Fastener Thread Engagement Ratio Design Calculator

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Engineering Metals and Materials | Strength of Materials

For equations and illustrative graphics see:
Minimum Thread Engagement Formula and Calculation ISO

This engineering calculator will determine the ISO Thread / Fastener Ratio and Length requirements for an engineering requirement.

All units shall be consistant and given in inches.

A screw is a mechanism that converts rotational motion to linear motion, and a torque (rotational force) to a linear force. It is one of the six classical simple machines. The most common form consists of a cylindrical shaft with helical grooves or ridges called threads around the outside. The screw passes through a hole in another object or medium, with threads on the inside of the hole that mesh with the screw's threads. When the shaft of the screw is rotated relative to the stationary threads, the screw moves along its axis relative to the medium surrounding it; for example rotating a wood screw forces it into wood. In screw mechanisms, either the screw shaft can rotate through a threaded hole in a stationary object, or a threaded collar such as a nut can rotate around a stationary screw shaft. Geometrically, a screw can be viewed as a narrow inclined plane wrapped around a cylinder.

ISO Thread Fastener Ratio - Engagement Length
Variables
Tensile Stress Screw / Fastener (ksi) =
Tensile Stress Internal Mating Thread (ksi) =
Calculated Min. Thread Engagement (Le) =
Results
Thread Engagement Ratio (J) =
If J > than 1 Minimum Thread Engagement Length (le) =