Socket extension and screw friction force 1

[hansforum]

Hi all,

If we use long socket extension (comparable to the length of the breaker bar or ratchet) to tightening lug bolts on a car, are we creating greater frictional force underneath the bolt head and in the threads because of the torque that is created that wants to bend the bolt head (torque 1 in the sketch) .
I made a sketch (in attachment) to illustrate what I mean. Torque 2 is rotating the bolt and Torque 1 is bending the bolt. Compared to situation without the socket extension, where bending torque is smaller do we need to adjust the torque on the torque wrench differently because of that?

Thanks.

 

[racookpe1978]

You should not have any torque through radius "R" (the hypotenuse of the right angle formed by the torque wrench handle (what you call a breaker bar) and the torque wrench socket extension because you SHOULD BE restraining motion with your other hand by holding the torque wrench properly. Thus, with one hand preventing motion of the socket wrench extension, there will be no extra torque.

 

[tbuelna]

As racookpe1978 noted, proper technique would mean making sure the extension is kept aligned with the fastener. If the extension is kept in alignment with the fastener, then the only effect of using a long slender extension is torsional wind-up in the extension. The amount of wrenching torque applied to the fastener would still be the same.

 

[hansforum]

Thanks for the answers. Sometimes is hard to have proper technique when high force has to be used and if body is in awkward position. Longer torque wrench would definitely help because smaller force would have to be used and therefore create smaller bending torque on the bolt head.

 

[Tmoose]

Adding a universal joint near the lug bolt will require a two handed technique, prevent poor technique and the tendency to tip or twist the socket off the head of the lug bolt.

As mentioned by others one technique involves cradling the head of the breaker bar with one hand, as sort-of shown here.

http://www.ozhonda.com/gallery/data/2/medium/3IMG_4957.jpg

 

[Screwman1]

The other thing that is happening is that for a moment to be applied large enough to cause an adjustment you would be looking at several hundreds of pounds of side load, enough to actually flex the shank of the bolt. When you are using a torque wrench your clamp load accuracy is only about plus/minus 25% or so. Torque is not the most accurate way to determine clamp load, but it's handy, especially on something like lug nuts where they may be installed in less than optimal conditions. Any type of hand torque, no matter how crude is better than 'Bubba" with his impact wrench.