Thread

Thread count is a measure of the coarseness or fineness of fabric. It is measured by counting the number of threads contained in one square inch of fabric, including both the length (warp) and width (weft) threads. It is used especially in regard to cotton linens such as bed sheets. And has been known to be used in the classification of towels. It is important to see that thread count is the number of threads counted along 2 sides (up and across), ADDED not multiplied as it is not an area measurement. Many sellers now use Metric figures of threads per 10 square centimeters instead of square inches. To convert: Metric tc divided by 1.25 = inch thread count.

A screw thread is a helical structure used to convert between rotational and linear movement or force. A screw thread may be thought of as an inclined plane wrapped around a cylinder or cone. The tightening of a fastener's screw thread is comparable to driving a wedge into a gap until it sticks fast through friction and slight plastic deformation.

The helix of a thread can twist in two possible directions, which is known as handedness. Most threads are oriented so that a bolt or nut, seen from above, is tightened (the item turned moves away from the viewer) by turning it in a clockwise direction, and loosened (the item moves towards the viewer) by turning counterclockwise. This is known as a right-handed (RH) thread, because it follows the right hand grip rule (often called, more ambiguously, "the right-hand rule"). Threads oriented in the opposite direction are known as left-handed (LH).

The cross-sectional shape of a thread is often called its form or threadform (also spelled thread form). It may be square, triangular, trapezoidal, or other shapes. The terms form and threadform sometimes refer to all design aspects taken together (cross-sectional shape, pitch, and diameters). Most triangular threadforms are based on an isosceles triangle. These are usually called V-threads or vee-threads because of the shape of the letter V. For 60° V-threads, the isosceles triangle is, more specifically, equilateral. For buttress threads, the triangle is scalene.

Lead and pitch are closely related concepts. The difference between them can cause confusion, because they are equivalent for most screws. Lead is the distance along the screw's axis that is covered by one complete rotation of the screw (360°). Pitch is the distance from the crest of one thread to the next. Because the vast majority of screw threadforms are single-start threadforms, their lead and pitch are the same. "Single-start" means that there is only one "ridge" wrapped around the cylinder of the screw's body. Each time that the screw's body rotates one turn (360°), it has advanced axially by the width of one ridge. "Double-start" means that there are two "ridges" wrapped around the cylinder of the screw's body. Each time that the screw's body rotates one turn (360°), it has advanced axially by the width of two ridges.