You say .005 is nothing? That may be if you are doing carpentry, but any time you are machining something .005 might as well be a foot. If a piston is designed to be installed with .005 clearance (.0025 per side) and you give it another .005 clearance you just increased the clearance by 100%. That is massive. When building engines .005 is an incredible amount to be off. You can’t be off .005 anywhere all call yourself a machinist.
