What Are #10 Screws?

Number 10 Screw

• There are two defined standards for the number 10 screw size, one for fine threading and another for coarse threading. The International Organization for Standardization's defined measurements for a number 10 screw under the metric system have a major diameter of 4.5 millimeters and a pitch of 0.75 millimeters for coarse threads and a major diameter of 4.5 millimeters with a pitch of 0.5 millimeters for fine threads. The standard measurements of a number 10 screw under the imperial system are a major diameter of 0.19 inch with 24 turns per inch for a unified coarse screw and a major diameter of 1.9 inch with 32 turns per inch for a unified fine screw.

Screw Thread

• The screw thread is a major factor in determining screw size. Screw thread sizes, angles and distribution over the length of the screw are determined by the specifications recommended by the International Organization for Standardization (ISO). There are two sets of recommended specifications, one for metric measurements (ISO metric thread) and the other for imperial measurements (ISO inch thread). Both specifications state that screw threads should have a symmetrical V-form and be cut at an included angle of 60 degrees between the flanks.

Major Diameter

• The major diameter is the diameter of the screw threads and is usually the first number in a screw specification. If the screw has external threads, measure the major diameter over the crests. When measuring the major diameter of a screw, take the measurement from the least worn portion of the screw for the most accurate results, as the thread sizes decrease with wear.

Pitch

• The pitch is the measurement of the distance between crests on a thread. The measurement must be taken parallel to the axis of the screw. Pitch is measured in the number of turns per inch.