Investment casting, also known as precision casting or lost wax casting, is a manufacturing process used to create intricate and complex metal parts. Tolerances in investment casting refer to the acceptable variations or deviations from the specified dimensions or features of a cast part. Achieving tight tolerances is crucial in ensuring that the final product meets design requirements and performs as intended. The tolerance levels in investment casting depend on various factors, including the material used, part geometry, and the capabilities of the foundry. Here are some general considerations regarding investment casting tolerances:

1,Part Complexity: Parts with intricate features, thin walls, or complex geometries may have looser tolerances compared to simpler designs. Achieving tight tolerances becomes more challenging with increasing complexity.

2,Material Selection: The type of metal or alloy used in the casting process can influence achievable tolerances. Some materials may exhibit greater shrinkage during cooling, affecting the final dimensions of the cast part.

3,Size of the Part: Larger parts may have looser tolerances compared to smaller parts. Controlling dimensions becomes more challenging with increasing size.

4,Casting Method: Different investment casting methods may have varying tolerances. For example, the traditional lost wax process may have different tolerances compared to newer technologies or variations of the process.

5,Quality Control Measures: The implementation of stringent quality control measures and inspection processes can help ensure that the final cast parts meet the specified tolerances. This may include the use of advanced measuring tools and techniques.

6,Experience of the Foundry: The expertise and experience of the foundry in investment casting play a significant role in achieving tight tolerances. Established foundries with a history of precision casting are often better equipped to meet strict tolerance requirements.

7,Customer Requirements: Tolerance specifications are typically outlined in the customer’s design requirements or drawings. It’s essential for the foundry and the customer to communicate clearly about the acceptable tolerance levels for a given project.

8,Surface Finish: Tolerances may be influenced by the desired surface finish of the cast part. Parts requiring a high degree of surface smoothness or intricate details may have different tolerance considerations.

It’s important for designers and engineers to work closely with the foundry during the design phase to understand the limitations and capabilities of the investment casting process, ensuring that the specified tolerances are achievable. Additionally, communication between the customer and the foundry is crucial to establish clear expectations regarding tolerances and quality standards.

