I learned to measure things at my dad’s sheet metal shop. Two things about working with sheet metal and my dad: metal doesn’t change dimensions much with humidity; and a 10th of an inch is close enough but hardly fussy.
Ever since I started working with wood, I’ve had problems: wood, at least along 2 out of 3 axes, does change dimensions with humidity, and a 10th of an inch is way less than the amount the width and thickness of wood change as it dries and absorbs moisture. I keep telling myself not to cut things so tight, and I keep cutting it too close anyway.
Current case in point: this oak door I made for the brick oven:
Weeeell, I was shooting for about 3/8″ of clearance on the sides, which I more or less achieved – during the heat and dry of summer. Should have shot for 1/2″ at least. One problem is that the old, recycled bricks that form the arch into which the door fits are hardly consistent and smooth. They have uneven surfaces even apart from any inconsistency in my brick work. My 3/8th” theoretical clearance was not achieved in practice.
So: While it rained maybe a week before, had a few nice days over Thanksgiving and the almost 22 year old son was in town only a couple days before his birthday, and so was thinking about firing the oven up. The door, while maybe a bit snug this summer, at the time still fit without too much falderal.
When we last used the oven, we left the door in. On Friday, it had swollen to the point of complete immobility. I yanked. I pushed. I wiggled. Nothing – stuck so that any more force seemed likely to break it.
Found a little fan, ran it for a day straight – nothing. I’m considering seeing if I can whack it from the inside with a sledge stuck down the chimney (kind of doubt it). Seriously getting worried it may destroy the brickwork if it swells any more.
If I ever get it out of there, will trim the sides a bit – and store it somewhere dry for the winter.