Question

The following data are given for calculating limits of dimension and tolerances for a hole: Tolerance unit

$i=0.45\left(D^{1/3}\right)+0.001D\text{(microns)}$.

The unit of D is mm. Diameter step is $18-30.$ If the fundamental deviation for hole H is zero and $\text{IT8=26i}$ , the maximum and minimum limits of dimension for a $25H_8$ hole (in mm) are

• A. $\text{25.033 and 25.00}$
• B. $\text{25.017 and 24.984}$
• C. $\text{25.00 and 24.967}$
• D. $\text{24.984 and 24.967}$

Answer 1

The correct option is A $\text{25.033 and 25.00}$

$\text{For diameter step 18-30 mm}$

$D=\sqrt{18\times 30}=23.23mm$

$\text{Tolerance unit (i)}=0.45D^{1/3}+0.001D$

$=1.284+0.02323$

$=1.307\mu m$

$IT8=26i=26\times 1.307$

$=33.98\approx 34\mu m$

$\text{Tolerance}=34\mu m=0.034mm$

$\text{Tolerance for}25H8=0.034mm$

$\text{Hole size}25H8={25}^{\begin{array}{c}+0.034\\ +0.00\end{array}}mm$