Technical FAQs

Bolt Thread Length

Is there a standard thread length for bolts?

Depending on the type of bolt you are using the thread length can vary greatly. There is not an inclusive thread length standard that covers all fasteners. Depending on the applications, manufacturer, and a number of other factors the amount thread may change. It is important to clearly communicate at time of purchase your desired... Read more

Tie Rod Assembly Configurations

How are tie rods, turnbuckles, and clevises configured?

Tie rods, clevises, and turnbuckles are an important part of many architectural designs. Canopy supports, structural steel bracing, and walkway hangers are a few of the applications that use these assemblies. The unique configuration allows for field adjustments in both length and tension. Adjustment Adjustments are possible by threading opposing ends of the rod right hand... Read more

Concerns Calculating Torque

How do I calculate torque for construction fasteners?

Torque is a difficult value to calculate accurately, especially for construction fasteners and should be used cautiously. The primary challenge is accounting for environmental factors, coatings, and a number of other variables including surface texture, material hardness, and thread series. In most situations, it is challenging to give reliable allowable torque values for bolted assemblies.... Read more

Lag Screw Shear Strength

How do I determine the shear capacity and strength of lag screws?

Unfortunately, we have no specific data to answer this question. First, “standard” lag bolts that are readily available in the marketplace are ungraded, meaning they are not manufactured to any ASTM specification and have no verifiable mechanical requirements. Therefore, it is impossible to determine the strength characteristics of a lag screw unless they are custom... Read more

Rotational Capacity Testing

What is rotational capacity (ROCAP) testing?

Per ASTM F3125 Annex section 2.1.1, the rotational capacity test is defined as a test, “intended to evaluate the presence of a lubricant, the efficiency of lubricant and the compatibility of assemblies.” In a 1970 study referenced by the Research Council on Structural Connections (RCSC), it was shown that galvanizing increases the friction between the... Read more

Clevis Pin Question

When using a clevis pin and using a cotter pin, or a spring pin, or a spring clip, or a retaining ring to capture the outer end, my practice has always been to place a washer under the retaining device to discourage deformation and/or loss of the retaining device due to rotation of the clevis pin. Who agrees out there?

It seems like this question is directed toward clevis pins that are used to connect control assemblies, linkages and perhaps hinges. In these applications where rotation of the clevis pin is anticipated, I agree that a washer would protect the retaining device from possible ‘side effects’ of the rotation. In the case of pins that... Read more

Grade 8 vs ASTM A325

Is a Grade 8 bolt the same as an ASTM A325?

ASTM A325 and SAE J429 grade 8 are not the same fastener. As a matter of fact, they couldn’t be more different. SAE (Society of Automotive Engineers) establishes specifications covering fasteners intended for use in automotive, OEM, and equipment applications, while ASTM (American Society for Testing and Materials) provides specifications for construction fasteners. There are... Read more

RA% = “Reduction of Area”

What is "Reduction of Area (RA%)"?

RA% is a term that stands for “reduction of area percentage.” It is an important requirement of the ASTM F1554 specification, in addition to other specifications. This value is reported as a percentage of the original test piece. When fasteners undergo mechanical testing, they are pulled to failure and the diameter of the point at which... Read more

Fastener Head Markings Decoded

Sometimes there are lines on the bolt head. What do they mean?

The lines on the head of a bolt indicate its grade. SAE J429 (Society of Automotive Engineers) bolts have radial lines, whereas ASTM (American Society for Testing and Materials) uses a combination of letters and numbers to indicate the grade. Three radial lines will indicate an SAE grade 5 fastener, while six radial lines will... Read more

Tension vs. Torque

Can someone explain how tension and torque relates to bolted connections?

We’ll try our best. The relationship between tension and torque should be looked at cautiously, since it is very difficult to indicate the range of conditions expected to be experienced by a fastener. Torque is simply a measure of the twisting force required to spin the nut up along the threads of a bolt, whereas... Read more