| ► As-cast HPDC tolerances of +/-0.1 to +/-0.3 mm are insufficient for sealing faces and precision bores — CNC achieves IT6 to IT8, down to +/-0.01 mm on specific features. |
| ► Standard CNC operations on die castings include facing, boring, drilling, tapping, milling and reaming — typically completed in 2 to 3 setups. |
| ► CNC machining cost for aluminium die cast parts in India ranges from INR 25 to INR 90 per part for standard operations at batch volumes. |
| ► ADC12 and A380 machine at cutting speeds of 200 to 400 m/min with carbide tooling — significantly faster than ferrous materials. |
| ► Post-casting CNC reduces assembly-fit issues by achieving flatness, bore diameter and positional tolerances that as-cast surfaces cannot hold. |
| ► Single-source suppliers offering casting and CNC eliminate interface risk and reduce total programme lead time by 20 to 35 percent. |
Introduction: Why As-Cast Surfaces Are Rarely Enough
Die cast aluminium parts leave the press as near-net-shape components with good general dimensions, but critical functional surfaces — sealing faces, bearing bores, threaded features and datum faces — require CNC machining to meet the tolerances that automotive and industrial assemblies demand. CNC machining aluminium die cast parts in Pune is a routine post-casting operation, yet its quality often determines whether the finished assembly seals, rotates or fastens as designed. This guide covers what CNC adds to a die cast component, what tolerances are achievable and how integrated sourcing reduces cost and risk.
| Parameter | Value |
| Achievable IT grade (CNC) | IT6 to IT8 on bores and critical faces |
| Bore diameter tolerance example | +/-0.015 mm to +/-0.025 mm at IT7 |
| Surface flatness achievable | 0.02 mm to 0.05 mm on faced surfaces |
| Typical CNC cost (standard ops) | INR 25 to INR 90 per part at volume |
| Cutting speed (ADC12 with carbide) | 200 to 400 m/min (dry or MQL) |
| Standard machining lead time | 5 to 10 working days after casting delivery |
| Metric | Data | Source |
| India CNC machining market size 2024 | USD 1.4 billion | IBEF Manufacturing 2024 |
| Precision machining CAGR India 2024-2029 | 9.3 percent | Industry estimate |
| Pune area CNC machining shops | 800+ registered units | CII Pune 2024 |
| Automotive precision machining share of India CNC | Approx. 42 percent | ACMA 2025 |
| Average machining stock removed on HPDC face | 0.3 to 0.8 mm per face | Industry estimate |
| Saving on machining time: HPDC vs sand casting | 25 to 40 percent less stock | Industry estimate |
| India auto-component CNC export value 2024-25 | USD 3.2 billion (est.) | ACMA 2025 |
Common CNC Operations on Die Cast Aluminium Parts
| Operation | Purpose | Tolerance Achievable |
| Face milling | Flat datum and sealing surfaces | Flatness 0.02 to 0.05 mm |
| Boring | Precision bearing and bush bores | IT6 to IT7, +/-0.01 to +/-0.02 mm |
| Drilling | Clearance and through holes | Position +/-0.05 mm from datum |
| Tapping | Threaded fastener holes | ISO metric thread to 6H tolerance |
| Reaming | Close-tolerance fit holes | H7 bore tolerance +0/+0.021 mm (25 mm) |
| Profile milling | Contoured mating faces | Profile tolerance 0.1 to 0.2 mm |
| Counterboring | Fastener head clearance | Diameter +/-0.1 mm typical |
Tolerances: What CNC Can Hold That As-Cast Cannot
As-cast High Pressure Die Casting tolerances fall within ISO 8062 CT6 to CT8, which is +/-0.1 mm to +/-0.3 mm on small features. This is adequate for non-functional surfaces but insufficient for bearing bores, sealing faces and locating features that mate to other precision components. A bearing bore that must accept an 80 mm outer-diameter bearing at H7 interference fit requires the bore to be held within +0/+0.030 mm — a tolerance that as-cast HPDC cannot achieve consistently. CNC boring achieves this routinely on aluminium, removing 0.3 to 0.5 mm from the cast bore to hit the final dimension.
