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1 1/4 NPT though Cast iron

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  • Doozer
    replied
    Trying to wrap my head around the need to drill a hole in the K&T machine base.
    Presumably there was some way the factory ran the wires.?!?!??
    Seems like going the long way around the barn.

    -Doozer

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  • Beazld
    replied
    If you are running conduit into a machine base and not concerned with explosion proof, why not a clearance through hole for the conduit and a couple lock nuts, one inside and one outside and call it done? No need to tap.

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  • outlawspeeder
    replied
    Sorry no gas main. It is a base to a machine and no place for a mag drill. If I lay my drill press on the floor and then use a jack to lift it to the right height. I could put the base of the drill press on the other side of the mill... It still wouldn't work hahaha. I am just going to have to put may back into it.

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  • David Powell
    replied
    ooh, please can I watch from a distance? Regards David Powell.

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  • Doozer
    replied
    Or midnight tapping into an underground gas main.

    -D

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  • reggie_obe
    replied
    Originally posted by garyhlucas View Post
    Sounds like he is working on an explosion proof enclosure..
    Sounds to me like he's drilling a cast iron machine base.

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  • garyhlucas
    replied
    Sounds like he is working on an explosionproof enclosure. The tough part is that the sides are likely sloped but it will have only flat mounting tabs on the back and a ground front face. So no place to use a mag drill. I've done them in a floor standing drill press by swinging the table out of the way and using a spacer or lowering the drill head. If you can clamp it all down you can use a center in the spindle to keep the tap straight as you turn it with a big wrench.

    Interestingly I could do this easily on my homebuilt CNC minimill. That's because I can rotate the spindle to make it a horizontal machine and the table is stationary. So I could circle interpolate the hole with an end mill and then thread mill the threads. Thread milling large tapped holes is just plain awesome.

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  • 754
    replied
    If you use the magdrill , you can put a center in it to start the tap.l

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  • outlawspeeder
    replied
    What I got, rent a mag drill if there is a flat spot. Use a hole saw. Go slow 50 RPMs. Don't let it spin my arms off if it grabs. Tap will work, use big tap handle.

    Time to go shopping.

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  • nickel-city-fab
    replied
    Hole saw and a fresh pipe tap will work fine. I've done stuff like that before, just take it slow and careful and don't cram the work.

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  • JohnMartin
    replied

    Agree that a holesaw is probably the best option. But for just one hole, sometimes you have to go with what you already have.

    Got a piloted counterbore of about the right size? Back up the cast iron with something for the pilot - even a piece of wood - and it should do the job. If it’s too small, do you have an adjustable reamer to finish the hole?

    Might even try one of the adjustable arm type hole cutters. The ones that look like a piloted fly cutter. I don’t think I’d try it on steel, but cast iron isn’t too grabby. Cut small, finish with a reamer if you have one.

    Hole size is not critical. If you can get the tap to start in it, you’re fine. A tapered thread pipe tap acts somewhat as a reamer anyway, as it cuts the full depth of the hole the entire way.

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  • CCWKen
    replied
    Yep, I've used a 2 1/2" bi-metal hole saw in 1/2" A36. Not a breeze but sure beats drilling a bunch of holes in a circle and trying to tap that. (Do you see me rolling my eyes?)

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  • wierdscience
    replied
    Bi-metal holesaw is the way to go, and cast iron will drill much easier than steel which is a plus. By holesaw, we mean a good one , Lennox, Starrett etc. Tapping won't be too bad, if you are just threading it for conduit, you can probably go a little larger than the recommended tap drill for 1-1/4 NPT and be fine.

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  • Mcgyver
    replied
    thats a point, it would be the easiest way out. I've not used one on cast iron, you'd want to make it was flat enough to get a solid grip

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  • CCWKen
    replied
    Isn't there any Rental Shops in your neighborhood? You don't have to OWN a freekin' mag drill to use one.

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