That pipe, if the same as here, is more than good enough for pipe clamps. Malleable means it doesn't have enough carbon in it to heat treat to a hard metal like you would want in a chisel. It can bend if you are a graunch artist but for normal clamping are fine. You should be alternating them on each side of a glue up (table or bench tops for example) to balance the forces anyway. If you get pipes that are threaded on both ends you can join them to make a longer clamp with the sockets shown further down the page. Hand tight is good enough and remember to put a pad of thin plywood or cardboard under it to keep it from denting the wood unless you are thicknessing a lot after the panel is glued. Put paper between the pipes and wood to prevent black stains from the reaction between glue and wood. They work reasonably well for putting cases and cabinets together too. I think they are a good and versatile all round clamp.
I started out with a dozen or so Jorgenson Pony clamps in the early 80's and still have them, still using them. Inherited another dozen or so from my father. When the Asian imports came out for a lot less money lots of people bought them but found they slip when trying to tighten. The "spring loaded clutch plates were soft and wouldn't grip the pipe and in some cases wouldn't release. Threads on the handle were poor and rough making for jambs. I doubt they are much better now. As far as I know the Pony's are no longer made and I wouldn't touch the imports with a ten foot pipe.
I would get the Bessey's if I needed more pipe clamps now. I looked closely at them when I worked at Lee Valley last Christmas. They will be less frustrating to use and last a long time, so better value.
Pete
I'll add that you can get the same pipes with galvanizing . The black staining is less of a problem but the galvanizing interferes with the clutch plates gripping.
