Square Drive Screws and Drivers
These screw types have a "+" shaped recess on the head and are driven by a cross-head screwdriver, designed originally for use with mass-production mechanical screwing machines. There are a few other recessed drive screws presented that you also want to be aware.
So, why all the confusion? Why all the damaged screw heads and drivers? Why is this screw and driver thing so awkward? Read on and be amazed while I unravel the mystery of screw drives and present some you may have never seen.
For each screw drive type, from ancient Slot through to space-age Lox we present a quick view of the screw head, the drive name, a picture of the appropriate drive bit, followed by an explanation of the type. Also presented are the advantages and disadvantages of each drive type. Slot type are also included because that is where the screw began and a double slot becomes a cross drive, and the Robertson or square drive enter the story with recent combined Phillips/Square drives. The Allan, Spline, Torx etc drives are not included and maybe neither should the Uni-Screw, it is just so darn new and interesting.
This article contains a lot of information and pictures from the Internet. Maybe it will be the definitive guide with your help it could get close. If you disagree with any of the information or if I missed a related drive you know of, please let me know where I can validate the information. Misinformation, incorrect illustrations, screwed up usage of terms on the Internet and elsewhere is rampant and part of the problem created by so many drives.
First a little background:
A screw is really a shaft with a helical groove or thread formed on its surface. Its main uses are as a threaded fastener used to hold objects together, and as a simple machine used to translate torque into linear force. It can also be defined as an inclined plane wrapped around a shaft.
Every threaded fastener needs a way of turning it. Whether a wrench fits a hex-head bolt or a nut, or it may have a shaped and recessed hole into which a driver can be inserted.
Step 1: Early Screws
Metal screws and nuts used to fasten two objects together first appeared in the fifteenth century.
In 1770, English instrument maker, Jesse Ramsden (1735-1800) invented the first satisfactory screw-cutting lathe. Ramsden inspired other inventors. In 1797, Englishmen, Henry Maudslay (1771-1831) invented a large screw-cutting lathe that made it possible to mass-produce accurately sized screws. In 1798, American David Wilkinson also invented machinery for the mass production of threaded metal screws.
The screw on the left (A) was handmade in the late 18th century. Note the flat spot on the shaft, the irregular threads, blunt tip and the off center slot. The screw in the center (B) is machine made around 1830. It has sharp, even threads, a cylindrical shape, blunt end and the slot is still off center. The screw on the right (C) is a modern gimlet screw, post 1848, with tapered shaft, even threads, pointed tip and centered slot.