bit? Doubles should work easier.
     
  4. bdial

    bdial Subscriber

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    It will work ok, as Rick says, though it might need a sharpening afterword. You might want to use some light oil.
    Feed the bit VERY slowly, and make sure the board is securely clamped down. If you have some scrap AL to practice with that would be good.

    edit - Just remembered how thin a Graflex board is, you may want to sandwich it between two pieces of wood to support it during the cut, and keep it from tearing out.
     
    Last edited by a moderator: Sep 7, 2011
  5. paul ron

    paul ron Member

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    Hole cutters n fly cutters aren't accurate and will make a lousey job of your board, they wobble n are never on center. Better to cut the hole undersized with a hole saw then file it to the finish line.
     
  6. Ian C

    Ian C Member

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    The clearance hole for a shutter must be accurate. If you examine the threaded retaining ring for a modern shutter you might be surprised at how little difference there is between the diameter of the treaded shank of the shutter and the outside diameter of the retaining ring.

    The hole must be slightly larger than the shank, but must be no larger than necessary so that there is enough material left for the ring to grip the lens board.

    Machining a shutter clearance hole is a job best done with a single point cutting tool in milling machine. These have precise bearings that allow no unwanted radial movement (within practical limits) of the spindle as it rotates.

    In contrast, a drill press has a much simpler bearing set that allows too much radial movement for precision work. Older drill presses that have seen much use often have bearings that are worn allowing the spindle considerable radial movement. Accurate work is impossible.

    If you don’t have access to a milling machine, it’s prudent to send the board along with a precision measurement to a machine shop. If the hole is machined oversize, it will be spoiled for the shutter size you intend.

    I machine aluminum boards on a Bridgeport milling machine using a single-point high-speed steel cutting tool. I always take a test cut in a piece of scrap to verify the hole diameter it produces before machining the lens board.
     
  7. John Koehrer

    John Koehrer Subscriber

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    On the other hand, both hole saw and fly cutter will work.
    The tolerance on some can be higher than others, in addition, some flanges may have a lip that should insert into the hole to position the lens.
     
  8. waynecrider

    waynecrider Member

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    I use to take mine to a local machine shop I found.
     
  9. rjbuzzclick

    rjbuzzclick Member

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    I've done a couple of SG aluminum lensboards-smaller holes with a Greenlee punch and some filing, and one larger hole with a lathe, which worked OK, but the edge of the hole ended up with a lot of burr material that had to be cleaned off.
     
  10. Jim Jones

    Jim Jones Subscriber

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    A really sharp lathe tool ground to the right angles should make a clean cut. Backing the lens board with scrap material will also help. If you do have a burr, scraping it off with a sharp right angle tool can be quicker and neater than filing. Sometimes a metal ruler works for this.
     
  11. jp80874

    jp80874 Subscriber

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    Wade,

    Either I have been very lucky or the above posters have made this task far more complicated than I needed. If they already have the tools, that is good use of them. I have had to do it this way because I don’t own some of the sophisticated cutting tools mentioned (lathe, Bridgeport). My only experience is with Sinar aluminum 5 ½” or 14cm boards. I have drawn the size hole needed on the lens board, clamped it in a vise using wood on either side for protection, drilled multiple smaller holes well within the drawn circle, used a saber saw to rough cut a circle smaller than the one needed, and then an appropriately sized sanding drum on a shaft in the drill to grind out to the size needed. I have checked often to be sure the circle I am cutting is round and within the size needed. As with hair cuts, one can always cut more, but never put back.

    When I first needed a hole cut I checked a local machine shop and found a basic set up fee of $75. Some of the specialized photography machinists were more expensive. I bought a set of sander drums for about $10.00.

    John Powers
     
  12. paul ron

    paul ron Member

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    Sure sanding or filing is all you really need to do, just do it carefully to the finish line and it will be just as good as any machined hole.

    .
     
  13. Wade D

    Wade D Member

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    Thanks for all the tips. Sending it out for milling would be too expensive for this project.
    A friend has a nibbler tool used to make holes in aluminum electronic chassis boxes. I might try that on a piece of scrap and see how it does. Too bad I don't have access to the laser lab at the place I retired from. It would make quick and accurate work of this.:smile:
     
  14. Leigh B

    Leigh B Member

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    Same here.

    The hole needs to be larger than the shutter threads by a significant amount on modern shutters. If you examine the retaining ring on the side toward the shutter you'll find a shoulder. This should go inside the hole, and it determines the correct hole diameter.

    - Leigh
     
  15. Dan Fromm

    Dan Fromm Member

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    Right, except for really thin boards like those for 2x3 Pacemaker Graphics.

    Holes drilled the right size in these little gems allow the edge of centering ridge (that's the shoulder you mentioned, Leigh) to bear directly on the back of the shutter. The result is a shutter that will turn freely on the board with the ring tightened. Darkroom tape around the back of the retaining ring holding it to the board -- not between board and retaining ring -- solves the problem. Using a retaining ring from a Copal-Polaroid MP-4 #1 Press shutter, which doesn't have the ridge, also also solves it but then centering the shutter in the hole is difficult.
     
  16. Leigh B

    Leigh B Member

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    Yes, Dan,

    But if I said "centering ridge", nobody would know what I was talking about.

    The first rule of communication is to address your audience using terminology that they understand.

    - Leigh