Mechanical Attachments

How parts are joined: bonded/welded joints, non-threaded fasteners (pins, rivets, keys), and threaded fasteners (bolts).

What the problems look like

Joint and fastener sizing/checking — welded joints (throat area, weld shear, eccentric weld groups); bolted joints (preload, proof strength, tension/shear, bolt groups in eccentric loading); and non-threaded fasteners (pins/rivets in single or double shear, bearing). Calculation-based and moderate; the eccentric-group cases are where it gets multi-step.

By exam day you should be able to —

• size/check a welded joint (fillet throat area, weld shear stress, eccentric weld groups);
• design a bolted joint (preload, proof load, tensile/shear capacity, joint-vs-member stiffness, eccentric bolt-group shear);
• check non-threaded fasteners (pins/rivets in single vs. double shear, bearing stress).

Where people lose points

• Weld throat vs. leg size — fillet throat = 0.707 × leg.
• Single vs. double shear — forgetting the area doubles.
• Bearing vs. shear on the same pin/bolt — bearing stress σ = P/(d·t) vs. shear τ = P/A; checking the wrong mode.
• Bolt-joint load sharing — the external load splits bolt/member by the stiffness constant C = k_b/(k_b + k_m); applying the full external load to the bolt is the error.
• Proof strength vs. yield vs. tensile — using the wrong one.
• Eccentric bolt/weld group — omitting the moment-induced shear component.

Have these at your fingertips

Fillet-weld throat = 0.707·leg, bolt proof-load relations, and the shear-area formulas — plus where they sit in the Handbook.

Going deeper

• Welded & bolted joints

Part of the Machine Design & Materials depth. Practice this area with exam-real problems — the tutor walks any one you miss. → Start your 7-day free trial — no card. Or take the free practice exam first.