1. Superior Machinability:
   • En1a: Excellent machinability due to high sulphur content (0.20-0.30%)
   • Mild Steel: Lower machinability due to lower sulphur content (typically <0.05%)
   • Benefit: En1a allows for higher cutting speeds, longer tool life, and better surface finish.
2. Chip Formation:
   • En1a: Produces short, brittle chips that break easily
   • Mild Steel: Tends to form long, stringy chips
   • Benefit: En1a’s chip formation improves swarf clearance and reduces the risk of chip entanglement.
3. Production Efficiency:
   • En1a: Higher production rates due to faster machining speeds
   • Mild Steel: Lower production rates
   • Benefit: En1a can significantly reduce production time and costs in high-volume manufacturing.
4. Tool Wear:
   • En1a: Reduced tool wear due to easier cutting
   • Mild Steel: Higher tool wear rates.
   • Benefit: En1a leads to lower tooling costs and less frequent tool changes.
5. Surface Finish:
   • En1a: Generally provides a better surface finish in machining operations
   • Mild Steel: May require additional finishing operations.
   • Benefit: En1a can reduce or eliminate secondary finishing processes.
6. Dimensional Accuracy:
   • En1a: Easier to achieve tight tolerances due to better machinability
   • Mild Steel: May require more careful machining to achieve tight tolerances.
   • Benefit: En1a allows for more precise parts with less effort.
7. Power Consumption:
   • En1a: Lower power consumption during machining due to easier cutting
   • Mild Steel: Higher power consumption
   • Benefit: En1a can lead to energy savings in large-scale production.
8. Suitability for Automatic Machinery:
   • En1a: Ideal for use in automatic lathes and screw machines
   • Mild Steel: Less suitable for high-speed automatic machinery
   • Benefit: En1a is better suited for automated, high-volume production.
9. Cost-effectiveness in Machining:
   • En1a: Higher material cost offset by significant machining cost savings
   • Mild Steel: Lower material cost but higher machining costs
   • Benefit: En1a often provides better overall cost-effectiveness in machined parts.
10. Consistency:
    • En1a: More consistent machining characteristics due to controlled composition
    • Mild Steel: May have more variability in machining properties
    • Benefit: En1a provides more predictable and repeatable machining results.

It’s important to note that while En1a offers these machining advantages, mild steel may be preferred in applications requiring:

• Higher strength or toughness
• Better weldability for structural applications
• Lower material costs where machinability is not a primary concern
• Better corrosion resistance (though both require protection in corrosive environments)

In conclusion, En1a free cutting steel is the superior choice for high-volume production of machined parts where ease of machining is prioritized over strength and weldability. The decision between En1a and mild steel should be based on the specific requirements of the application, balancing machinability against other mechanical and economic factors.