For TA = 60 in-lbs with L = 8 inches and E = 2 inches reverse extension, what TW should be set?

For TA = 60 in-lbs with L = 8 inches and E = 2 inches reverse extension, what TW should be set?

• A. 80 in-lbs
• B. 60 in-lbs
• C. 70 in-lbs
• D. 90 in-lbs

Answer: (A)

Using a reverse extension changes the effective lever arm. When the extension reduces the lever by E, the actual torque at the fastener is the wrench setting times (L − E) divided by L. So TA = TW × (L − E) / L, and solving for TW gives TW = TA × L / (L − E). Plugging in the numbers: TA = 60 in-lbs, L = 8 in, E = 2 in → TW = 60 × 8 / (8 − 2) = 480 / 6 = 80 in-lbs. Therefore, set the torque wrench to 80 in-lbs.

Using a reverse extension changes the effective lever arm. When the extension reduces the lever by E, the actual torque at the fastener is the wrench setting times (L − E) divided by L. So TA = TW × (L − E) / L, and solving for TW gives TW = TA × L / (L − E).

Plugging in the numbers: TA = 60 in-lbs, L = 8 in, E = 2 in → TW = 60 × 8 / (8 − 2) = 480 / 6 = 80 in-lbs.

Therefore, set the torque wrench to 80 in-lbs.