Day 11 Machining – ECET 2026 Mechanical

Why this topic is important for ECET?

Machining is a core manufacturing process in diploma and competitive exams like ECET 2026. Almost every year, questions come from lathe operations, cutting parameters, tool life, and machining economics. Understanding machining will not only help you score directly but also give confidence in industrial applications like automotive, workshop practice, and production jobs.

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📘 Concept Notes

🔹 What is Machining?

Machining is a material removal process where unwanted material (chip) is cut off from a workpiece using a cutting tool to get the desired size, shape, and finish.
Examples: Turning, Drilling, Milling, Shaping, Grinding.

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🔹 Types of Machining Processes

1. Conventional Machining
   • Uses cutting tools with defined geometry.
   • Examples:
     • Turning (Lathe)
     • Drilling (Drill press)
     • Milling (Horizontal/Vertical mills)
     • Shaping & Slotting
     • Grinding
2. Non-Conventional (Advanced) Machining
   • Uses non-traditional energy sources.
   • Examples:
     • EDM (Electric Discharge Machining)
     • ECM (Electrochemical Machining)
     • Laser Beam Machining (LBM)
     • Water Jet Machining

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🔹 Important Elements in Machining

1. Cutting Parameters
   • Cutting speed (V)
   • Feed (f)
   • Depth of cut (d)
2. Cutting Tools
   • Tool geometry → rake angle, clearance angle.
   • Tool materials → HSS, Carbide, Ceramics, Diamond.
3. Machining Economics
   • Tool life, machining cost, production rate.

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🔹 Tool Life (Taylor’s Tool Life Equation)

where

• VVV = Cutting speed (m/min)
• TTT = Tool life (min)
• nnn = Tool life exponent (depends on tool-work combination)
• CCC = Constant

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🔹 Machining Examples

• Turning: Removing material by rotating workpiece on a lathe.
• Drilling: Making holes using a drill bit.
• Milling: Removing material with a rotating cutter.
• Grinding: Achieving fine finish and close tolerances.

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⚙️ Formulas

1. Cutting Speed (Lathe):
   
   where DDD = Diameter (mm), NNN = RPM
2. Material Removal Rate (MRR):
   
   where VcV_cVc​ = Cutting speed, fff = feed, ddd = depth of cut
3. Taylor’s Tool Life Equation:

Machining Time (Turning):

where LLL = Length of cut, fff = feed per revolution

Power Consumption in Machining:

where FcF_cFc​ = Cutting force, VVV = Cutting speed

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🔟 10 MCQs

Q1. In a lathe machine, cutting speed depends on:
a) Workpiece diameter & spindle speed
b) Depth of cut & feed
c) Tool material only
d) Machine type

Q2. The formula for MRR in turning is:
a) πDfd\pi D f dπDfd
b) VcfdV_c f dVc​fd
c) fdf dfd
d) πNfd\pi N f dπNfd

Q3. According to Taylor’s equation, if tool life exponent nnn = 0.25, doubling tool life requires cutting speed reduction by:
a) 25%
b) 50%
c) 16%
d) 29%

Q4. Grinding is mainly used for:
a) Material removal at high rate
b) Producing rough surface finish
c) Accurate size and fine finish
d) Plastic machining

Q5. Which of the following is a non-conventional machining process?
a) Turning
b) EDM
c) Milling
d) Drilling

Q6. In drilling, the cutting speed is maximum at:
a) Drill center
b) Drill periphery
c) Mid-radius
d) Uniform across drill

Q7. If a workpiece of diameter 100 mm is rotated at 500 rpm, the cutting speed is:
a) 157 m/min
b) 314 m/min
c) 100 m/min
d) 62.8 m/min

Q8. Tool wear is minimum in:
a) HSS tools
b) Carbide tools
c) Ceramic tools
d) Diamond tools

Q9. Machining time decreases when:
a) Feed decreases
b) RPM decreases
c) Feed increases
d) Cutting speed decreases

Q10. Specific energy requirement is least in:
a) Grinding
b) Turning
c) Milling
d) EDM

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✅ Answer Key

Q	Ans
1	a
2	b
3	d
4	c
5	b
6	b
7	a
8	d
9	c
10	b

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🧠 Explanations

• Q1: Cutting speed = πDN/1000 → depends on workpiece diameter & spindle speed → (a).
• Q2: MRR in turning = VcfdV_c f dVc​fd → (b).
• Q3: From Taylor’s equation, doubling tool life reduces speed by (2^-n) = 2^-0.25 ≈ 0.84 → 16% reduction → (d).
• Q4: Grinding → accurate size & fine surface finish → (c).
• Q5: EDM is a non-conventional process using sparks → (b).
• Q6: Cutting speed = πDN → maximum at periphery → (b).
• Q7: V=πDN/1000=3.14×100×500/1000=157 m/minV = \pi DN/1000 = 3.14 \times 100 \times 500 / 1000 = 157 \, m/minV=πDN/1000=3.14×100×500/1000=157m/min → (a).
• Q8: Diamond tools have highest hardness & lowest wear → (d).
• Q9: Machining time T=L/(fN)T = L/(fN)T=L/(fN), increasing feed reduces machining time → (c).
• Q10: Turning has least specific energy (compared to grinding, milling, EDM) → (b).

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🎯 Motivation / Why Practice Matters

Machining questions in ECET 2026 test both theoretical understanding (tool life, MRR, parameters) and numerical accuracy.
👉 Practicing regularly improves speed in formula-based calculations, accuracy in conceptual choices, and builds a competitive edge over others who just memorize definitions.
ECET rewards fast solvers – that’s only possible by practice.

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📲 CTA

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