I suggest you check out the Bennett Mechanical Aptitude Test (BMCT). It is 68 questions, all multiple choice regarding simple picture type problems (levers, gears, pulleys, etc), and takes about 30 minutes for the actual exam.
My experience with most paper testing is that it can't tell you who will be the best candidates, but it can readily identify a lot of those who are poor candidates.
Edited to Add: BTW, as far as paper testing goes, after looking at math, reading, english, and BMCT scores for welding students over several years it appears to me that a very good indicator of potential for mechanical work is simply reading comprehension level. That was kind of a surprise to me but it also seems to make sense... How well can a guy understand what he is looking at / process information? If a guy's reading comp is low, I would not be surprised with issues during tasks such as layout, fitting, computing bends, blueprint reading, and general understanding of all types (including mechanical comprehension). It may indicate that a guy is going to have problems usefully processing and applying new information on his own.
Again, paper testing is limited in what it can tell you... it is quite possible for a good sharp guy to do poorly on reading tests. But overall, while it may not tell you who will be the best candidates, it may be useful in identifying some of those who are most likely to be poor candidates.
Tim,
My welding started being a private in the US Army welding instructor and includes managing a wet welding job with a situation 2 good at / 14 in between / 4 got cartridge tools in that they "couldn't". You are looking for manual dexterity / eye hand coordination. At a large overseas facility I seen train aids to promote such without an arc. My guess is that such is available commercially. The groups that comes to mind are the exceptional pin ball players / digital came players and surgeons! I would suggest not waiting for the surgeons to show up. I hope this is helpful.
Len Andersen
Construction Project Manager
New York City Department of Transportation (NYCDOT)
Division of Bridges
55 Water Street – 5 th Floor WS-05-3F
New York, New York 10041
landersen@dot.nyc.gov
212-839-6599 / FAX 4042 / Co Worker 6381