The wood screw
2008-08-20

A wood screw is proposed for use with a material made mainly of plastic waste and wood chips. The wood screw includes a shank which has leading threads extending from the tip of the tapered portion to an intermediate point of the straight portion and have a first lead angle and a first thread angle. Trailing threads extend from the intermediate point toward a head and have a second lead angle and a second thread angle. The first lead angle is greater than the second lead angle, and the first thread angle is smaller than the second thread angle. Wood Screws have either Phillips of slotted drive and in each drive type there are three head types; flat head, round head and oval head. The round head and flat head styles are most popular and there are more sizes to choose from these two head styles Although the principle of the screw is ancient, the wood screw - essentially a round nail with a threaded shaft and a slot in the head to aid its removal - seems to have developed in the mid 16th century when they were used in locks and clocks in particular. However, these early, hand-forged screws were expensive to make and they were not used for ordinary joinery work. Wood screw comprising a head for receiving a fastening tool and a shank extending from the head. The shank is provided at the tip thereof with a tip guide portion adapted to penetrate an article to be fastened while boring a hole into the article such as timber. The shank is provided at the head side thereof with a fastening screw portion having at least a single screw thread. A chips removing screw portion is disposed between the tip guide portion and the fastening screw portion. The chips removing screw portion has screw threads, the number of which is greater than that of the fastening screw portion. The screw thread lead angle of the chips removing screw portion is larger than that of the fastening screw portion. The length of a wood screw is measured from the tip of the point to the surface of the material into which the screw is driven, which is the head's widest part. So the length of a flat head wood screw is measured from the tip to the top of the head, but the length of a round head screw is measured from the tip to the bottom of the head. In the common wood screw the thread extends 2/3rds of the length of the screw. Some other types (such as sheet metal and dry wall screws) are threaded all the way to the head For many years American wood screws were made to two different standards, one a series that originated with the American Screw Co., and the other from the Asa I. Cook Co. In both series, sizes were indicated by gauge numbers, which went up to #30. (see historical table) The overall dimensions in the two series were the same, but the number of threads differed slightly. When an American Standard for wood screws was adopted, most of the diameters were within a few thousandths of an inch of the old dimensions, but the sizes extended only to #24. For the current body diameters of the various gauges, see the pilot holes table.