Hi there, there is something I would like to ask.
According to the chart of allowable shear stress (http://www.tokaibane.com/images/tech_coil2_05_ill.gif), the allowable shear stress value shown in the figure is about 50% of the tensile strength. Similarly, according to the chart of allowable bending stress, (http://www.tokaibane.com/images/tech_coil2_06_ill.gif), the allowable bending stress value is about 70% of the tensile strength. I think 70% of the allowable bending stress is the yield ratio, why the allowable shear stress value is about 50% of the tensile strength.
Thank you for your inquiry, TETSU!
The allowable shear stress is the value obtained from spring’s experimental data.
In addition, the value is slightly different for each material.
For example, it is 50% for piano wire and hard drawn steel wire, 55% for oil tempered wire and 40% for stainless steel wire.
