SSOSS Cast Pte Ltd

What Is Machining Allowance and Why It Matters In Die Casting?

Quick Answer: Machining allowance in die casting is the extra material deliberately added to the casting — on surfaces that will later be CNC machined — so the cutter has clean stock to remove. For aluminium die casting (ADC12/A380), typical allowances run 0.5–1.5mm per surface. For zinc (Zamak 3/5), tighter as-cast tolerances mean allowances can be as low as 0.3–0.5mm.

How Much Allowance: Rules By Feature and Material?

The right allowance depends on two variables: what the feature does and what alloy you are casting. Here is what we apply in production. ADC12 / A380 Aluminium Die Casting Aluminium’s higher shrinkage rate, larger typical part size, and cold-chamber process (which introduces more shot variability) all push allowances higher than zinc.

How to Specify Machining Allowance on Your Drawing?

Getting the allowance right is only useful if it is communicated clearly between the design engineer, the die caster, and the machinist. Here is how to do it. On the casting drawing (the die cast part print): Mark every surface that will be machined with the ISO machining required symbol (a circle with a horizontal line — the “tick” mark per ISO 1302).

What Is The Real Cost Crossover Point?

For most small to medium parts, 3D printing becomes more expensive than die casting or injection moulding once you exceed 200 to 500 units. Tooling for aluminium die casting starts at US$5,000 to $15,000. Injection mould tooling ranges from US$5,000 to $50,000. The crossover point depends on part complexity, material, and annual volume requirements. Here is how the math works.

Volume Thresholds: How Many Units Before You Should Switch?

The decision is not always clean. Here is a practical framework by volume range. Under 100 units: Stay with 3D printing. Tooling cost cannot be recovered at this volume. Fast iteration and zero upfront spend are your advantage. Use this phase to lock your design. 100 to 500 units: Grey zone.