This reader bought a bunch of pipe clamps and wondered why the directions suggested he buy black pipe instead of galvanized. His black pipes are oily and put black marks on the projects. Why this recommendation?
Simon Watts: Pipe clamps come in two types: one has spring-loaded clutch plates and the other a single, toothed lever. The latter type is less common but it grips black iron or galvanized pipe equally well. The clutch plate variety works best on black iron because it tends to slip on the thin skin of zinc around a galvanized pipe. Protect the work–especially across the glue lines-with strips of wax paper or plastic.
Michael Dresdner: Black pipe is cheaper, and some claim a bit stiffer as well, so you get less deflection in the clamp. I’ve used both and both work adequately. You can remove the oil by wiping the pipe with mineral spirits or naphtha. You can also seal the pipe with a wipe of shellac to prevent black marks on the wood.
Ian Kirby: That’s sounds like an oversight on their part, but it doesn’t much matter. Clean the oil from the pipe for good measure. When you put pressure on the clamp, the pipe will bend into the work. If it contacts the glue you will get a blue-black mark on the wood. Put a couple of two inch wide strips of 1/8″ masonite between the pipe and the work.