Question 4.3: Determine the fit types of shafts and holes in Table 4.3.
Determine the fit types of shafts and holes in Table 4.3.
Table 4.3 The shaft and hole dimensions (Example 4.3)
| Hole | Shaft | Case |
| 1.5000^{0.0}_{-0.005} | 1.5000^{0.0}_{-0.005} | 1 |
| 0.850^{0.0}_{-0.005} | 0.850^{+0.007}_{+0.002} | 2 |
| 0.575^{0.0}_{-0.004} | 0.575^{+0.003}_{-0.002} | 3 |
| 1.250^{+0.005}_{-0.0} | 1.250^{0.0}_{-0.003} | 4 |
Equation (4.10) is used to evaluate the maximum and minimum clearances, and the clearances are then used determine the fit types, and the results are shown in Table 4.4 (Fig. 4.34).
\left.\begin{matrix} Max. Clearance = LMC_{hole} – LMC_{shaft} \\\ Min. Clearance = MMC_{hole} – MMC_{shaft} \end{matrix} \right\} (4.10)
Table 4.4 Determining fit types by maximum and minimum clearances
| Fit type | Min clearance | Max clearance | MMC_{hole} | LMC_{hole} | MMC_{shaft} | LMC_{shaft} | Case |
| Clearance | 0.011 | 0.001 | 1.501 | 1.506 | 1.500 | 1.495 | 1 |
| Interference | -0.012 | -0.002 | 0.845 | 0.850 | 0.857 | 0.852 | 2 |
| Transition | -0.007 | 0.002 | 0.571 | 0.575 | 0.578 | 0.573 | 3 |
| Line | 0 | 0.005 | 1.250 | 1.255 | 1.250 | 1.247 | 4 |
In ASME standards, running or sliding (RC) fits are classified into 9 levels from 1 for the tightest to 9 for loosest. The locational fits are classified into (1) locational clearance (LC) fits with 11 levels, (2) locational transition (LT) fits with 6 levels, and (3) locational interference (LN) fits in 5 levels. The corresponding tolerances are standardized. Table 4.5 gives the excerpted tolerances for the fits of RC5 to RC9 and a basic size range of (0.0 in, 19.69 in). In the table, the first column is the range of basic size, the other columns are for standard limits for shaft and hole fits.
