V D G  – I N F O  S H E E T
FINE CASTING
Dimensional tolerances, surfaces, machining allowances
P690
March 1999
Contents:
1. Definition and validity
2. Purpose
3. Dimensional accuracy
4. Dimensional tolerances
5. Surface nature
6. Machining allowances
7. Additional notes
8. Further information
1 Definition and validity
1.1
Fine casting is a process by which dimensionally accurate castings of a high quality are manufactured by forming. The models produced by injection moulding are fused after making the ceramic moulds. The ceramic moulds are destroyed after casting. Therefore, both models and moulds are described as “lost”. Casting usually takes place in hot moulds.
1.2
Metals and alloys on iron, aluminium, nickel, cobalt, titanium, copper and magnesium base are fine cast.  Depending on the kind of alloy, casting takes place in air, under inert gas or in a vacuum.
1.3
The info sheet does not apply for the precious metals cast by investment casting, the products of the jewellery industry, the dental laboratory and art casting.
2 Purpose  2.1
This info sheet defines dimensional tolerances, and specifies machining allowances and surface rough-nesses which correspond with the state of the fine casting art.
It serves as a basis for an optimum economic co-operation between the fine casting producers and the fine casting customers.
2.2
The technical data specified here refer to the radiated, preserved or pickled surfaces in the as-delivered state. Exceptions must be agreed when work processes which change the dimensional tolerances are concerned.
2.3
Unless agreed otherwise, first samples are delivered with first orders. They serve for mutual object a
greement. The first samples must be examined by the customer. The foundry must be granted series release in writing after testing. Deviations acknowledged with the release or the first sample good findings are binding for production and must be transferred to the (good part) drawing.
reference group3 Dimensional accuracy
3.1  Contraction and shrinkage
Natural physical volume reduction is caused by contraction and shrinkage during rigidification and cooling of cast metals. Other influences in the production of fine castings result from the contraction of the lost models and the expansion of casting moulds when heating. The sum of these influences is taken into account accordingly by the injection mould manufacturer in the contraction dimensions. These are experience values which
depend on the casting contour, the form ceramic and the casting material but also on the special production technology of the individual fine
foundries.
Regulation compiled by the “Fine Casting” technical committee in the VDG
ASSOCIATION OF GERMAN FOUNDRY SPECIALISTS
Obtainable from the VDG-Informationszentrum Giesserei, Postfach 10 51 44, D-40042 Düsseldorf, Telephone (02 11) 68 71-254
Only to be reproduced with the permission of the Association of German Foundry Specialists
Page 2, VDG Info Sheet P 690
3.2 Reference levels and reference points
(see DIN standards brochure 7) For castings, it is necessary to dimension the drawings systematically with reference levels and reference points, so-called pickup points so that dimensional checks and subsequent processing
are in agreement. These reference levels and reference points must be defined already by the designer with the fine caster. The zero position of the reference levels is defined exactly by the dimensions of the reference points.
Fig. 1
Reference level – pickup points
The primary reference level “A” is fixed by three reference points A1, A2 and A3. It should correspond to the largest casting area.
The secondary reference level “B” has the two reference points B1 and B2 which must be assigned if possible on the longitudinal axis.  The tertiary reference level “C” only has one reference point C1 which should be in the middle of the casting or near to it.
Fig. 2
The reference levels are placed through the symmetry axis of the casting.
All reference points must be arranged so that they are not removed or changed by subsequent processing. Reference points should be on the outside surfaces of the fine casting. They may also be designed as raised or recessed surfaces. Raised reference points are of advantages in castings with narrow form and position tole-rances. When determining the reference points, make sure that these points are not within a gate area.
In case of difficult shapes, the casting can be positioned exactly by (pre-)processing of the pickup points.
3.3 Overdetermination
Overdeterminations are to be avoided in accor-dance with DIN 406. Wall thicknesses must always be specified. 3.4
Mould and ejection bevels
Mould and ejection bevels are usually unneces-sary. Exceptions due to moulding and casting technical reasons must be agreed between the fine casting supplier and the customer.
