Understanding the characteristics of different types of bolts is crucial in engineering and construction. The question asks to identify which statement is NOT a property of unfinished bolts. Let's analyze each option provided to determine the correct answer.

Unfinished Bolts: Key Characteristics

Unfinished bolts, often referred to as ordinary bolts, black bolts, or common bolts, are a basic type of fastener widely used in various applications. They are distinct from high-strength bolts in their material composition, manufacturing process, and application.

Unfinished Bolt Properties Analysis

• Tensile Strength Property: Unfinished bolts, such as those conforming to ASTM A307 standards, typically have a specified minimum tensile strength. For A307 Grade A bolts, the minimum tensile strength is often specified as $\text{60 ksi}$ (kilo-pounds per square inch). This indicates they possess a certain level of resistance to pulling forces. Therefore, "Minimum tensile strength of 60 ksi" is a property of certain unfinished bolts.
• Induced Tension Property: Unlike high-strength bolts that are torqued to induce a specific, high, and predictable tension, unfinished bolts are generally "snug-tightened." This means they are tightened only to the point where all plies of the joint are in firm contact. As a result, the induced tension is relatively small and unpredictable. This characteristic affects their performance in resisting slip in connections. Thus, "Induced tension is relatively small and unpredictable" is a property.
• Material Composition Property: Unfinished bolts are typically manufactured from low-carbon steel or medium-carbon steel. High-carbon steel is generally used for applications requiring much higher strength, hardness, and wear resistance, such as tools, springs, or high-strength structural components, not for common unfinished bolts. Therefore, the statement "Made from high-carbon steel" is NOT a property of unfinished bolts.
• Structural Application Property: Due to their lower strength and the nature of their installation (snug-tightening), unfinished bolts are commonly used in connections for light structures, secondary members, bracing, and general construction where the precise control of slip is not critical, and where bearing-type connections are acceptable. Thus, "Used in light structures" is a property.

Unfinished Bolts Summary

Based on the analysis of the properties, the statement that is NOT a characteristic of unfinished bolts is that they are "Made from high-carbon steel." Unfinished bolts are typically made from lower strength steel grades, specifically low or medium carbon steel, to provide a balance of strength and ductility suitable for their intended applications.