Casting Geometric Tolerances (GD&T) Charts: Straightness, Flatness, Roundness, Parallelism, Perpendicularity, Concentricity Tolerance Tables

Here we list all Casting GD&T Charts covering all geometric tolerances (straightness, flatness, roundness, parallelism, perpendicularity tables)!

 

Casting Geometric Tolerance Charts

In metal casting and manufacturing, maintaining tight tolerances is crucial for ensuring the quality and functionality of cast parts. Casting tolerances define the allowable variation in dimensions and geometries of a cast part. Common casting tolerances specify limits on straightness, flatness, roundness, parallelism, and perpendicularity. Exceeding these tolerances can lead to problems assembling or fitting together cast components. This article provides comprehensive casting tolerance charts covering key geometrical tolerances for cast parts. The tables define standard tolerance grades for straightness, flatness, roundness, parallelism, and perpendicularity of castings made from various metal alloys. Understanding these standard tolerance values can help engineers and manufacturers design and produce precision metal cast parts that fall within acceptable variation limits. Referring to these casting tolerance charts helps ensure cast parts meet functionality and quality requirements.

 

What are Casting Tolerances?

Casting tolerances refer to the allowable deviation or variation in dimensions and other characteristics of a cast part. These tolerances are defined to ensure that the final cast product meets the desired specifications and functional requirements. Casting tolerances can vary depending on factors such as the casting method, material, size, and specific application. It is common for casting tolerances to be specified using industry standards, engineering drawings, or customer requirements, and they typically take into account factors like part geometry, material shrinkage, tooling capabilities, and manufacturing processes.

 

Casting Geometric Tolerance Grade

Casting geometric tolerance grade refers to the level of permissible variation in the dimensions and geometric features of a casting part. It is defined by a standard set of symbols and values known as geometric dimensioning and tolerancing (GD&T). The casting geometric tolerance grade specifies the allowable tolerance limits for various aspects such as size, form, orientation, and position of features on the casting. These tolerances help ensure that the casting meets the desired design requirements and can function properly in its intended application.

Casting GD&T Grades

Methods	Geometric Tolerance Grades
	Carbon steel	Gray cast iron	Ductile cast iron	Malleable cast iron	Copper alloys	Zinc alloys	Soft metal alloys	Nickel-based alloys	Tool steel alloys
Sand casting Manual molding	6-8	5-7	5-7	5-7	5-7	5-7	5-7	6-8	6-8
Sand casting Machine molding and shell molding	5-7	4-6	4-6	4-6	4-6	4-6	4-6	5-7	5-7
Metal casting (excluding pressure casting)	–	–	–	–	3-5	–	3-5	–	–
Pressure casting	–	–	–	–	2-4	2-4	2-4	–	–
Investment casting	–	3-5	3-5	3-5	3-5	2-4	3-5	–	–

The values in this table generally apply to castings with nominal sizes larger than 25mm. For smaller-sized castings, the following finer dimensional tolerances are typically guaranteed:

1) For castings with a nominal size ≤ 10mm, the precision level is increased by three levels.

2) For castings with a nominal size between 100mm and 16mm, the precision level is increased by two levels.

3) For castings with a nominal size between 16mm and 25mm, the precision level is increased by one level.

 

Casting Tolerance Charts (Casting GD&T Tables)

Casting tolerances are the acceptable deviations from the desired dimensions and properties of a casting. These tolerances are specified by the designer or engineer and are used to ensure that the final product meets the required specifications.

There are several types of casting tolerances, including:

Casting Straightness Tolerance (mm)

Nominal Size		GCTG and Corresponding Straightness Tolerance
>	=	CGTG2	CGTG3	CGTG4	CGTG5	CGTG6	CGTG7	CGTG8
–	10	0.08	0.12	0.18	0.27	0.4	0.6	0.9
10	30	0.12	0.18	0.27	0.4	0.6	0.9	1.4
30	100	0.18	0.27	0.4	0.6	0.9	1.4	2
100	300	0.27	0.4	0.6	0.9	1.4	2	3
300	1000	0.4	0.6	0.9	1.4	2	3	4.5
1000	3000	–	–	–	3	4	6	9
3000	6000	–	–	–	6	8	12	18
6000	10000	–	–	–	12	16	24

 

Casting Flatness Tolerance

Nominal Size		GCTG and Corresponding Flatness Tolerance
>	=	CGTG2	CGTG3	CGTG4	CGTG5	CGTG6	CGTG7	CGTG8
–	10	0.12	0.18	0.27	0.4	0.6	0.9	1.4
10	30	0.18	0.27	0.4	0.6	0.9	1.4	2
30	100	0.27	0.4	0.6	0.9	1.4	2	3
100	300	0.4	0.6	0.9	1.4	2	3	4.5
300	1000	0.6	0.9	1.4	2	3	4.5	7
1000	3000	–	–	–	4	6	9	14
3000	6000	–	–	–	8	12	18	28
6000	10000	–	–	–	16	24	36	56

 

Casting Roundness, Parallelism, Perpendicularity, and Symmetry Tolerance

Nominal Size		GCTG and Corresponding Geometric Tolerance
>	=	CGTG2	CGTG3	CGTG4	CGTG5	CGTG6	CGTG7	CGTG8
–	10	0.18	0.27	0.4	0.6	0.9	1.4	2
10	30	0.27	0.4	0.6	0.9	1.4	2	3
30	100	0.4	0.6	0.9	1.4	2	3	4.5
100	300	0.6	0.9	1.4	2	3	4.5	7
300	1000	0.9	1.4	2	3	4.5	7	10
1000	3000	–	–	–	6	9	14	20
3000	6000	–	–	–	12	18	28	40
6000	10000	–	–	–	24	36	56	80

 

Casting Concentricity Tolerance

Nominal Size		GCTG and Corresponding Concentricity Tolerance
>	=	CGTG2	CGTG3	CGTG4	CGTG5	CGTG6	CGTG7	CGTG8
–	10	0.27	0.4	0.6	0.9	1.4	2	3
10	30	0.4	0.6	0.9	1.4	2	3	4.5
30	100	0.6	0.9	1.4	2	3	4.5	7
100	300	0.9	1.4	2	3	4.5	7	10
300	1000	01.4	2	3	4.5	7	10	15
1000	3000	–	–	–	9	14	20	30
3000	6000	–	–	–	18	28	40	60
6000	10000	–	–	–	36	56	80	120