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Thread: Drill Jigs

  1. #21
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    Quote Originally Posted by vmipacman View Post

    Question for those who used jigs heavily in the past. What was the process for tapped holes? was there another jig with threads so that a tap could follow something accurate into the hole?

    Thanks
    Most of the time we removed the part from the jig and used tapping heads on the drill presses. In a few cases, we had slip bushings in place to drill the hole and pulled the bushing and tapped the hole. Same process for drilled then reamed holes.

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    Just to clarify a bit, the slip bushings (to allow tapping with the jig still in place)
    are not sized to guide the tap, just clearance for it to work.

    I have designed many drill jigs, and not a single one made to guide a tap.
    Others may do this, would be nice to hear other views.

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    Just to clarify a bit, the slip bushings (to allow tapping with the jig still in place)
    are not sized to guide the tap, just clearance for it to work.

    99% of this work was done on radial drills, and once the spindle was positioned over the hole, you didn't want move it again for tapping, countersinking etc.

    So you have the drills, the taps, the countersinks, etc. all set up in quick change toolholders.

    Once in position, you do every operation needed on that hole, then move on.

    I have designed many drill jigs, and not a single one made to guide a tap.
    Others may do this, would be nice to hear if someone does.

  6. #24
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    Quote Originally Posted by digger doug View Post
    99% of this work was done on radial drills, and once the spindle was positioned over the hole, you didn't want move it again for tapping, countersinking etc. (my time yes, real old time prolly no)

    So you have the drills, the taps, the countersinks, etc. all set up in quick change toolholders. (my time yes, real old time prolly no)

    Once in position, you do every operation needed on that hole, then move on.

    I have designed many drill jigs, and not a single one made to guide a tap.
    Others may do this, would be nice to hear if someone does.
    About the tap bushing It’s been a long time but my recollection is the same as yours. The hub & wheel jigs were piloted, and when threading (the hub) the jig was removed & the radial drill guy just tapped by locating the hole with the spindle in reverse, settling the drill & go spindle forward (press down).

    On the every tool after drill located & locked I guess it depended. At the heavy SAE shop I was at the radial operator started at CAT in the 30's & hired on in this shop late 60's. He'd sometimes drive around unlocked (with jigs) then go back the same for each tool and sometimes station & lock and switch tools with the spindle running. He handled the 5' italian radial like a switch blade, the 9' (new) eastern europe built one with electric locks he generally locked it. The old fart could fill a pallet with onesie-twosie's to tensie's in a day, a lot of them laid out at his bench & punched.

    I can check with an old OMC guy if I can remember. They had pallet rack full of jigs left from carburetor & small parts that were run (some to the late 60’s) on long table drill lines where the jigs were passed operator to operator. It was cool to look at some as they’d have angled bushings (more drill angles than just the 6 sides of the box jig). That meant the operator had to have an angled nest at their station.

    Good luck,
    Matt

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    Quote Originally Posted by Ox View Post
    I completely understand that.
    I have used them on transfer lines and smaller projects as well.
    I'm old enough to have used drill bushings and such....

    But what I don't understand was the fact that if the part is too funky for a fixt .....

    aw heck, forget it ...
    If I'm understanding the OP correctly, building a fixture to hold the part on a mill (or even a drill press) in the correct orientation/rigidity, etc. would be very difficult. Instead of building a fixture, they want to build a drill jig that they can fasten to the part and drill the holes.

    I've done this before on bolt patterns that were in awkward locations on a large weldment. The cost of setting the weldment up on the big mill, often at an angle, would be quite high. I could make a simple disposable drill jig with a Bridgeport, c-clamp it to the weldment, and put in the holes I needed in much less time and spending much less money.

    Quote Originally Posted by Ox View Post
    Suffice to say that for a drill bushing to be of any use, not only does the bushing need fixtured, but so does the part.
    One fixture in a CNC with use of a center drill is half of the fixturing that needs done to a part that is
    The part often doesn't need to be fixtured (i.e. held in a special way), you often just have it sitting on the floor. The drill jig, which holds multiple bushings in the correct pattern, is clamped to the part, often with c-clamps or clecos (Welcome to Cleco Fasteners by MRO Tools +). On some parts, the drill jig will locate off one or two edges of the part.

    Quote Originally Posted by Ox View Post
    AFAIK "jig" is synonymous with "fixture".
    If this is not so - please edumacate me!
    I my experience in the aerospace world*, that's not usually the case. In general, the fixture holds the part or parts. The drill jig holds bushings for drilling the holes. A rough example if we were riveting two parts together.

    1) Clamp parts A and B into a fixture that holds them in the correct alignment.
    2) There are some undersized holes pre-drilled into A and B. Using these holes, attach the drill jig to the parts using clecos.
    3) Drill the holes. This can be done with a hand-drill or a self-feeding (e.g. Quackenbush) drill. You now have a bunch of holes match drilled through both parts.
    4) Remove the parts, deburr, apply sealant, etc. then put them back together and rivet them.

    * I'm talking about aircraft here, the satellite guys are a whole different ballgame. They call the thing that holds the parts ground support equipment, and use drill jig and fixture interchangeably. Then they call the equipment to talk to the satellite once it's in space ground support equipment as well... and they don't use safety factors, they use margin of safety...

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    And to answer the OP's question. Assuming the pattern only has to be good to itself, a drill jig to +-.005 sounds easy. If you have to locate the patter with respect to something else, you'll either need an edge, pin hole, or put laser tracker nests on the drill jig (although that would eat up quite a bit of your tolerance.


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