Torque & Tension Specifications Flashcards

What is the primary purpose of applying torque to a fastener?

Answer: To develop clamp load (tension) in the joint

Torque is the input; the goal is to generate clamp load (tension) that keeps the joint together.

Approximately what percentage of applied torque is typically consumed by friction under the bolt head or nut face?

Answer: 50%

Roughly 50% of torque is lost to bearing-surface friction, 40% to thread friction, and only about 10% creates bolt tension.

Which fastener property most directly determines the relationship between torque and clamp load?

Answer: Nut factor (K)

The nut factor K encapsulates friction and geometry effects, making T = K × D × F the standard torque formula.

A grade 8 bolt and a grade 5 bolt of the same size are torqued to the same value. Which statement is correct?

Answer: The grade 8 develops higher clamp load due to higher yield strength

Higher-grade bolts have higher proof strength, so the same torque keeps them below yield while stretching them more elastically to develop greater tension.

What does 'torque-to-yield' (TTY) installation mean?

Answer: Intentionally stretching the bolt beyond its elastic limit for higher clamp load

TTY fasteners are deliberately torqued past the elastic range to achieve consistent, high clamp load; they must be replaced after disassembly.

When a torque wrench is used on an extension that adds length to the drive, what happens to the actual torque applied at the fastener?

Answer: It decreases unless a correction is applied

A rigid in-line extension changes the effective lever arm and requires a correction factor to deliver the intended torque at the fastener.

Which condition causes the greatest scatter (variability) in the torque-tension relationship?

Answer: Dry, unlubricated threads

Dry threads produce high and erratic friction coefficients, often causing ±30–40% variation in resulting clamp load for a given torque.