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Small Joint Assemblies

3M Small Joint Assembly product solutions hold tight, last longer.

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Small Joint Assembly Applications

Small joints are typically irregularly shaped with only a small area available for bonding. The smaller, more irregular the joint, the greater the challenge to create a firm hold that can withstand heavy wear. Generally, they are insertion or overlap joints (or some combination of the two). They are very prominent in sporting goods, electronics, furniture, motors and electrical components.

Mortise and tenon joints rely on the strength of the wood.
Shaft-hosel designs transfer the impact force of a golf club head when striking a ball.
Small joints attached with threaded mechanical fasteners provide stiff, structural assemblies.

Small Joint Assemblies Typically Require:
- Low viscosity liquids for tight-fitting parts
- Vibration resistance
- Very high strength
- Ability to bond dissimilar materials

Common joint types and stresses in Small Joint Assemblies

Most small joint assemblies are 3-dimensional and are generally insertions such as mortise-and-tenon or tube-in-shaft. Because the joints are small, with forces being applied from multiple directions, the joint receives stress in nearly all forms – tension, compression, shear and cleavage. The insertion design of the joint allows the adhesive to handle the tension, compression and shear stresses while the substrates themselves help handle the cleavage.

Peel and Shear Stress of Overlap Joints

Some small joint assemblies are 2-dimensional with a majority of the stress applied as shear or peel/cleavage. Unlike panel-to-frame assemblies which have relatively long lineal lengths to disperse the load, small joint assemblies require very high strength adhesives capable of handling the stresses with very little area.

Product Categories for Small Joint Assembly

3M™ Scotch-Weld™ Structural Adhesives

Acrylic, epoxy and urethane structural adhesives hold over 6.8MPa (1,000psi) in overlap shear strength. Best choice for highest strength, fatigue and environmental resistance especially for metal to metal bonds.
3M™ Scotch-Weld™ Instant Adhesives

One part solvent-free adhesive that reaches handling strength in 5–10 seconds. Best for small bondlines (<10 cm²). Commonly used on rubbers and plastics. Very tight bondlines are achievable with near instant strength.
3M™ Scotch-Weld™ PUR Adhesives

One component, hot applied thermosetting adhesive with immediate strength and holding power. Final cured strength over 6.8MPa (1,000psi). Best for wood and plastic.
3M™ Scotch-Weld™ Retaining Compounds

These unique adhesives are easy-to-dispense, cure rapidly, and provide effective torque strength while resisting temperature and vibration and sealing out moisture and gasses to protect against corrosion.
3M™ Hot Melt Adhesive

100% solid, thermoplastic resins that reach bond strength in seconds. Best for wood and plastic.

Performance Factors for Small Joint Assemblies

All 3M technologies shown below are commonly used in small joint applications. Use the list below as a relative comparison of product performance.

+ = Good ++ = Better +++ = Best

PRO TIP

Most often, if a small joint assembly was previously welded, it will need to be redesigned for adhesive bonding. If a small joint assembly previously relied on mechanical fastening for strength, redesigns are not always needed, and adhesives may be used in conjunction to improve the strength and durability as-is.

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