What is the Tolerance of Castings?

Casting tolerance refers to the acceptable limit of dimensional variation in metal castings after production. For parts requiring high precision, stricter tolerances must be applied to ensure accuracy.

Standard Parameters of Casting Tolerance

Size		Tolerance(mm)
>	≤	CT3	CT4	CT5	CT6	CT7	CT8
	10	0.18	0.2	0.36	0.52	0.74	1
10	16	0.2	0.28	0.38	0.54	0.78	1.1
16	25	0.22	0.3	0.42	0.58	0.82	1.2
25	40	0.24	0.32	0.46	0.64	0.9	13
40	63	0.26	0.36	0.5	0.7	1	1.4
63	100	0.28	0.4	0.56	0.78	1.1	1.6
100	160	0.3	0.44	0.62	0.88	12	1.8
160	250	0.34	0.5	0.7	1	1.4	2
250	400	0.4	0.56	0.78	1.1	1.6	2.2
400	630		0.64	0.9	1.2	1.8	2.6
630	1000			1	1.4	2	2.8
1000	1600				1.6	3.2	3.2
1600	2500					3.6	3.8
2500	4000						4.4
4000	6300
Size		Tolerance(mm)
>	≤	CT9	CT10	CT11	CT12	CT13	CT14
	10	1.5	2	2.8	4.2	–	–
10	16	1.6	2.2	3	4.4	–	–
16	25	1.7	2.4	3.2	4.6	6	8
25	40	1.8	2.6	3.6	5	7	9
40	63	2	2.8	4	5.6	8	10
63	100	2.2	32	4.4	6	9	11
100	160	25	3.6	5	7	10	12
160	250	2.8	4	5.6	8	11	14
250	400	3.2	4.4	6.2	9	12	16
400	630	3.6	5	7	10	14	18
630	1000	4	6	8	11	16	20
1000	1600	4.6	7	9	13	18	23
1600	2500	5.4	8	10	15	21	26
2500	4000	6.2	9	12	17	24	30
4000	6300	7	10	14	20	28	35

Casting tolerance is generally divided into two categories: linear tolerance and geometric tolerance.

Linear Tolerance

This refers to the allowable deviation in distances between two points, such as diameter, radius, width, depth, height, or center-to-center measurements. The standard unit for these dimensions is millimeters (mm), which is implied if not explicitly stated.

At China Metal Castings, we tailor our investment casting processes to meet your specific tolerance requirements. If you need a reliable precision casting supplier, contact us to discuss your project’s exact tolerances.

Geometric Tolerance

Geometric tolerances include shape tolerance and position tolerance (which further consists of orientation and location tolerance). Every component consists of points, lines, and surfaces—collectively called features. Manufacturing processes inevitably introduce slight deviations from ideal geometries, affecting part functionality. To ensure performance, these tolerances must be clearly defined in designs and marked on drawings using standardized symbols.

Below is a breakdown of geometric tolerances:

Shape Tolerance

1. Straightness (─) – Limits deviation of an actual line from a perfectly straight line.

2. Flatness (▱) – Restricts how much a surface can deviate from an ideal plane.

3. Roundness (○) – Controls the variation of a circular cross-section from a perfect circle.

4. Cylindricity (⌭) – Ensures the entire cylindrical surface (including roundness and axial straightness) meets precision requirements.

5. Profile of a Line (⌒) – Governs the accuracy of non-circular curves.

6. Profile of a Surface (⏥) – Regulates the shape accuracy of complex surfaces.

Orientation Tolerance

1. Parallelism (∥) – Ensures a feature remains equidistant from a reference plane or axis.

2. Perpendicularity (⊥) – Maintains a 90° angle relative to a datum.

3. Angularity (∠) – Controls a specified angle (other than 90°) between features.

Location Tolerance

1. Concentricity (◎) – Keeps the axes of two features aligned.

2. Symmetry (☰) – Ensures features are evenly distributed around a central plane or axis.

3. Position (⊕) – Defines allowable deviation from an ideal location, determined by datums and theoretical dimensions.

Runout Tolerance

1. Circular Runout (↗) – Measures radial variation during one full rotation (no axial movement).

2. Total Runout (↗↗) – Assesses combined radial and axial variation during continuous rotation.