Is schedule 80 1" pipe the same as the black iron pipe you would find at the big box store ?

Usually you find schedule 40 at lowes depot. The schedule rating is wall thickness. Shedule 40 and 80 1in pipe will both be 1" ID the OD is what varys.

Iron Pipe sizes remain the same on the OD regardless of schedule. The higher schedules have thicker walls, always taken up on the ID. This way standard threaded fittings work on various schedules of pipe.

Tube sizes are measured by ID .

The size designation is the nominal size, neither the ID or OD of 1" pipe measures 1"

If you are buying pipe for forging , It's best to specify domestic grade as it seems to be less prone to splitting at the welded seam. This is not what is usually available at big box home centers.

The very best pipe for hot forging is schedule 160 DOM [drawn over mandrel ] which is seamless. Expensive stuff and not always easily available.

That helps, thanks guys.

Good luck with that, domestic pipe is hard to find these days. The stuff usually found in stores like Lowes & Home Depot is probably A120. A53 & A106 are better grades and less likely to split. The grade is usually marked on the pipe.

My local steel yard stocks uncoated pipe (no paint), if you are going to be forging a lot it's worth looking for as the paint on black iron smells nasty as it burns. DO NOT use galvanized pipe, the toxic fumes could kill you.

And plug the pipe to prevent it conducting hot gasses from fire to your hand, if using a coal forge to heat the end.
And be careful quenching. the pipe could create a jet of steam or boiling water at you.

And if your ID is bigger than your OD, then your pipe is inside out :-)