As cast
For aluminum, controlled features typically reference ±0.05–±0.15 mm and general structural features ±0.10–±0.30 mm. Assess parting-line and moving-tool features separately.
Feature & inspection planning
Die Casting Tolerances & Quality Requirements
Define dimensional tolerances, flatness, coaxiality and surface texture for the applicable casting, sizing or machining stage.
Drawing & acceptance planning
Acceptance Requirements at a Glance
Identify the controlled features and their delivery state before agreeing tolerances, inspection methods and records.
- Feature & nominal size
- Characteristic number, nominal dimension and specified limits
- Material
- Exact alloy grade and required delivery condition
- Manufacturing stage
- As cast · After sizing · After machining · Before or after finishing
- Datum relationships
- Datum references, controlled surfaces and mating features
- Inspection method
- Measurement setup, access, sampling and evaluation conditions
- Release records
- Drawing revision, characteristic list and required inspection reports
Aluminum as-cast references: controlled features ±0.05–±0.15 mm; general structural features ±0.10–±0.30 mm. CNC critical features: ±0.02–±0.05 mm. Achieving ±0.02 mm requires a suitable fixture and process plan. Dimensions across the parting line require a separate assessment; confirm nominal size, feature location and inspection method.
Routine as-cast surface roughness: Ra 3.2–6.3 μm. Ra 0.8 μm applies only to designated local aluminum or zinc surfaces after CNC finish milling, finish turning or polishing. The process route, measurement location and evaluation conditions require individual review.
These are project-review references. The approved drawing and acceptance plan establish the requirements for the actual component.
Assign requirements to the operation
As Cast, Sized and Machined
After sizing
Identify the controlled area, support condition and local or overall geometric requirement after the agreed sizing operation.
After machining
Critical CNC features reference ±0.02–±0.05 mm; ±0.02 mm requires a suitable fixture and process plan. Identify the feature, datum, machining allowance and acceptance stage.
Manufacturing-stage review conditions
A useful tolerance statement identifies the alloy, nominal dimension, feature location and delivery condition. As-cast, sized and machined features are reviewed separately. Requirements across a parting line or moving mold element also need to be identified on the drawing.
The quotation review assesses each critical feature and identifies where secondary machining may be required. Confirm tolerances, inspection methods and any required trial validation in the technical agreement and inspection plan. Specify the order of precedence if project documents differ.
For aluminum as-cast features, typical controlled dimensions reference ±0.05–±0.15 mm; general structural features reference ±0.10–±0.30 mm. Critical CNC features reference ±0.02–±0.05 mm. Achieving ±0.02 mm requires a suitable fixture and process plan. Dimensions across the parting line or involving moving mold elements require a separate assessment.
Feature-specific requirements
Define the Feature and Measurement Location
- 1. Locating face: identify the drawing datum and support setup.
- 2. Critical hole: specify diameter, fit and datum relationships.
- 3. Controlled plane: identify the surface and geometric requirement.
- 4. Local wall: identify nominal thickness and measurement locations.
- 5. Surface texture area: specify parameter, unit and evaluation conditions.
| Requirement | What to specify | Inspection planning |
|---|---|---|
| Linear dimensions | Nominal size, limits, alloy and feature location | Select calibrated dimensional instruments or gauges appropriate to the tolerance |
| Critical holes and fits | Diameter, fit, datum relationships and delivery operation | Agree direct casting or secondary machining; select CMM, bore measurement or gauges as appropriate |
| Wall thickness | Nominal wall, allowed variation and measurement locations | Select a method that can access the relevant surfaces |
| As-cast flatness | Tolerance in mm over a defined surface | Agree the measured area, support condition, sampling and evaluation method |
| Flatness after sizing | Tolerance in mm, defined area and delivery state | Define local and overall requirements separately where needed |
| Coaxiality | Tolerance, datum axis, controlled feature and evaluation length | Prepare a feature-specific inspection plan |
| Surface texture | Ra or Rq, unit in μm, location and measurement conditions | Agree direction, filtering, evaluation conditions and surface state |
All numerical limits are subject to drawing and DFM review. A generic percentage for wall thickness, or a precision figure without its nominal dimension and operation, does not define the acceptance criteria for a new component.
Drawing references
Surface Texture and Standards
Identify the parameter, units, drawing standard and agreed edition in the acceptance plan. Preserve the same definitions in the inspection report.
Surface Texture Parameters
Routine as-cast surface roughness is Ra 3.2–6.3 μm. Ra 0.8 μm applies only to designated local aluminum or zinc surfaces after CNC finish milling, finish turning or polishing. Review the process route and measurement conditions for each specified surface; the requirement does not describe the whole as-cast part.
Ra and Rq are different roughness parameters. RMS terminology refers to the root-mean-square parameter; converting a length unit does not convert Rq into Ra. The drawing and inspection report must identify the same parameter, unit and measurement conditions. Mitutoyo roughness parameter guide
Drawing Standards
ISO 8062-3:2023 addresses general casting tolerances and machining allowances for indicated dimensions using ± tolerances. It does not apply to a 3D CAD model without indicated dimensions. Specify the applicable grade, dimension range and drawing reference when using this standard. ISO 1101:2017 defines geometrical specification symbols and interpretation rules. Use the drawing standard and edition agreed for the project. ISO 8062-3, ISO 1101
Project release requirements should identify the drawing revision, characteristic list, inspection stage and required records. Confirm any additional testing or customer approval requirements before production.
Acceptance Review Questions
Can I submit a drawing before selecting the inspection method?
Yes. Identify the critical features, nominal dimensions, tolerance requirements and delivery state. Engineering can clarify suitable measurement methods and any additional information needed.
What if the drawing and inspection specification differ?
Identify the conflicting requirements and document revisions. Agree the order of precedence and update the approved acceptance plan before release.
How should additional functional tests be requested?
Specify the function, test conditions, acceptance limits, inspection stage and required records. Include leakage, material or other tests where applicable so they can be reviewed with dimensional requirements.
Engineering resources
Plan Inspection and Release
Building a Practical Inspection Plan for Cast and Machined Parts
Translate drawing requirements and product risk into incoming checks, first-article inspection, in-process controls, final verification and shipment records.
Read engineering guide →Die Casting Defects: Causes, Prevention, and Inspection Strategy
A practical framework for classifying casting defects, investigating interacting causes, selecting controls, and matching inspection to functional risk.
Read engineering guide →Die Casting DFM Checklist Before Tooling Release
A drawing-based checklist for closing geometry, tooling, machining, finishing, inspection, and approval questions before die manufacture begins.
Read engineering guide →
Drawing & inspection review
Review Your Acceptance Requirements
Send the drawing and critical requirements so engineering can review the manufacturing and inspection plan together.
Include with your RFQ
- Drawing/CAD revision, alloy grade and quantities.
- Critical feature numbers, nominal dimensions and tolerance limits.
- Datum references, mating features and functional requirements.
- Acceptance stage: cast, sized, machined, before or after finishing.
- Drawing standard and edition; measurement and sampling requirements.
- Required reports, customer approvals and additional functional tests.