Bonding Process Archives - Transmission Digest
Fine-Tuning the Bonding Process

In a torque converter the friction material most often used on a lockup piston or cover is a mix of fibrous materials in a phenolic resin. The adhesive used to bond this material to steel is also phenolic based. Phenolic is a thermo-set type of plastic, and this plastic has unique properties.

The Proper Surface Finish for Bonding (an Eye Opener)

Choosing the correct surface finish for bonding can be controversial. Some rebuilders claim you can bond to a surface as smooth as glass, provided the bond-line temperature and the compression pressure are correct. Others claim that a very rough surface finish is needed for a good bond. The finish of a machined surface is rated on a roughness-average (RA) scale.