Henry Maudslay invented a larger screw cutting lathe that made it possible to mass-produce accurately sized screws. At about this same time in America, a machinist named David Wilkerson was inventing a similar machine for mass producing metal screws. These screws were all straight slotted. In 1908, PL Robertson produced the first recess-


drive type screw with a square-drive head. This type of screw was an improvement over the slot head because the screwdriver would not slip out of the screw head during installation. The early model T car used over 700 of Robertson’s screws. In 1932, John P. Thompson patented a screw that had a cross recessed in the head and the matching tool for its installation. Thompson had trouble getting investors for his invention during the Depression, and in 1935 sold his patent to businessman Henry Phillips. Auto manufacturing was now using the assembly line and they needed screws that could take greater torque and could provide tighter fastenings. The Phillips head screw was compatible with the automated screw drivers used in assembly lines. Another screw type featured a hexagonal hole in the head and was produced by William G. Allen of the Allen Manufacturing Co. in Connecticut. Yup — the Allen wrench.


NUTS!


Nuts and bolts were invented in as early as the 1st century by the Romans who used them for building chariots and other magnificent structures of their empire. The first nuts and bolts had square heads, unlike the ones used today that are hexagonal. When machinists used cast iron and cruder forms of steel, square bolt heads were easier to make. As machinery became smaller and more compact, the hex-head bolt evolved to meet the need for more compact bolt heads. By the 1880’s, when steel mills began producing new mild steel in accurate thicknesses and quantity, cold-heading machines began punching out hex-nuts. This allowed the nuts to be stamped out in quantity from flat metal stock and machined to exact tolerances. The new screws and bolts that were being produced in the country now had a partner to secure them. The wars of the early 20th century forced greater


standards on the manufacturers of war equipment. The hex-headed bolt and nut fastener system became essential to not only the war effort, but to every aspect of our modern lives.


14 HelicopterMaintenanceMagazine.com April | May 2020


BRING ON THE WENCHES Oops, I meant “wrenches.” Obviously, wrenches have been around as long as there have been screw threads. As I mentioned earlier, back in history, a screwing device was used to press grapes for wine and to clamp two pieces of wood together to make a clamp or a jaw. There was usually a bar or piece of wood permanently attached perpendicular to the screwing device and used as a lever for turning the screw. In the case of machined bolts, you can’t have a handle attached to each individual nut and bolt. You must have a portable, universal means of turning the threads on the hardware. Let’s talk more about the modern-day concept of this lever.


The first modern day wrench was called a spanner


and was invented by Solymon Merrick in 1835. He received a patent for it in 1842. It had an “S” shaped handle and a straight angle. In the early days, it was made from wrought iron. All of the modern combination wrenches evolved from this one. Later on, an American named JJ Richardson, of


Woodstock, VT invented the ratcheting socket wrench with interchangeable sockets. He received a patent for it in June 1863. The “monkey” wrench was invented by Charles Moncky in 1858, and a patent for the pipe wrench was given to a steamboat fireman named Daniel Stillson in 1870.


A ratchet wrench invented by Robert Owen


received a patent on September 9, 1913. I don’t know the date, but a version of the modern adjustable end wrench was invented by Johan P Johansson from Sweden. Johan worked for the BAHCO corp., the parent company of the future Snap-on. The name that is commonly used for this wrench is “crescent wrench” is derived from the Crescent brand owned by APEX Brands Toolgroup, LLC.


PRECISION MEASURING TOOLS The industrial revolution brought us the production line and the need for standardization and repeatability. To meet and to guarantee the design specifications, it was necessary to develop measuring instruments that would ensure this standardization. The micrometer was


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