Reply by BTKS

Like some of the others have said. Thread both ends of your pipe and couple them when you need longer clamps. I’ve noticed I rarely use a clamp much longer than 4’. Most of the time 1 and 2 foot bar clamps work the best for what I do in the shop. On project sites 3 and 4’ are much more common. I prefer 3/4in pipe instead of 1/2. Much stronger and not much heavier.
Most box stores or plumbing stores will thread the ends as a service, ie no charge. I have gone to steel yards and picked up 20’ lengths cheaper then had a machine / welding shop cut and thread various lengths for me pretty cheap. Two stops but it saved some money and I got to see some guys I knew.
Hope this helps, Later BTKS

-- "Man's ingenuity has outrun his intelligence" (Joseph Wood Krutch)