Question

A metric thread of pitch 2 mm and thread angle ${60}^{\circ }$ is inspected for its pitch diameter using the 3-wire method. The diameter of the best size wire in mm is

• A. $0.866$
• B. $2.000$
• C. $1.154$
• D. $1.000$

Answer 1

The correct option is C $1.154$

$\text{Pitch:}P=2mm$

$\text{Thread angle:}2\theta ={60}^{\circ }\text{for metric thread}$

$\Rightarrow \theta ={30}^{\circ }$

$\text{For best size wire}$

$d_w=\frac{P}{2}sec\theta$

$=\frac{2}{2}sec{30}^{\circ }=1.154mm$