4.  Dimensional tolerances
4.1
Linear dimensional tolerances
Achievable dimensional tolerances on fine castings are dependent on the following factors: - casting material
- dimensions and form of the casting  4.1.1 Casting material
In production, the different properties of the ma-terials influence the range of dispersion of the tolerance fields. Therefore different tolerance series also apply for the different material groups in table 1.
Degree of accuracy
Material group D:  iron, nickel, cobalt
and copper based alloys  D 1 to D 3
Material group A:
aluminium and magnesium
based alloys
A 1 to A 3 Material group T:
Titanium based alloys
T 1 to T 3
4.1.2  Validity of the degrees of accuracy
Three degrees of accuracy are specified respec-tively in the material groups D, A and T.
Degree of accuracy 1 applies for all free dimen-sions.
Degree of accuracy 2 applies for dimensions to be tolerated.
Degree of accuracy 3 can only be kept for individual dimensions and must be agreed with the fine caster because additional production steps and complex tool corrections are necessary.
A-level
B-level
C-level
Page 3, VDG Info Sheet P 690
Table 1 Linear tolerances (dimensions in mm)
D 1
D 2
D 3
A 1
A 2
A 3
T 1
T 2
T 3
Nominal dimension range  Field  GTA Field  GTA Field  GTA Field GTA Field GTA Field GTA Field GTA Field  GTA Field GTA
to    6 0.3 0.24 0.2 0.3 0.240.2 0.5 0.4 0.4*over    6 to  10 0.36 0.28 0.22
0.360.280.22
0.6 0.4 0.4*
over  10 to  18 0.44 0.34 0.28 0.440.340.280.7 0.5 0.44over  18 to  30 0.52  14
0.4
13.5 0.34  13
0.52  14
0.40  13.50.34  13
0.8 0.7 0.52over  30 to  50 0.8 0.62 0.5 0.8 0.620.5    1.0  15
0.8
14.5 0.62  14
over  50 to  80 0.9 0.74
0.6 0.9 0.74
0.6    1.5
1.2 0.9 over  80 to  120    1.1
14.5 o.aa
14
0.7
13.5  1.1  14.50.88 14
0.7
13.5  1.7    1.4
1.1 over  120 to  180    1.6 15    1.3 14.5    1.0 14    1.6    1.3    1.0
2.0    1.6    1.3 over  180 to  250    2.4    1.9    1.5
1.9 15
1.5 14.5
1.2 14
2.4  15.5    1.9  15
1.5
14.5 over  250 to  315    2.6  15.5    2.2  15    1.6  14.6  2.6    2.2
1.6    3.2
2.6 over  315 to  400
3.6    2.8
2.8    2.4    1.7
3.6    2.8 over  400 to  500
4.0  16    3.2  1
5.5    3.2
15.5
2.6  15    1.9
14.5
4.0  16
3.2
15.5
over  500 to  630    5.4    4.4
4.4    3.4
5.4    4.4
over  630 to  800    6.2    5.0  16    5.0    4.0    6.2    5.0
16 over  800 to  1000 7.2  16.5  S.6    4.6
15.57.2
16.5 over  1000
to  1250
6.6
16
The casting general tolerance series CGT correspond to DIN 1680 Part 2 * CGT plus allowance
Table 2 applies for wall thickness tolerances
4.1.3  Position of the tolerance field
The position of the tolerance field to the nominal dimension is freely selectable. It is of advantage to set the tolerance field to be evenly distributed around the nominal dimension. In areas which are machine cut, the sum or difference of tolerance field and machining allowance must be noted (see sect. 6). 4.2
Form and position tolerances
Form and position tolerances limit the deviations of the form element of its theoretically more accurate
- form or
- direction of its exact  - location
independently of the actual dimension of the form element.
The form and position tolerances assume that reference levels and reference points (see sect. 3.2) are defined, based on DIN SSO 1101.
If form and position tolerances have been determined in the order, they must be specified individually according to tables 2a-d.
