How good are you at eyeballing hex fastener sizes?

[Corndoggeh]

Anything that is from 10 - 15mm and 1/2" to 3/4" I get right 9 out of 10 times. Anything else just depends on if I'm daydreaming about boobies or not.

 

[MushCreek]

SAE- close to 100%

Metric- 50/50

SAE socket head (Allen wrench)- 100% (they're used extensively in my trade)

Metric socket head- 30%

 

[Heavy Metal Doctor]

Here is one for you

Water valve / meter box bolt, right? I see the 5 point sockets on water department service trucks often.

 

[Bessy]

Probably a 7 in 10 on SAE stuff, My Dad and I had a bit of a competition the other day on this very subject while adjusting the valves on the 120 Lehman in the boat, I had never even worked on that engine and I called all but about two fasteners. both times I was off by about a 1/16th of a size. Dad on the other hand is the self proclaimed worst socket picker ever.

When I replaced the head gasket in the green demon (John Deere D110) I was at best 7 in 10, as there seems to be a mixture of metric and standard fasteners on that mower.

 

[jeffmoss26]

Just use your eye-crometer.