Nope - it's not just 14mm. Either engineers today don't know what they're doing (suspect), or they're using the wrong tables. I could calculate this by hand without looking up T=c*d*F, and we designed the F load.
Anyway, 14mm (0.5512 inch) is closer to 9/16" (0.5625 inch) than 1/2" (0.5000 inch). So look in the SAE Fine Thread table below (the bottom table) at 9/16" threads. Go from left to right from weakest to strongest grade of steel. Torque specs are not constant for a single thread size! They range from 73 ft-lbs to 201 ft-lbs.
You HAVE TO know what type of steel the bolt has. Or you'll under-torque, risking it coming apart, or over-torque and snap the bolt head off. Or hope to god the junior engineer assigned to the task has someone somewhere guiding them. That is usually no longer the case anymore.
Addendum: this chart is from Fastenal, a major worldwide fastener supplier. We used them almost exclusively at one point - no counterfeit issues.
Also I see I'm obsolete, no surprise, SAE Grade 2 has become ASTM 307A, and what the high grade was is now FNL Grade 9, used by aerospace and military.
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