Dumb torque question (and metric size question)

[LVDell]

So I have a M14 bolt. Does that mean it is a 14MM socket?

Also, the tightening torque for the bolt is 100Nm (74 ftlb.) + 90 degrees. What exactly does that mean? I assume it is 100Nm and then at the "click" continue for 1/4 turn of the torque wrench? If so, then why not a more specific reading? Unless there is less than 1Nm in a 1/4 turn I don't understand.

TIA for the help! Boy do I feel stupid :cursing:

Edited May 5, 2006 by LVDell

[wvicary]

14mm is the diameter of the bolt. You then tighten the bolt to 100nm plus 90 degrees but don't use a torque wrench to go the extra 90 degrees. You can damage the torque wrench by going past it's limit or setting, buy yourself a straight bar or power handle.... they go by different names. The type of bolt your dealing with is known as a "torque to yeild" and are very common these days. Often this type of bolt is a one time use only and must be replaced each time.

[LVDell]

So, then I torque it to 100Nm and the using a non-torque wrench tighten 1/4 turn more?

Thanks again!

[0586slb]

As said above, an M14 bolt is a big bolt, where the 14 is the thread diameter in millimeters. Typically, an M6 uses a 10mm socket, an M8 a 13mm and an M10 either 17mm or 19mm.

The extra ¼ turn actually stretches the bolt. Virtually all torque to yeild bolts are single use as when they stretch, they exhibit plastic deformation and will snap if torqued again. Be sure to do the ¼ turn without stopping - there are also protractor discs that slip over your socket drive so you can accurately measure the turn.

[LVDell]

Just finshed. Thanks for the help guys!