Just as a point of interest, the torque figures quoted by factories are for clean, dry (new) threads (it's reliant on a given friction level). If a thread is rusted / dirty, or indeed oiled (as some people do), the friction level alters (therefore, even with a wrench, the final torque figures can still be "wrong", if you see what I mean).
I recall a gut-wrenching error by a lad working on his mates bike years ago: said lad was a bit of a know-all (his brother was a mechanic), and took a spark plug out. On re-fitting it, rather than heed the advice of other, clued up mates (ie, finger-tight-and-a-fraction-more), he uttered those infamous last words "I know what I'm doing" and promptly stripped the threads from the cylinder head...
I also remember working for a marine engineering firm about 10 years back and had a bloke ask to borrow my Allen keys (not an inexperienced apprentice either, but a bloke 6 month from retiring) to strip a pulley from a trawler. Seized with rust from years of salt water spray it were obvious (to me anyhow) it were obvious it wouldn't move easily. Allen keys came back chewed up (they weren't cheapo things either), and the screws totally unmoved.