Rank the four common torque-transmission methods from strongest to weakest.

• A. Splines; Keyways/Pin joints; Set screws; Press/interference fit
• B. Press/interference fit; Set screws; Keyways/Pin joints; Splines
• C. Splines; Set screws; Keyways/Pin joints; Press/interference fit
• D. Keyways/Pin joints; Splines; Press/interference fit; Set screws

Answer: (A)

Transmitting torque effectively comes from how reliably the two parts are held together and how much contact and interlock there is at the interface. Splines create a continuous interlock along the shaft and hub, so the torque is carried across many teeth with even load sharing. That large, positive engagement resists slip far better than other methods, giving the highest torque capacity.

Next, keyways with pins provide a positive drive by locating the parts and sharing load through a few solid interfaces, but they have less contact area and are more prone to shear or wear at the key or pin and at the corners of the keyway. They’re strong, but not as robust as splines.

Set screws rely on clamping friction between the hub and shaft. The torque capacity depends on the clamping force, surface finish, and how well the connection stays tight under vibration or cyclic loading. This makes them more prone to slip and loosening than interlocked or keyed connections, so they’re weaker than splines and keyways/pins.

Press or interference fits transmit torque entirely by friction at a mating interface. While they can be very strong initially, their performance is highly sensitive to surface finish, alignment, and thermal effects, and they’re hard to disassemble. Reliability under varying conditions is typically lower, so they’re considered the weakest option in this ranking.

So, strongest to weakest: splines, then keyways/pin joints, then set screws, with press/interference fits as the weakest.