NCCER Millwright Practice Exam

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Study for the NCCER Millwright Exam. Empower your knowledge with quizzes that enhance understanding, and multiple-choice questions that provide hints and explanations. Get fully prepared and ace your exam!

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The correct mechanical squeeze for an O-ring is usually equal to what percentage of the O-ring?

100 percent
70 percent
50 percent
90 percent

The correct answer is: 90 percent

The correct mechanical squeeze for an O-ring is typically around 20% to 30% of its original diameter, resulting in an effective squeeze percentage of roughly 70% to 80%. Selecting 90% as the mechanical squeeze indicates that the O-ring is compressed significantly, which may lead to unnecessary stress and potential failure. Properly sizing the squeeze ensures the O-ring creates an effective seal without being overly compressed, which can compromise its elasticity and longevity. Thus, while the figure of 90% appears high, the intent of managing the integrity of the seal while maintaining functionality supports the rationale behind 70% being the more effective standard. Therefore, recognizing industry standards and the importance of maintaining optimal functioning conditions for O-rings guides professionals to consider proper installation practices and material characteristics that impact performance.