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  1. #1
    wb2vsj is offline Hot Rolled
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    Apr 2010
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    Default Source for small D-Shape chassis punch?

    I need to make about 8 holes for some Pomona Binding posts. The posts are D-shaped to prevent rotation. Greenlee's are too big, can't find any on McMaster (not sure I would want to buy one after seeing some of the prices for this small job)

    Is there a simple way to make one? Chassis material is 24ga steel.

    Thanks, Walt
    Attached Thumbnails Attached Thumbnails pomona-d.jpg  

  2. #2
    FishTaco is offline Aluminum
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    AB Canada
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    Default

    Do you know anyone with an EDM that can cut or sink out a punch and die set for you? possibly even a water jet for the die but I don't know what kind of tolerences you need to hold for a die. The punch could be made with a surface grinder.

  3. #3
    JCavalry is offline Plastic
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    Ohio USA
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    Default

    Quote Originally Posted by wb2vsj View Post
    I need to make about 8 holes for some Pomona Binding posts. The posts are D-shaped to prevent rotation.
    If pairs of the binding posts are spaced at the standard (for a double banana plug) 3/4" o.c., Pomona makes alignment strips with two D-shaped holes. Search Pomona Electronics for model 3862 - mounting base, double binding post. Those are black plastic and mount above the panel. Years ago, they sold (and maybe still do, but I couldn't find them) metal alignment strips, maybe 1/2" x 1" 16 ga., with two D-shaped holes that went behind the panel.

    JCav

  4. #4
    Forrest Addy is online now Diamond
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    Dec 2000
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    Bremerton WA USA
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    Default

    I've mounted dozens of tool posts over the years and while its nice to have the D shaped punch to make holes with nice tidy flats, I cheated.

    I either aligned the posts in round 3/8 holes and lock tighted them in place or I blunt punched the hole lip to squash metal into the diameter simulating the flat. Sometimes you have to do a little filing. Either way it's quicker than the chassis punch.

    Practice a little with the punch on remnent metal and you will soon make a neat, workmanlike "D" of the round hole.

  5. #5
    -Chris-'s Avatar
    -Chris- is offline Plastic
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    Nov 2007
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    North Idaho
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    31

    Default Single d punch and die

    Check out cetooling.com they have lots of this kind of tooling -Chris-

  6. #6
    wb2vsj is offline Hot Rolled
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    Default

    Thanks to everyone for their input.

    Forrest, loctite-ing them into place was my first thought then modifying an existing hollow punch came second. Much, much cheaper too!

    I had thought about making a rudimentary punch and die but for this small of a job it's not worth it.

    -Chris- thanks for that site, it has been bookmarked.

    Thanks,

    Walt

  7. #7
    Exptec is offline Aluminum
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    Jul 2004
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    MA
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    Default

    For just 8 holes, drill ~0.350 and finish the profile with small round file and small 3 corner file

    ExpTec
    DBA Experimental Technique

  8. #8
    USMCPOP is offline Titanium
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    Jul 2005
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    Midlothian, Virginia
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    Default

    I've punched holes in thin sheet metal using a regular pin punch. Put a block of wood in a vise with the end grain up then smack the punch with a hammer. Shouldn't be hard to grind a flat on the side.

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