At the co-op a couple of weeks ago I was preparing an old (1970's?) Columbia for sale. Its stem was raised up abnormally high so I loosened the bolt to drop it down to a more "normal" height. It would not budge. I sprayed it liberally with a penetrating lubricant, pounded on it with a mallet, added more lubricant and let it sit while I trued the wheels and cleaned up the rest of the bike. With nothing left to do I took up the stem issue again thinking (hoping?) that the lubricant would have worked its magic. No dice. I drag over a shop mentor and he takes several wacks at it to no avail. Finally he drags the thing over to the angle grinder and starts cutting off the stem. The vibration from the power tool actually did loosen the stem but by then it was too late.