Basic Quality Control Interview Questions (2026 Guide) Part 1 of 3

This article covers commonly asked basic quality interview questions for freshers, along with simple and clear answers to help you prepare confidently. Whether you are from mechanical, production, or any engineering background, these questions will give you a strong foundation to crack your first quality job interview.

What is Quality and Quality Policy of any organisation?

Quality: The part or product which has been manufactured inside the company, should be fit for use without failure, and as per customer requirement. Quality means “The degree of fineness of any product.”

Quality Policy: To provide complete customer satisfaction through timely delivery of quality product and services based on customer’s feedback with continuous improvement.

What is Quality Control and Quality Assurance?

Quality Control

Quality Control is a part of quality management system which emphasized on fulfilling quality requirement.

Quality Control is a part of quality management which focused that the manufactured part should be within the limit or as per control plan (customer requirement).

Quality Assurance

Quality Assurance is a part of quality management emphasizes on providing confidence that the quality requirement will be fullfilled.

What is the difference between Quality Control and Quality Assurance?

Quality Assurance	Quality Control
Prevent Defects	Identify, Detect Defects
Therefore, Proactive Approach	Reactive Approach
Cross Fxn Team(CFT): Quality, Prod., Maintenance, Tool room all give input	Dedicated Quality Department Team Works in Quality Control
We do periodically Statistical Process Control, Product & Product Audit	Eliminate the defects by QC Tools- Patrol Inspection, Acceptance Sampling

What is Nominal and Tolerance Size?

Nominal Size	Tolerance
Nominal size is the standard or basic size given to a part.	Tolerance is the limit or allowed variation in Nominal Size.
It is the target size used for design	It defines how much actual size can increase or decrease
It is usually a rounded or convenient number	Because perfect manufacturing is not possible
A shaft is designed as 50 mm = Nominal size	Tolerance = Maximum size – Minimum size

There are 2 Types of Tolerances

Unilateral Tolerance

Variation in one direction only
Example: 50 mm +0.02 / 0

Bilateral Tolerance

Variation in both directions
Example: 50 mm ±0.02

Difference (Easy Table)

Feature	Nominal Size	Tolerance
Meaning	Basic size	Allowed variation
Purpose	Design reference	Manufacturing limit
Example	50 mm	±0.02 mm

What are Jigs and Fixtures?

Jigs

Jig is a tool that guides the cutting tool as well as holds the workpiece.

👉 It tells the tool where and how to cut/drill
A drilling jig used to make holes in the exact same position every time
It has bushings that guide the drill bit
➡️ Guides the tool + holds the workpiece

Fixtures

Fixture is a tool that only holds and supports the workpiece in the correct position.

👉 It does NOT guide the tool
A milling fixture that holds a part firmly while machining
A welding fixture that keeps parts aligned
➡️ Holds the workpiece only

Difference between Jigs & Fixtures

Jigs	Fixtures
Hold & Position the work-piece and guide the cutting tool.	Hold & Position the work-piece but not guide the cutting tool.
Not fixed on work table.	Fixed on work table.
Use for lighter work. e.g. Drilling, Boring, Reaming, Tapping.	Use for heavy work e.g. Milling, Grinding, Shaping, Slotting.

What is the difference between First Angle Projection and Third Angle Projection?

First Angle Projection	Third Angle Projection
Object imagine in 1st Quadrant	Object imagine in 3rd Quadrant
Top view comes below the front view	Top view comes above the front view
Right side view drawn to the left side of elevation	Right side view drawn to the right side of elevation

Types of Inspection Method?

There are 2 types of inspection methods.

Attribute Method

Attribute Method: Measurements through gauges which define OK or NOT OK. Examples: Plain Plug Gauges, Snap Gauges.

Variable Method

Variable Method: measurement by instruments which define measurement values. Examples: Vernier Caliper, Micrometer, Bevel Protector.

What is Least Count?

It is a minimum value which an instrument can measure.

📏 Ruler

Smallest division = 1 mm
👉 Least count = 1 mm

🔧 Vernier Caliper

Can measure up to 0.01 cm (or 0.1 mm)
👉 Least count = 0.01 cm

⚙️ Micrometer Screw Gauge

Very precise
👉 Least count = 0.001 cm

Types of Errors in Any Instrument?

Positive Error and Negative Error describe whether your measured value is higher or lower than the true value.

Positive Error	Negative Error
We will minus from Actual Reading	We will add in Actual Reading
Error value is positive (+)	Error value is negative (−)

Positive Error

True value = 50 mm
Measured value = 52 mm
Error = 52 − 50 = +2 mm
Instrument is over-reading

Negative Error

True value = 50 mm
Measured value = 48 mm
Error = 48 − 50 = −2 mm
👉 Instrument is under-reading

What is GD&T?

GD&T (Geometric Dimensioning and Tolerancing) is a symbolic language used in engineering drawings to control the shape, position, orientation, and accuracy of a part.

Simple Interview Definition

“GD&T is used to define the allowable variation in a component so parts can fit and function properly during assembly.”

Practical Example:

A shaft may have the correct diameter but still be slightly bent.
GD&T helps control such issues so the shaft rotates smoothly inside a bearing.

👉Click Here for Complete Guide on GD&T

Slip Gauges, Feeler Gauges, Spirit Level

Slip Gauges

Slip gauges (also called gauge blocks or Johansson gauges) are precision measuring blocks used to obtain very accurate dimensions.

Different blocks can be joined together (“wrung”) to create an exact required size.

They are made of hardness steel, ceramic, or carbide.
Precise measurement of length
To check the accuracy or to calibrate Vernier Caliper, Micrometer, Slip gauges etc.
1.001 mm to 90 mm of size variation.
High degree of surface finish, flatness, and accuracy.
Wringing action for joining slip gauges and sliding action to make it separate.
Measurement of angle by using slip gauges with the help of SINE BAR.
Used in metrology labs and industries

Feeler Gauges

Feeler gauges are thin metal strips, which are used to measure small clearance or gap between 2 parts.

Examples:

Spark plug gap
Valve clearance
Piston cylinder clearance
Quality Control: Ensuring proper fitting and alignment

If two metal parts should have a gap of 0.20 mm, a 0.20 mm feeler gauge blade is inserted to check whether the gap is correct.

There blade ranges from 0.02 mm to 1.00 mm (metric type).

Spirit Level

A spirit level is a measuring tool used to check whether a surface is perfectly horizontal (level) or vertical.

It contains a small tube filled with liquid and an air bubble inside.
When the bubble stays in the center between the marked lines, the surface is level.

The liquid is low viscous or can be alcohol.

Uses:

Construction work
Carpentry
Machine installation
Furniture alignment
Wall mounting

Difference Between Drilling, Boring and Reaming.

Drilling	Boring	Reaming
To originate a hole	To enlarge the dia (Ø) of existing hole	To finish hole’s surface & to improve tolerance.
Cutting Tool: Drill Bit	Boring Bar	Reamer
Drill is double point cutting tool	It is a single point cutting tool	It is a multi point cutting tool
Material Removal Rate (M.R.R.) is higher	MRR is lower as compared to Drilling	MRR is very less. However, it’s not an issue
Surface quality of hole is poor	Here it is better than Drilling	Highly surface finish
Drill can increase the length of the hole but not the dia Ø	Boring can increase the Ø of the hole but not the length	Reaming can neither increase the Ø nor the length
First phase of hole	Pre-drilled hole is mandatory	Similar to boring, hole must required

What will you do if you find a defect in production?

Stop the process
Inform supervisor
Identify root cause
Take corrective action
Prevent recurrence