In Britain, the cradle of precision engineering, punctilious motor engineers even insisted on a specific brand of fag paper when checking on the moment contact breaker points opened. If you can just pull Green Rizla papers free, the clearance is one and a half thou. The opposite of fag paper clearances would be shirt sleeve fit. I suppose it is stating the obvious but too little clearance is as bad as too much. Stuart (I try to do things right) Tallack writing a few miles from Sir Henry Royce's home in Sussex.