Us And Metric Thread Sizes Comparing

Overview

Engineering reference data for Us And Metric Thread Sizes Comparing in miscellaneous.

Key Formulas

Unit Conversion

$y = x \cdot k$

Multiply by conversion factor.

Linear Interpolation

$y = y_1 + \frac{(x - x_1)(y_2 - y_1)}{x_2 - x_1}$

Estimate between two known points.

Percentage

$p = \frac{\text{part}}{\text{whole}} \times 100\%$

Part as fraction of whole.

Variables

Thread Size Comparison Standards

In the United States, the Unified Thread Standard (UTS) is prevalent, denoting thread size with a major diameter and threads per inch (e.g., 1/4"-20). The International Organization for Standardization (ISO) metric system uses a "M" designation followed by the major diameter and pitch in millimeters (e.g., M6x1).

Conversion Considerations

Direct dimensional equivalence between UTS and ISO metric threads is rare. Selection is based on matching the major diameter and pitch as closely as possible for the intended mechanical application. The formulas for thread geometry are defined within their respective standards.

Standard Thread Designations

• UTS: Size (Fractional inch or gauge number) - Threads Per Inch (TPI). Class of fit (e.g., 2A, 3A) may follow.
• ISO Metric: "M" + Nominal Diameter (mm) x Pitch (mm). Tolerance class (e.g., 6g, 6H) may follow.

Common Application Notes

Fastener selection depends on load requirements, material strength, and environmental factors. The thread designation system alone does not specify material strength grade (e.g., ASTM, ISO property classes).

References

• Original Source