A plot of the efficiency of a (power) screw versus helix angle. Based on plot from <a rel="nofollow" class="external autonumber" href="https://books.google.com/books?id=08FkBSjG2bMC&amp;printsec=frontcover#PPA252,M1">[1]</a>.
<a href="//commons.wikimedia.org/wiki/User:Wizard191" title="User:Wizard191">Wizard191</a>
CC BY-SA 3.0
<span class="int-own-work" lang="en">Own work</span>