Investment Casting
Check Nut
What is an Investment Casting Check Nut?
A Check Nut, also known as a lock nut, is a hexagonal nut used to secure a threaded connection by preventing it from loosening due to vibration or torque. Commonly paired with fittings like bushings or adapters, it serves as a mechanical lock to reinforce threaded joints.
Made via the investment casting process, check nuts are dimensionally precise, corrosion-resistant, and provide reliable mechanical backup in instrumentation and piping systems.
Key Features
Leak-Proof
Jointing
Durable
Construction
Easy Installation
& Removal
Wide
Compatibility
Corrosion
Resistant
Specifications
| Specification Category | Parameter / Feature | Details / Options |
|---|---|---|
| Size Range | Nominal Size | ½” to 6″ (custom sizes available) |
| Pressure Ratings | ANSI / ASME Class | Class 150, 300, 600, 900, 1500, 2500 |
| PN Ratings | PN6, PN10, PN16, PN25, PN40, PN64 | |
| Product Types | Investment Casting Fitting | Check Nut (Full, Reducing) |
| Material Options | Carbon Steel | ASTM A216 WCB |
| Stainless Steel | ASTM A351 CF8 / CF8M / CF3 / CF3M | |
| Alloy Steel | ASTM A351 CK3MCuN, CK20MCuN | |
| Nickel Alloy | Inconel, Monel | |
| Standards & Certifications | ASTM | ASTM A351, ASTM A182 |
| ASME / ANSI | ASME B16.11 | |
| MSS | MSS SP-79, MSS SP-83 | |
| European Standards | EN 10241, EN 10226 | |
| Certifications | ISO 9001, PED 2014/68/EU, NACE MR0175, CE Marked | |
| Design Features | Check Nut Type | Full Check Nut, Reducing Check Nut |
| Wall Thickness | As per ASTM / ASME standards, schedule 40, 80 | |
| End Connections | Female / Male Threaded, Socket Weld, Flanged | |
| Pressure Class | 2000#, 3000#, 6000#, 9000# | |
| Tolerance | Thread Tolerance | As per ASME B1.20.1 / ISO 7-1 |
| Coating & Surface Finish | Anti-Corrosion Coating | Passivation, Nickel Plating |
| Surface Finish | Mill Finish, Polished, Bead Blasted | |
| Testing & Inspection | Pressure Testing | Hydrostatic, Pneumatic |
| Non-Destructive Testing | Dye Penetrant (DPT), Magnetic Particle (MPI) | |
| Destructive Testing | Tensile, Hardness, Torque Test |
Dimensions
| Fitting Type | Nominal Size (NPS) | Outside Diameter (OD) | Thread Length (T) | Overall Length (L) | Weight per Piece |
|---|---|---|---|---|---|
| Check Nut (Full) | ½” | 21.3 mm | 15 mm | 25 mm | 180g |
| Check Nut (Full) | ¾” | 26.7 mm | 18 mm | 30 mm | 250g |
| Check Nut (Full) | 1″ | 33.4 mm | 20 mm | 35 mm | 300g |
| Check Nut (Full) | 1½” | 48.3 mm | 22 mm | 40 mm | 500g |
| Check Nut (Full) | 2″ | 60.3 mm | 25 mm | 45 mm | 700g |
| Check Nut (Full) | 3″ | 88.9 mm | 30 mm | 55 mm | 1.1kg |
| Check Nut (Full) | 4″ | 114.3 mm | 40 mm | 60 mm | 1.7kg |
| Check Nut (Reducing) | 1″ × ½” | 33.4 / 21.3 mm | 20 mm | 30 mm | 250g |
| Check Nut (Reducing) | 2″ × 1½” | 60.3 / 48.3 mm | 25 mm | 45 mm | 900g |
Mechanical Properties
| Property | Value | Unit / Standard |
|---|---|---|
| Tensile Strength | 485 – 750 | MPa (Carbon Steel, Stainless Steel, Alloy Steel, Nickel Alloys) |
| Yield Strength | 170 – 450 | MPa |
| Hardness | 120 – 200 | HB (Brinell) |
| Elongation | ≥ 20 – 30 | % |
| Density | 7.8 – 8.0 | g/cm³ (Carbon Steel), 7.9 – 8.0 g/cm³ (Stainless Steel) |
| Impact Toughness | ≥ 27 – 70 | J (Charpy, grade-dependent) |
| Modulus of Elasticity (E) | ~200 | GPa |
| Fatigue Strength | 250 – 450 | MPa |
| Corrosion Resistance | Good to Excellent (SS > CS > Alloy Steel > Nickel Alloys) | – |
| Thermal Conductivity | 15 – 50 | W/m·K |
| Coefficient of Thermal Expansion | 11 – 17 ×10⁻⁶ | /°C |
| Yield Ratio (YS/UTS) | 0.40 – 0.65 | – |
| Poisson’s Ratio | 0.27 – 0.30 | – |
| Brinell Hardness Range | 120 – 200 | HB |
| Surface Finish | Mill Finish, Polished, Bead Blasted | – |
| End Connections | Male / Female Threaded, Socket Weld, Flanged | – |
| Operating Temperature Range | -46 to 600 | °C (material-dependent) |
| Pressure Rating | Class 150, 300, 600, 900, 1500, 2500 | ASME B16.11 |
Chemical Composition
| Element | SS 304 | SS 304L | SS 316 | SS 316L |
|---|---|---|---|---|
| Chromium (Cr) | 18.0 – 20.0 | 18.0 – 20.0 | 16.0 – 18.0 | 16.0 – 18.0 |
| Nickel (Ni) | 8.0 – 10.5 | 8.0 – 12.0 | 10.0 – 14.0 | 10.0 – 14.0 |
| Carbon (C) | ≤ 0.08 | ≤ 0.03 | ≤ 0.08 | ≤ 0.03 |
| Manganese (Mn) | ≤ 2.00 | ≤ 2.00 | ≤ 2.00 | ≤ 2.00 |
| Silicon (Si) | ≤ 1.00 | ≤ 1.00 | ≤ 1.00 | ≤ 1.00 |
| Phosphorus (P) | ≤ 0.045 | ≤ 0.045 | ≤ 0.045 | ≤ 0.045 |
| Sulfur (S) | ≤ 0.030 | ≤ 0.030 | ≤ 0.030 | ≤ 0.030 |
| Iron (Fe) | Balance | Balance | Balance | Balance |
| Molybdenum (Mo) | — | — | 2.0 – 3.0 | 2.0 – 3.0 |
Applications of Investment Casting Check Nuts
Construction &
Infrastructure
Automotive & Heavy
Equipment
Manufacturing &
Fabrication
Medical & Laboratory
Equipment
Electrical &
Electronics Assembly
Oil, Gas & Petrochemical
Installations
Do you have questions?
What’s the difference between a check nut and a standard nut?
Can check nuts be reused?
Are check nuts suitable for high vibration environments?
Do you offer metric sizes or special threads?
