Aircraft Bolts: What Do Cross or Asterisk Marks Indicate?

What do aircraft bolts with a cross or asterisk marked on the bolt head represent?

Aircraft bolts with a cross or asterisk on the bolt head usually indicate close tolerance bolts, which are necessary for applications requiring precision and accuracy rather than being a sign that the bolts are made of aluminum alloy or standard steel.

Understanding Aircraft Bolts and Their Markings

Aircraft bolts play a critical role in the construction and maintenance of aircraft. Each bolt is carefully designed and manufactured to meet specific requirements depending on the application it will be used for. One key aspect of identifying aircraft bolts is the marking on the bolt head, which serves as an important indicator of the bolt's specific characteristics.

When examining an aircraft bolt and noticing a cross or asterisk marked on the bolt head, it is essential to understand that this marking does not necessarily denote the material the bolt is made of, such as aluminum alloy or standard steel. Instead, this marking signifies that the bolt is a close tolerance bolt.

The Significance of Close Tolerance Bolts

Close tolerance bolts are specially designed to provide precise fits and accuracy in applications where standard bolts may not suffice. These bolts are crucial in situations where tight tolerances are required to ensure the safety and reliability of the aircraft.

Close tolerance bolts are preferred in scenarios where vibrations, stress, or environmental factors could potentially lead to bolt failure if a standard bolt were used. By utilizing close tolerance bolts marked with a cross or asterisk, aircraft engineers and maintenance professionals can ensure that every bolt used in the aircraft meets the necessary standards for precision and quality.

It is important to note that different types of bolts may have unique markings on their heads to distinguish their specific characteristics. Therefore, when working with aircraft bolts, it is imperative to pay close attention to these markings to select the appropriate bolts for each application and to maintain the safety and integrity of the aircraft.