All over the 19th century, the most often employed forms of screw head (that is certainly, push styles) have been very simple interior-wrenching straight slots and external-wrenching squares and hexagons. These ended up easy to machine and served most applications sufficiently. Rybczynski describes a flurry of patents for substitute travel https://deanlkgxm.blogtov.com/10981053/5-essential-elements-for-wood-screws