As bolt sizes finally became standardized, a small complement of single-size wrenches was all that was needed to service all of the common-sized bolts in use. Evolution of the single-size wrenches continued further, outfitting the opposite side of the wrench with a "box" end that completely encircled the head of the bolt for a better grip and to enable more torque to be used for tightening. This was the birth of the combination wrench. A bit further down the line someone took the idea of the box wrench a bit further by elongating it into a cylinder with a square-drive hole at the opposite end, and the socket was invented. A drive bar with a mating square end could then be used to twist the socket enabling even greater torque to be applied to the bolt. Continuing this evolution, someone came up with the idea of creating a handle with a square-drive post that utilized a ratchet-and-pawl mechanism to drive a socket with a back-and-forth motion, thus eliminating the need to remove the drive head and reinsert it to advance the turning of the fastener. The ratchet was now on the scene. But wait – it gets even better! Yet another bright person looked at the ratchet and said, "Hmm - that could really be useful if you could incorporate it into a box wrench". And, lo and behold, Robert Owen, Jr. (1881-1956) invented the ratchet wrench and received a U.S. patent (number 1,072,980) on September 9, 1913. And more innovations continue to produce tools that are more efficient and comfortable to use for tightening and loosening fasteners. So now that you have a little background on wrenches, let's explore the various types that you're most likely to use in your garage. Open-Ended Wrench The open-ended wrench is the most common type of wrench used for mechanical work and it may have a single or double end. The head has its jaws offset by about 15 degrees from the run of the shaft, and this is so the spanner can be turned over to engage different flats of a nut when working in confined spaces. A variation of the straight open-ended wrench has one head set at anything up to 90 degrees to the shaft, which may have a slight curve. These wrenches are designed for working in confined places.
Irwin's automatic adjusting wrench is great for those jobs when you only have one hand free to use holding the tool.