Machining Aluminium: Speed, Tooling and Coolant
Aluminium silicon alloys machine at cutting speeds 3 to 5 times higher than mild steel, making CNC time per part significantly lower and cost proportionally cheaper. ADC12 with 12 percent silicon content is slightly abrasive, so carbide tooling with TiN or TiAlN coating is standard. Dry or minimum quantity lubrication (MQL) machining is the norm in Indian production shops. Flood coolant is used for bore finishing where thermal stability is critical to dimension control.
Integrated Casting and CNC: The Single-Source Advantage
When casting and CNC are sourced separately, quality accountability fragments. A dimensional non-conformance on a machined bore may stem from the casting being out of tolerance, the fixturing being poorly designed, or a programming error. With two suppliers, responsibility disputes and rework delays are common. Plasma manages casting and CNC at the same facility near Chakan, which eliminates the inter-supplier interface. The engineering team that designs the die also specifies the CNC datum scheme, ensuring both operations work as a coordinated system. This integration reduces total programme lead time by 20 to 35 percent compared to split-source programmes (Industry estimate).
CNC Cost Model for Pune Die Cast Parts
| Operation Type | Typical Cost per Part | Volume | Notes |
| Simple facing and 2 tapped holes | INR 25 to INR 40 | 1,000+ per batch | 1 setup, 3-axis VMC |
| Bore, face, drill, tap (4 operations) | INR 50 to INR 80 | 500+ per batch | 2 setups typical |
| Complex profile and 6+ features | INR 80 to INR 150 | 200+ per batch | 3+ setups, fixture amortised |
| CMM inspection per part | INR 15 to INR 35 | Per AQL plan | First-article and periodic |
| Fixture design and build (one-time) | INR 15,000 to INR 60,000 | Per part number | Amortised over programme |
FAQ: CNC Machining for Aluminium Die Cast Parts
Yes, Plasma can machine customer-supplied die castings from other sources. Integrated casting and machining programmes are preferred because they allow the datum scheme to be engineered correctly from the die design stage.
For parts already in casting production, CNC operations add 5 to 10 working days depending on operation complexity and scheduling. Integrated programmes typically plan both steps together, reducing the net additional time to 3 to 7 days.
Plasma’s machining centres achieve IT6 to IT8 on standard features. IT6 bores requiring +/-0.008 to +/-0.016 mm are achievable with fine boring heads and controlled thermal conditions. Contact the engineering team for specific tolerance feasibility on your drawing.
Standard documentation includes a dimensional inspection report with all critical feature measurements, surface roughness records for sealing faces, thread gauge records and material traceability from the casting stage. PPAP Level 3 documentation is available for automotive customers.
Plasma operates 3-axis and 4-axis CNC machining centres. For parts requiring simultaneous 5-axis machining, discuss requirements with the engineering team as external partner capacity may be coordinated for specific programmes.
Conclusion
CNC machining aluminium die cast parts in Pune transforms near-net-shape castings into assembly-ready precision components. The gap between as-cast tolerances and the IT6 to IT8 grades required for bearing bores, sealing faces and threaded features is bridged efficiently by post-casting CNC operations. Single-source suppliers integrating casting and CNC under one roof deliver faster programmes, cleaner quality accountability and lower total landed cost.
Submit your drawing and annual volume to us for a combined casting and CNC machining quotation from Plasma’s team.
Prasanna Kumar Tiwari
Plasma Aluminium Diecasting was established after analyzing the worldwide surge in manufacturing demand across diverse sectors — from automobiles to FMCG, Oil & Gas, and Pharma. To meet this growing need, we provide a comprehensive range of precision-engineered products and industrial solutions that streamline production and enhance efficiency. As a Leading Aluminium Die Casting Manufacturer in Pune, our commitment lies in delivering innovative, technology-driven, and cost-effective solutions tailored for modern industries.