Table 2a:  Linear tolerances
Straightness, linear form
(dimensions in mm)
D1 D2 D3 A1 A2 A3 Nominal
dimension range  Field Field Field Field Field Field  to    6 0.15 0.12 0.10 0.20 0.18 0.15 over    6 to 10 0.18 0.14 0.12 0.20 0.18 0.15 over 10 to 18 0.25 0.20 0.15 0.20 0.18 0.15 over 18 to 30 0.30 0.25 0.20 0.20 0.18 0.15 over 30 to 50 0.40 0.35 0.25 0.30 0.25 0.20 over 50 to 80 0.60 0.45 0.30 0.35 0.30 0.25 over 80 to 120 0.80 0.60 0.45 0.50 0.40 0.30 over 120 to 180    1.10 0.80 0.60 0.70 0.50 0.
40 over 180 to 250    1.50    1.15 0.90 0.90 0.70 0.55 over 250 to 315    1.90    1.40    1.20    1.10 0.90 0.70 over 315 to 400    2.40    1.80    1.50    1.35    1.10 0.90 over 400 to 500    3.00
2.20    1.80
1.60    1.30    1.10 over 500 to 630      1.80    1.50    1.30 over 630 to 800
2.00    1.70    1.50 over 800 to 1000
2.20
1.90
1.70
Table 2b:  Form and position tolerances Flatness, area form, roundness (dimensions in mm)
Nominal
D1 D2 D3 A1 A2 A3 dimension range Field Field Field Field Field Field to    6 0.200.150.120.200.180.15 over    6 to 10 0.250.200.150.200.180.15 over 10 to 18 0.400.300.200.25
0.220.18 over 18 to 30 0.500.400.300.300.250.20 over 30 to 50 0.600.500.400.400.300.25 over 50 to 80 0.800.650.500.500.400.30 over 80 to 120    1.000.800.650.650.500.40 over 120 to 180    1.30  1.100.850.900.700.55 over 180 to 250    1.80  1.50  1.20  1.150.900.75 over 250 to 315    2.30  1.80  1.50  1.35  1.100.90 over 315 to 400    2.90  2.30  1.85  1.60  1.35  1.10 over 400 to 500    3.40  2.80  2.20  1.80  1.55  1.30 over 500 to 630    2.00  1.80  1.50 over 630 to 800    2.25  2.00  1.70 over 800 to 1000    2.50  2.20  1.90 Table 2c:  Form and position tolerances Parallelism, symmetry
(dimensions in mm)
Nominal
D1 D2 D3 A1 A2 A3 dimension range Field Field Field Field Field Field to    6 0.250.200.150.200.180.15 over    6 to 10 0.300.250.200.200.180.15 over 10 to 18 0.400.300.250.250.200.18 over 18 to 30 0.500.400.300.350.250.20 over 30 to 50 0.700.600.500.450.300.25 over 50 to 80    1.000.800.650.550.400.30 over 80 to 120    1.30  1.100.900.700.500.45 over 120 to 180    1.80  1.50  1.200.900.750.60 over 180 to 250    2.50  2.00  1.60  1.20  1.000.80 over 250 to 315    3.15  2.60  2.00  1.50  1.20  1.00 over 315 to 400    3.80  3.20  2.50  1.90  1.60  1.30 over 400 to 500    4.40  3.80  3.20  2.40  2.00  1.60 over 500 to 630    3.0
0  2.50  2.00 over 630 to 800    3.80  3.15  2.50 over 800 to 1000    4.80  4.00  3.20 Table 2d:  Form and position tolerances Parallelism, symmetry
(dimensions in mm)
Nominal
D1 D2 D3 A1 A2 A3 dimension range Field Field Field Field Field Field to    6 0.300.250.200.250.200.18 over    6 to 10 0.350.300.250.250.200.18 over 10 to 18 0.500.400.300.300.250.20 over 18 to 30 0.600.500.400.400.300.25 over 30 to 50 0.800.600.500.600.450.30 over 50 to 80    1.100.800.600.800.700.45 over 80 to 120    1.30  1.000.80  1.100.900.65 over 120 to 180    1.80  1.40  1.10  1.50  1.300.90 over 180 to 250    2.40  1.90  1.60  2.00  1.60  1.30 over 250 to 315    3.00  2.50  2.00  2.40  2.00  1.60 over 315 to 400    3.80  3.20  2.50  2.90  2.40  2.00 over 400 to 500    4.40  3.70  3.00  3.50  3.00  2.50 over 500 to 630
over 630 to 800
over 800 to 1000
Page 4, VDG Info Sheet P 690
Page 5, VDG Info Sheet P 690
The dimensions according to section 4.1.1 apply with regard to the material groups D and A.
