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Dimension Inspection of Bolts and Nuts

Bolts size:

Nominal diameter (d): calipers or micrometers to measure the thread diameter, the error needs to be within the standard allowable range.

Length (L): measure the distance from the top of the head of the bolt to the end of the screw (all-thread bolts to measure the length of the thread), the tolerance needs to be in line with the requirements;

head size: the head of the opposite side of the width (s), the thickness (k), measured by calipers, to ensure that the nut or wrench with the match.

Nuts size:

Nominal Diameter (D): Measure the small diameter of the thread, and the bolt thread match;

Thickness (m): the height of the nut, affecting the length of the thread engagement, need to meet the standard;

Width of the opposite side of the (s): the size of the wrench with the allowable error in the range.

Thread accuracy inspection:

Use thread pass/stop gauge (plug gauge to measure bolt external threads, ring gauge to measure nut internal threads) to detect: the pass gauge should be able to be screwed in smoothly, and the stop gauge should be screwed in at a length of not more than 1-2 threads (according to the standard);

If necessary, use the thread micrometer to measure the thread center diameter to ensure that it is in the tolerance range (the center diameter has a direct impact on the looseness or tightness of the thread fit).

ASTM A193 Grade B7 Stud Bolts 

ASTM A193 is a standard specification covering alloy steel and stainless steel bolting materials for pressure vessels, valves, flanges, and fittings used in high temperature or high pressure service conditions. Among them, B7 is the most commonly used grade.

ASTM A193 Grade B7 Stud Bolts Specification

ASTM A193 Grade B7 Chemical Composition

ASTM A193 B7 Mechanical Property

ASTM A354 Nuts

The STM A354 standard mainly defines the chemical and mechanical property requirements for quenched and tempered alloy steel bolts, studs and other externally threaded fasteners, which are generally 4 inches in diameter and below and are used in services requiring high strength and limited high-temperature applications. The standard itself does not directly specify the brand of nuts, but recommends specific nut brands under the ASTM A563 standard for use with A354 bolts to ensure that the expected load-bearing capacity and reliability can be achieved when the bolt and nut are combined.

ASTM A354 Grades

ASTM A354 Nuts Chemical Composition

ASTM A354 Nuts Mechanical Property

Application Scenarios

Industrial manufacturing: mechanical machine tools, automobiles, ships, aerospace and other equipment parts fixed (such as engine block, chassis frame);

Construction: steel bridge, housing frame, pipeline bracket connection

Daily necessities: furniture assembly, home appliances, bicycles, medical equipment, etc.

Special environments: chemical pipelines, nuclear power equipment, marine platforms, etc., the need for corrosion-resistant, high-temperature-resistant special materials Bolts and Nuts

Installation and Maintenance Precautions

Matching: The specifications  and strength level of bolts and nuts must be matched exactly to avoid fracture due to mismatch of strength (e.g., high-strength bolts with low-strength nuts may lead to nut slippage).

Pre-tightening force control: When tightening, the pre-tightening force should be controlled according to the design requirements, too loose may lead to loosening of the connection, and too tight may cause the bolt to fracture or deformation of the connected parts (torque wrenches should be used on important occasions).

Anti-loosening measures: In the vibration environment, anti-loosening nuts, spring washers, spot welding and other ways to prevent loosening.

Corrosion protection: In wet or corrosive environments, it is necessary to choose stainless steel materials or surface treatment of bolts and nuts (such as galvanized, chrome-plated, coated with antirust paint).

The post Alloy Steel Stud Bolts and Nuts Order appeared first on Supplier of Quality Forged Fittings-Flanges.

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ASTM A490 Type 3 Heavy Hex Bolts Specification

ASTM A490 bolts are heavy hex bolts made of alloy steel with a flat bearing surface, washer faced, and chamfered point. They are used in structural steel joints in heavy construction applications that require greater yield and tensile strengths than those of an A325 bolt are required. They are available in diameters ranging from ½” up to 1-1/2” and come in two types.

Type 1 bolts are made from alloy steel, and Type 3 is made from a weathering steel, which is approximately twice as resistant to corrosion as Type 1. These Type 3 A490 bolts shall be marked “A490” to set them apart from standard A490 bolts.

A490 Types

A490 ASTM A490 Type 3 Chemical Properties

A490 ASTM A490 Type 3 Mechanical Properties

Heavy Hex Bolts Tensile Properties

^A The stress area is calculated as follows:

A.=0.7854[D-(0.9743/n)]²

where:

A – stress area, in.²

B – nominal bolt size, and

C – threads per inch.

^B Loads tabulated and loads to be used for tests of full-size bolts larger than 1% in. in diameter are based on the following.

Inspecting ASTM A490 Type 3 Heavy Hex Bolts

Dimensional measurement:

Use measuring tools such as calipers and micrometers to check the dimensions of the bolts, including diameter, length, thread size, etc.

Ensure that the dimensions meet the relevant standards and design requirements.

Appearance inspection:

Visually inspect the surface of the bolts to check for defects such as cracks, scratches, rust, etc.

Check whether the threads are complete and the head shape is correct.

Heavy Hex Bolts Key Advantages

Enhanced Corrosion Resistance:

High Strength:  

Suitability for Outdoor Environments:

Reduced Maintenance

Important Considerations:

While the weathering steel provides corrosion resistance, it’s essential to understand that it’s designed for specific environmental conditions. They are not suitable for all environments, particularly those with excessive chloride exposure (e.g., coastal areas with high salt content).

The selection of compatible washers and nuts is crucial for optimum performance.

 It is very important to remember that certain coatings can cause hydrogen embitterment in high strength bolts, like A490 bolts, and are therefor prohibited.

In essence, ASTM A490 Type 3 bolts offer a combination of high strength and improved corrosion resistance, making them a reliable choice for demanding structural applications.

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