"Tip from a real mechanic ( not me....a former boss of mine!).....if you've got a slightly oversize spanner (wrench) use your feeler gauge set to fill the gap... useful when Metric, UNF, and BSW/BSF co-exist"
Met a few of these "real mechanics" during my 40 odd years doing the job. They usually have a superb set of large hammers combined with numerous bent screw drivers used in lieu of chisels or levers. They also tend to have socket extension bars that don't fit anymore because they have been used as punches. A collection of bike spanners is also a must. Personaly I just prefer to buy the right tool for the job so as not to leave the next poor b*stard with a problem.