Here we go again on the subject of friction between steel surfaces. I agree with BigInch on this point. Friction factors vary vastly dependant upon the condition of the surfaces. In an industrial situation steel to steel can be as high as the 0.8 value given by RobinHandy. What amazes me is the insistance on certain Companies to adopt the value of 0.3 for steel to steel friction factors for situations where , for example, the pipework is located on an offshore platform. It might be 0.3 for the initial installation but after a few years the friction factor would be well above 0.3. When you bring this up and say the assessment is incorrect using 0.3 the response is generally "That's what we always use" .