Material choice affects strength, corrosion resistance, weight – and how much your part costs to machine. Here is a practical comparison of the materials most often used for CNC turned and VMC machined parts in India.
What to consider when choosing a material
- Strength and hardness – what loads, wear or impact will the part see?
- Corrosion resistance – will it face moisture, chemicals or outdoor use?
- Weight – does the part need to be light?
- Machinability – how easily and quickly it can be cut, which drives cost.
- Heat treatment or plating – will the part be hardened, plated or coated?
- Availability – common grades and bar sizes are faster and cheaper to source.
Carbon and alloy steels
Mild steel (MS)
Low-carbon steel is economical, easy to machine and weld, and widely available. It suits brackets, plates, spacers and general parts that do not need high strength. It rusts, so it is usually painted, blackened or plated.
EN8 (080M40)
A medium-carbon steel with better strength than mild steel. Very common for shafts, pins, studs, gears and general engineering parts. It can be surface hardened where wear resistance is needed.
EN19 (42CrMo4) and EN24
Alloy steels with high strength and toughness, used for heavily loaded shafts, gears and high-stress components. They are often supplied hardened and tempered, which makes machining slower than EN8.
Stainless steels
SS304
The most common stainless steel. Good corrosion resistance for general use, food equipment and outdoor parts. It work-hardens, so it needs sharp tools and correct cutting parameters.
SS316
Contains molybdenum for better resistance to chlorides and chemicals – preferred for marine, chemical, pharma and some food applications. It costs more and is slightly harder to machine than 304.
Aluminium and brass
Aluminium (6061 / 6082 and similar)
About one-third the weight of steel, corrosion resistant and very quick to machine. Ideal for housings, plates, fixtures and lightweight VMC parts. It can be anodised for extra protection and appearance.
Brass (free-cutting)
One of the easiest metals to machine, with excellent surface finish and good corrosion resistance. Widely used for fittings, connectors, valve parts and electrical components on CNC lathes.
Engineering plastics
Plastics such as acetal (POM/Delrin) and nylon are machined for bushes, guides, insulators and low-friction parts. They are light and self-lubricating but less stiff than metals, and dimensions can change with temperature and moisture – so allow suitable tolerances.
Quick comparison table
| Material | Strength | Corrosion resistance | Machinability | Typical parts |
|---|---|---|---|---|
| Mild steel | Medium | Low | Good | Brackets, plates, spacers |
| EN8 | Medium–high | Low | Good | Shafts, pins, studs |
| EN19 / EN24 | High | Low | Moderate | Loaded shafts, gears |
| SS304 | Medium | High | Moderate | Food, general corrosion-resistant parts |
| SS316 | Medium | Very high | Moderate | Marine, chemical, pharma parts |
| Aluminium | Medium (light) | Good | Excellent | Housings, plates, fixtures |
| Brass | Medium | Good | Excellent | Fittings, connectors, valves |
| POM / Nylon | Low | Excellent | Good | Bushes, guides, insulators |
This table is a general guide. Exact properties depend on the specific grade, condition and heat treatment.
Tips to control material cost
- Specify the exact grade on the drawing – “MS” or “SS” alone is not enough.
- Use standard bar and plate sizes where possible to reduce waste.
- Choose the lowest grade that meets the function – over-specifying adds cost.
- Ask your supplier about a more machinable alternative if the function allows.
Not sure which material fits your part? Send us the drawing and application and we will suggest suitable options for CNC turning or VMC machining. You may also find our guide on CNC vs VMC machining useful.
Frequently Asked Questions
Which metal is easiest to CNC machine?
Free-cutting brass and aluminium alloys are among the easiest metals to machine. They cut quickly with good surface finish and low tool wear, which keeps machining cost down.
What is the difference between EN8 and EN19?
EN8 is a medium-carbon steel used for general shafts and parts. EN19 is a chromium-molybdenum alloy steel with higher strength and toughness, used for more heavily loaded parts and often supplied hardened and tempered.
Should I choose SS304 or SS316?
SS304 suits most general corrosion-resistant parts. SS316 contains molybdenum and resists chlorides better, so it is preferred for marine, chemical and some food and pharma applications. SS316 usually costs more.
CNC and VMC machining specialists in Metoda GIDC, Rajkot. Questions about your part? Send us your drawing.
