The Top Chinese Customized Parts Partner
Tolerance Standards
Design with Confidence, Quote with Accuracy, Deliver with Certainty. Core Design Tolerance design is the core link balancing product assembly accuracy, manufacturing difficulty and production cost.
Commonly Standards
Universal Standard: ASME Y14.5 is applicable to all processes for critical geometric dimensioning and tolerancing.
Common Drawing Callout: ISO 2768-mK (Most general mechanical parts),
Our company produces according to 2D drawing’s tolerances. If no tolerances are indicated, we will produce in accordance with ISO2678-mK.
Manufacturing Process | Core Tolerance Standard | Usage Description |
CNC Machining | ISO 2768， ISO 286 ，ASME Y14.5 | ISO 2768: General dimension tolerance for non-marked features ISO 286: Hole & shaft mating fits, ASME Y14.5: GD&T geometric tolerance control |
Mold Making | ISO 20457，ISO2768/286、ASME Y14.5 | ISO 20457: Plastic injection molded part tolerance (shrinkage compensation) ISO 2768/286: Mold base, guide pin & bushing tolerance ASME Y14.5: Cavity, core and shut-off surface GD&T control |
Stamping / Sheet Metal | ISO 2768、ASME Y14.5 | ISO 2768: Default general tolerance for blanking and bending ASME Y14.5: Precision position & profile geometric tolerance |
Die Casting | ISO 8062-3、NADCA 4-2 | ISO 8062-3: International standard for as-cast dimension toleranceNADCA 4-2: North American standard for Al/Zn/Mg die casting grades |
Rapid Prototyping | ISO/ASTM 52927、ISO 2768 (Reference) | ISO/ASTM 52927: AM industry dimensional acceptance standardISO 2768: Auxiliary baseline for drawing specification |
Tolerance Details for Different Manufacturing Processes
CNC Machining Tolerance Standard (Metal & Plastic)
Process Features: High precision, suitable for prototype verification and small-batch precision parts; stable dimensional accuracy but high cost for ultra-precision tolerance.
DFM Reminder: Avoid full-size tight tolerance marking. For single-sided matching gaps and auxiliary mounting dimensions, free tolerance is prioritized to reduce processing difficulty.
Special Note: Plastic CNC parts have poor rigidity; the overall tolerance is loosened by 0.02–0.05mm compared with metal parts to avoid deformation after processing.
|
Dimension Range (mm) |
General Free Tolerance (mm) |
Precision Matching Tolerance (mm) |
Appearance Flatness / Verticality (mm) |
|
0–10 |
±0.08 |
±0.03 |
0.05 |
|
10–50 |
±0.12 |
±0.05 |
0.08 |
|
50–100 |
±0.15 |
±0.08 |
0.12 |
|
100–200 |
±0.20 |
±0.10 |
0.15 |
Plastic Injection Molding Tolerance Standards
Process Features: Suitable for mass production; affected by mold shrinkage, ejection stress and cooling deformation, tolerance accuracy is lower than CNC.
DFM Reminder: Appearance surface dimensions and large-span outline dimensions strictly prohibit ultra-tight tolerances; assembly clearance tolerance is reserved based on shrinkage rate.
Special Note: Nylon, POM and other high-shrinkage materials need to loosen the overall tolerance by 20%–30% to prevent shrinkage deformation and assembly jamming.
Dimension Range (mm) | Free Tolerance (Mass Production) | Key Assembly Tolerance | Shaft / Hole Matching Tolerance |
0–20 | ±0.10 | ±0.05 | +0.05 / -0.05 |
20–60 | ±0.15 | ±0.08 | +0.08 / -0.08 |
60–150 | ±0.20 | ±0.12 | +0.10 / -0.10 |
150–300 | ±0.30 | ±0.15 | +0.15 / -0.15 |
Die Casting Tolerance Standard (Aluminum Alloy / Zinc Alloy)
Process Features: Fast forming speed, large mold shrinkage and thermal deformation; high-precision matching surfaces must be reserved for CNC finishing allowance.
DFM Reminder: As-cast blank dimensions only retain free tolerance; all precision holes and fitting surfaces rely on secondary finishing to ensure accuracy.
Special Note: The reserved finishing allowance for die-casting precision surfaces is 0.2–0.5mm, which can completely eliminate blank deformation tolerance errors.
