1 1/4 NPT though Cast iron

[garyhlucas]

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.

[reggie_obe]

Sounds like he is working on an explosion proof enclosure..

Sounds to me like he's drilling a cast iron machine base.

[Doozer]

Or midnight tapping into an underground gas main.

-D

[David Powell]

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

[outlawspeeder]

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.

[Beazld]

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.

[Doozer]

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