Sleeve and cotter joint

The essentials

A sleeve and cotter joint connects two round rods that lie along the same axis and carry an axial load. The end of each rod is enlarged. A hollow cylindrical sleeve slides over both enlarged ends, and two cotters are driven through slots that pass through the sleeve and the rod ends, one cotter for each rod. The slots are made slightly wider than the cotter in the direction of the axis, arranged so that driving the cotter pulls each rod further into the sleeve, making the joint tight.

Key points

• Parts: two rods with enlarged ends, one sleeve, two cotters.
• Cotter: rectangular in section, with one edge tapered (a small taper such as about 1 in 30) so it can be driven in and wedged tightly.
• The taper is kept small so that the cotter does not slip out under load (it is self-locking).
• Clearances in the slots allow the cotter to draw the rod ends towards each other inside the sleeve.
• The rod ends are enlarged because the slot weakens the cross-section.
• The ends of the rods do not quite touch inside the sleeve, leaving a small gap.
• Use: joining round rods in tension or compression, for example tie rods.

Exam tips

• Draw the sectional front view with the sleeve hatched, both cotters in their slots, and the solid rods left unhatched where cut along their axis.
• Show the clearance in the slots clearly; examiners look for it.

Common mistakes

• Using this joint for rotating shafts that transmit torque.
• Drawing both edges of the cotter tapered.