Dimension Range (mm) | As-Cast Blank Tolerance | Post-Finishing Precision Tolerance | Flatness Deformation Tolerance |
0–30 | ±0.15 | ±0.05 | 0.10 |
30–80 | ±0.20 | ±0.08 | 0.15 |
80–150 | ±0.25 | ±0.10 | 0.20 |
150–250 | ±0.35 | ±0.12 | 0.25 |
Metal Stamping & Sheet Metal Tolerance Standard
Process Features: High batch consistency, stable punching size, large bending rebound error; bending dimension tolerance is looser than punching.
DFM Reminder: Hole spacing and outline punching dimensions are precise; bending height and angle need to reserve rebound compensation tolerance.
Special Note: Thin sheets (≤0.5mm) have obvious rebound, and the bending tolerance is appropriately loosened by 0.05–0.1mm.
Dimension Type | 0–50mm | 50–150mm | 150–300mm |
Punching / Hole Position / Outline | ±0.08 | ±0.12 | ±0.18 |
Bending Size & Height | ±0.15 | ±0.20 | ±0.30 |
Bending Angle Tolerance | ±0.5° | ±0.8° | ±1.0° |
Aluminum Extrusion Tolerance Standard
Process Features: Suitable for long strip profile parts; stable section size, large overall length error and straightness deviation.
DFM Reminder: Section matching dimensions are precise; overall length and assembly positioning need to avoid relying on single extrusion accuracy, and secondary cutting/finishing is adopted for key positions.
Tolerance Item | Standard Tolerance | Precision Level Tolerance |
Section Wall Thickness | ±0.10mm | ±0.05mm |
Section Outline Size | ±0.15mm | ±0.08mm |
Overall Length Cutting | ±0.50mm | ±0.20mm |
Straightness (per 100mm) | 0.10mm | 0.05mm |
Laser Cutting Tolerance Standard
Process Features: Fast forming, suitable for sheet metal non-standard profiling; affected by thermal cutting, the edge precision is lower than stamping and wire cutting.
DFM Reminder: Not applicable for precision assembly matching; only used for outline blanking and non-cosmetic structural parts.
Dimension Range | Outline Size Tolerance | Flatness Tolerance |
0–100mm | ±0.15mm | 0.10mm |
100–300mm | ±0.25mm | 0.15mm |
300–500mm | ±0.35mm | 0.20mm |
3D Printing Tolerance Standard (Resin / SLM / FDM)
Process Features: Rapid prototyping, suitable for complex special-shaped structures; large layer line error and shrinkage deformation, not suitable for high-precision matching.
DFM Reminder: Used for prototype verification only; mass production matching structures cannot rely on 3D printing tolerance.
Process Type | 0–50mm | 50–100mm | Surface Feature |
Resin SLA | ±0.10mm | ±0.15mm | Smooth, fine layer lines |
Metal SLM | ±0.15mm | ±0.20mm | Powder sticking, needs finishing |
FDM Plastic | ±0.20mm | ±0.30mm | Obvious layer lines, low precision |
Vacuum Casting Tolerance Standard
Process Features: Medium and small batch replica molding, low mold cost; affected by silica gel mold deformation, the tolerance is between injection molding and 3D printing.
DFM Reminder: Suitable for small-batch trial production appearance parts; key assembly dimensions need to loosen tolerance appropriately.
Dimension Range | General Free Tolerance | Key Assembly Tolerance |
0–50mm | ±0.15mm | ±0.08mm |
50–150mm | ±0.20mm | ±0.12mm |
150–250mm | ±0.30mm | ±0.18mm |
Would you like to start a project with us?
Universal Tolerance Design Rules & DFM Summary
Hierarchical Tolerance Marking Rule
Classify dimensions into appearance dimensions, functional non-matching dimensions & key matching dimensions. Only key matching dimensions are marked with precise tolerances, the rest adopt process free tolerances by default to balance quality and cost.
Tolerance Accumulation Avoidance Rule
Multi-part assembly stack easily causes tolerance superposition. Optimize positioning structure, adopt unified reference benchmark, and reserve reasonable assembly gaps to offset cumulative errors.
Process-Matching Tolerance Rule
Strictly match the tolerance range according to the actual manufacturing process. Do not mark CNC-level precision tolerances for injection molding, stamping and other batch processes to avoid unmanufacturable design and batch scrap.
Deformation Pre-Compensation Rule
For easily deformed structures (thin-walled injection parts, long aluminum profiles, bent sheet metals), actively loosen tolerance or add structural reinforcement at the design stage to eliminate deformation-induced dimensional failure.
