Shrinkfitting

Shrinkfitting is a joining technique that creates an interference fit by exploiting thermal expansion and contraction. Typically, a part with a bore, such as a hub, sleeve, gear, or pulley, is heated to expand the bore, or the mating shaft is cooled to reduce its diameter. The parts are assembled when at different temperatures, and as they return to ambient conditions the bore and shaft grip one another, producing a tight, reversible joint without fasteners or adhesives.

Process and methods include heating the outer component by induction, furnace, or hot oil to achieve sufficient expansion, then quickly placing it over the shaft and allowing the assembly to cool. Alternatively, the shaft can be cooled or the bore heated depending on the design. Proper alignment, fixturing, and controlled heating prevent damage to bearing surfaces and surface finishes. Tolerances are selected to achieve the desired interference, often guided by standard fits.

Applications cover mounting gears, pulleys, couplings, bearings onto shafts, sleeves, and flanges in automotive, industrial, and machine-tool equipment. Common materials are steel, cast iron, and various alloys; aluminum and other lighter metals can be accommodated under careful temperature control. Surface coatings and lubricants may be used to facilitate assembly or protect mating surfaces during heating.

Advantages include high clamping strength, absence of fasteners, good alignment, and potential sealing against contaminants. Disadvantages involve the need for heating and cooling equipment, risk of thermal damage or residual stresses, limited disassembly options, and reduced suitability for fragile or heat-sensitive parts. Proper process control and tooling are essential to ensure reliability.