Torque wrench

[Gravity Aided]

I think it aids in providing proper and even tension. All kidding aside, it does allow you to do up headset bolts and other critical hardware with an even strain.

 

[Globalti]

You are talking about the mechanic's "feel" for materials. An experienced mechanic knows the elasticity of different materials and can feel when they are tight. For example if he was tightening a nut made from porcelain onto a bolt he would know to stop as soon as it was snug as any tighter would break the brittle porcelain. Tightening a steel nut onto a steel bolt he knows the difference between hand snug, tight and extremely tight where the metal is being stretched. He would also know instinctively when the limit was reached with brass, mild steel, hard steel and stainless steel and how much compression a washer can take although there are very many different alloys of steel so a torque wrench is always a good precaution especially, as others have written, when tightening multiple fasteners.

Personally I enjoy torquing up bolts using a torque wrench, the click as it goes over the top and the feeling that you're doing a proper job and taking time to do it right, is part of the joy of mechanical fettling.

 

[subaqua]

stainless to stainless overtightened is horrible feeling when you do it. because it "Shears " together. you can go further and shear the bolt itself but that is going to muller the materials being clamped.

one other thing people forget is it is NOT the tensile strength of the bolt that affects the torque, or the ductility of the bolt material , but the compression ( ductility) of the material being clamped. copper busbars are relatively soft so need a good torque setting to ensure good conductivity but not overtightened to start compressing and squeezing ( extruding) the copper out

 

[Dogtrousers]

I've got one, but I just use it as a nice quality socket set now. First time I used it I studied the instructions carefully, and tightened up some stem bolts, having first checked the required torque. "Hmmm" I thought. "This is tighter than I would usually do it ... but who am I to argue?" then PING! I sheared the blimmin bolt. Perhaps there was something wrong with the wrench, or perhaps I hadn't done it properly, or perhaps the bolt was already flawed.

Either way, I don't trust it now. So I just use my own judgment as I always have (I don't have any carbon bikes anyway).