2. Tolerances

INVESTMENT CASTING TOLERANCES
InchesMillimeters
DimensionToleranceDimensionTolerance
Up to 0.500±.004″Up to 12.0± 0.10mm
0.500 to 1.000”±.006″12.0 to 25.0± 0.15mm
1.000 to 1.500”±.008″25.0 to 37.0± 0.20mm
1.500 to 2.000”±.010″37.0 to 50.0± 0.25mm
2.000  to 2.500”±.012″50.0 to 62.0± 0.30mm
2.500 to 3.500”±.014″62.0 to 87.0± 0.35mm
3.500 to 5.000”±.017″87.0 to 125.0± 0.40mm
5.000 to 7.500”±.020″125.0 to190.0± 0.50mm
7.500 to 10.000”±.022″190.0 to 250.0± 0.57mm
10.000 to 12.500”±.025″250.0 to 312.0± 0.60mm
12.500 to 15.000±.028″312.0 to 375.0± 0.70mm
Ferritic Stainless Steels
AlloyTensile StrengthMaximum Use TempMelting PointResistance
405585 MPa
(85Ksi)
815˚C
(1,499˚F)
1,480 – 1,530˚C
(2,700 – 2,790˚F)
Good acid corrosion resistance
408505 MPa
(73 Ksi)
815˚C
(1,499˚F)
1,400 – 1,455˚C
(2,550 – 2,650˚F)
Resists well against most
oxidizing acids and salt spray
409 448MPa
(65 Ksi)
815˚C
(1,499˚F)
1,425 – 1,510˚C
(2,597 – 2,750 F)
Good corrosion resistance
420 760 – 1702 MPa
(110 – 247 Ksi)
427˚C
(800˚F)
1,455 – 1,510˚C
(2,651 – 2,750 F)
Fairly corrosion resistant
430450 MPa
(65 ksi)
815˚C
(1,499˚F)
1,425 – 1,510˚C
(2,597 – 2750˚F)
Good nitric acid resistance
434540 MPa
(78 ksi)
815˚C
(1,499˚F)
1,426 – 1,510˚C
(2,600 – 2750˚F)
Superior pitting resistance
436459 MPa
(67 Ksi)
815˚C
(1,499˚F)
1,425 – 1,510˚C
(2,600 – 2,750˚F)
Excellent citric and nitric
acid corrosion resistance
442515-550 MPa
(77 – 80Ksi)
925-980˚C
(1,700/1,800˚F)
1,065 – 1,120˚C
(1,950 – 1,120˚F)
Good corrosion resistance
444415 MPa
( 60 Ksi)
950˚C
(1,752˚F)
1,405 – 1,495˚C
(2,561 – 2,723˚F)
Good oxidation resistance
Martensit Stainless Steels
AlloyTensile StrengthMaximum Use TempMelting PointResistance
410500 -1400 MPa
(73 – 203 Ksi)
650˚C
(1,202˚F)
1,482 – 1,532˚C
(2,700 – 2,790˚F)
Good corrosion resistance to
air, water, and some chemicals
410S 444 MPa
(64 Ksi)
705˚C
(1,300˚F)
1,482 – 1,532˚C
(2,700 – 2,790˚F)
Good oxidation resistance
416517 MPa
(75 Ksi)
760˚C
(1,400˚F)
1,480 – 1,530˚C
(2,696 – 2,786˚F)
Poor Chloride resistance. Good
resistance to acids, alkalis & fresh water
4201,586 MPa
(230 ksi)
650˚C
(1,202˚F)
1,454 – 1,510˚C
(2,649 – 2,750˚F)
Resistant to mild acids, alkalis,
and water when hardened
440758 MPa
(110 Ksi)
760˚C
(1,400˚F)
1,483˚C
(  2,700˚F)
Limited corrosion resistance
Duplex (Ferritic-Austenitic) Stainless Steels
AlloyTensile StrengthMaximum Use TempMelting PointResistance
2205620 MPa
(90 Ksi)
300˚C
(572˚F)
1,385 – 1,443˚C
(2,525 – 2,630˚F)
Excellent corrosion resistance
2304>600 MPa
(>87 Ksi)
570˚C
(1058˚F)
900 – 1,150˚C
(1,650 – 2,100˚F)
Resistance to corrosion cracking
2507800 MPa
(116 Ksi)
300˚C
(572˚F)
1,350˚C
(2,460˚F)
Excellent chloride corrosion resistance
Precipitation Hardening (PH) Stainless Steels
AlloyTensile StrengthMaximum Use TempMelting PointResistance
17-41103 MPa
(160 Ksi)
316˚C
(600˚F)
1,404 – 1,440˚C
(2,560 – 2,625˚F)
Excellent corrosion resistance
15-51380 MPa
(200 Ksi)
316˚C
(600˚F)
1,404 – 1,440˚C
(2,560 – 2,625˚F)
Excellent corrosion resistance

3. Carbon Steel

ASTM A216 Cast Carbon Steel
AlloyTensile StrengthMaximum Use TempMelting PointResistance
WCA500 MPa
(73 Ksi)
400˚C
(700˚F)
1410 – 1,460˚C
(2,580 – 2,650˚F)
Excellent corrosion resistance
WCB570 MPa
(83 Ksi)
426˚C
(800˚F)
1410 – 1,460˚C
(2,580 – 2,650˚F)
Excellent corrosion resistance
WCC655 MPa
(95 Ksi)
538˚C
(1000˚F)
1410 – 1,460˚C
(2,580 – 2,650˚F)
Excellent corrosion resistance
SAE-AISI 1020 steel 
AlloyTensile StrengthMaximum Use TempMelting PointResistance
1020460 MPa
(63 Ksi)
400˚C
(700˚F)
1420 – 1,460˚C
(2,590 – 2,650˚F)
Excellent corrosion resistance
1020430 MPa
(62 Ksi)
400˚C
(700˚F)
1420 – 1,460˚C
(2,590 – 2,650˚F)
Excellent corrosion resistance

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