Manufacturing Practices (BT-106) - Important Questions

Explain the system of fits and tolerances. Describe the difference between clearance fit, interference fit and transition fit. Illustrate using representative hole and shaft tolerance positions.

Describe the construction, working and use of limit gauges (plug gauge, ring gauge and snap gauge). Explain how Go and No-Go gauges are designed relative to the tolerance limits.

Explain the principles of Geometric Dimensioning and Tolerancing (GD&T). Define datum, feature control frame and describe positional tolerance, concentricity and perpendicularity symbols with examples of how they are applied on engineering drawings.

Define common surface roughness parameters such as $R_a$ and $R_z$. Describe the working principle of a contact profilometer and outline the procedure to measure $R_a$ on a turned component.

Describe the construction and working principle of a Coordinate Measuring Machine (CMM). Explain different probe types and the typical inspection tasks performed using a CMM.

Explain the construction and interpretation of $\bar{X}$ and $R$ control charts. Derive the expressions for control limits of the $\bar{X}$ chart in terms of subgroup averages and ranges. State the formulae for upper and lower control limits.

Define process capability indices $C_p$ and $C_{pk}$. Give the formulae for both indices and explain how they are interpreted for an industrial process.

Include the standard formulae: $$C_p = \frac{\left(\text{USL} - \text{LSL}\right)}{6\sigma}$$

and

$$C_{pk} = \min\left(\frac{\left(\text{USL} - \mu\right)}{3\sigma},\; \frac{\left(\mu - \text{LSL}\right)}{3\sigma}\right).$$

Explain single sampling plans for acceptance sampling. Define Operating Characteristic (OC) curve and discuss how it is used to select a sampling plan.

What is calibration and traceability? Describe the calibration procedure for a Vernier caliper and list typical uncertainty sources to be considered.

Discuss measurement system analysis with emphasis on Repeatability and Reproducibility (Gage R&R). Explain the steps of conducting a Gage R&R study and how the results are interpreted for acceptability.

Compare the principles, typical applications and limitations of the following non-destructive testing (NDT) methods: ultrasonic testing, radiographic testing, dye penetrant testing and magnetic particle testing.

Explain the standard surface finish symbols used on engineering drawings. Show how to specify a required surface roughness and lay direction on a component drawing.