I've always used pipe clamps, I have 16 of my own & 32 or 33 that belonged to my Dad. & miles of 3/4" galvanized pipe. I have 4 clamps with black pipe which are the last ones used I hate black pipe I always have to worry about the pipe staining something. Being the galvanized pipe is many years old I have no problems with slipping.
"Forget the flat stuff slap something on the spinny thing and lets go, we're burning daylight" Bart Leetch
"If it ain't round you may be a knuckle dragger""Turners drag their nuckles too, they just do it at a higher RPM"Bart