I have been doing som calculations on threads for an welded and machined assembly. And the book states that μ (friction) when dry can be between 0,18 to 0,35..
I then did my headscratching and got all the formulas down, did the numbers, found and fixed some errors and summed it up. And i still managed to get some very big and not likely numbers.
And after a hunch i check my other book containing a much more comprehensible table with friction for all the different materials and instances. And that book states steel on steel friction when dry to be 0,1...
Is there something i have missed? I also believe there is even better tables with the surface finish coming into play. But anyway, the difference between these two books is massive.
I once had a online calculator linked to me by someone here. But i lost it. So im hoping something like that comes up again.
If your really interested here is the info.
M24x3
Force is 15000N
calculating without lubrication
Head friction/plane surface not included (im doing the other part in the assembly)