Drill Size Pipe Taps

Overview

Engineering reference data for Drill Size Pipe Taps 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

Symbol	Description	Unit
$x$	Input value	—
$y$	Output value	—
$k$	Conversion factor	—

British Standard Whitworth (BSW) Threads - Taps and Drill Sizes

Key Formula

The recommended drill size for creating a tapped hole with 75% thread depth can be calculated from the major diameter ($D$) and threads per inch (TPI). The formula for the 75% drill diameter ($d_{75}$) is: $d_{75} = D - \frac{0.9743}{TPI}$

Definitions

• TPI (Threads Per Inch): The number of complete thread turns per inch of fastener length.
• 75% Thread Engagement: A standard engineering practice where the depth of thread engagement is 75% of the theoretical full depth. This provides a strong connection while minimizing the risk of tap breakage.
• BSW (British Standard Whitworth): A screw thread standard, historically used in the UK and internationally, featuring a 55° thread angle. It was used as the basis for pipe thread standards like ISO 7-1.

Interactive Charts

References

• Original Source