Tom, N0SS, wrote: My shack is always climate controlled and although I don't SEE any deterioration of the screws, I HAVE certainly found that the screws do NOT want to be removed if you really tighten them down. Nowadays, I just 'snug' down the screws I remove frequently. They stay tight, and won't voluntarily back themselves out, yet they can be readily removed by the right-sized screwdriver.
----------------------------------------- One of those "Aha!" moments one gets sitting in a class that sticks in the mind for a lifetime is this: A screw is a SPRING! A screw "tightens" because it is a spring. I watched a demonstration of just how important that is. The demonstration consisted of trying to tighten a screw made from frozen Mercury (which is not elastic or "springy"). One can put hundreds of inch-pounds of torque on the darn thing tightening it in a frozen Mercury nut, then remove it with nothing more than your (heavily gloved against the cold) fingers. When a normal screw (or bolt) is tightened, it stretches. That's the "spring action". The threads bind against the mating threads and the head is held secure by whatever is being "fastened" and the whole thing stretches slightly. No stretch, no tightening action. Any action, corrosion, dissimilar metal action, etc., that takes place where those threads are hard-pressed against the mating surfaces will increase the friction enormously. Consider just how long that mating surface is on the screw - it's the entire length of the thread winding around and around the screw that it touching the mating threaded surface. It doesn't take a huge increase in the friction to make the torque required to free it exceed the strength of the shaft, and suddenly you have a broken-off screw. The screws in things like my K2 case are just gently "snugged" down with the proper size screwdriver. Nothing I'd call "tight", and not a single one has ever been found loose the next time I opened it up. A little snugness provides plenty of spring tension to hold the assembly together. How tight do I mean? Well, I've never managed to strip the threads in the slots on the sides of my KPA100 heat sink using the normal Elecraft screws, even though I've removed it dozens of times, at least, over the past few years. Ron AC7AC _______________________________________________ Elecraft mailing list Post to: [email protected] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