The three degrees of accuracy are available. An increasing degree of accuracy implies increased production complexity. Degree of accuracy 3 can only be kept for individual dimensions and must be agreed with the fine caster because additional production steps and complex tool corrections are necessary.
Form and position tolerances deviating from tables 2a-d or not contained (e.g. material group T) must be agreed between customer and fine casting supplier and entered in the drawing in accordance with DIN ISO 1101.
For the material group T (titanium based alloys), no data are contained in the tables 2a-d because of the influences of normal treatment methods such as hot isostatic pressing or pickling.
4.3  Angle tolerances for the material groups
D, A and T
Table 3: Angle tolerances
Precision
1 2 3 Permissible direction deviation
Nominal dimension
angle minute
mm per 100 mm
angle minute
mm per 100 mm
angle minute
mm per 100 mm
to 30 mm 302)
0.87
302)
0.87 202)
0.58 over 30 to 100 mm 302)
0.87 202) 0.58 152) 0.44 over 100 to 200 mm 302)
0.87 152) 0.44 102) 0.29 over 200 mm
202)
0.58 152) 0.44 102) 0.29
1) The length of the short arm is decisive for the nominal dimension range. 2)
The angle may deviate in both directions.
Angle tolerances deviating from table 3 must be agreed with the fine caster and entered in the drawing in accordance with DIN ISO 1101. 4.4  Rounding radius
The given tolerances apply for the material groups D, A and T. Table 4:
Rounding radius for the material groups D, A and T
Degree of accuracy
Nominal dimension range 1)
mm
1 2 3  to ± 0.30 ± 0.20 ± 0.15
over 5 to 10 ± 0.45 ± 0.35 ± 0.25
over 10 to 120 ± 0.70 ± 0.50 ± 0.40
over 120 linear (see table 1)
Rounding radius deviating from table 4 must be agreed with the fine caster.
4.5  Dimension tolerances for wall thicknesses
The wall thickness tolerances depend on
– the size of the (ceramic) walls of the casting mould which form them,  – its uninterrupted area,
– its possible thermal distortion,
– the metallostatic pressure of the liquid metal. The wall thickness tolerances therefore do not depend on the degree of accuracy. They are limited (or reduced) by thicker edge parts, breakthroughs (openings, holes), stems, ribs and similar to be cast, which “relieves” the wall thickness.
The tolerance range in question can be taken from table 5. The smallest side length of an area decisive for the wall thickness tolerance is noted therein.  Fig. 3
Case “A”
Case “B”
Case A: The area formed by dimensions a and b is not interrupted. Dimension b is smaller than dimension a. Dimension b determines the wall thickness tolerance.
Case B: The area formed by dimensions a and b is interrupted by a centre bore. The uninterrupted area is therefore formed by the dimensions b and c. Dimension c is smaller than dimension b.
Dimension c determines the wall thickness toler-ance to be provided. Table 5:  Wall thickness tolerances
Smallest side length of an area (Fig. 3) Material group D  Fe, Nf, Co, Cu based alloys Material group A AI and Mg based alloys
Material group T
Ti based alloys mm mm mm mm
to 50 ± 0.25 ± 0.25 ± 0.30
over 50 to 100 ± 0.30 ± 0.30 ± 0.40
over 100 to 180 ± 0.40 ± 0.40 ± 0.50 over 180
to 315
± 0.50 ± 0.50 ± 0.60 over 315
± 0.60
± 0.60
± 0.70
wall thickness “s”

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