How do you calculate the bearing size for a Tufnol bush?

Sizing a Tufnol bush follows normal engineering practice with two laminate-specific allowances. Aim for a length-to-shaft-diameter ratio of about 1:1 (long bearings over 2:1 trap heat), keep wall thickness modest to help dissipate heat, and set the initial running clearance to allow for the small dimensional growth as the laminate absorbs moisture and for bore closure when a bush is press-fitted. The exact clearances and worked allowances are set out in the bearing dimensions calculation guide.

Can Tufnol bearings run dry without lubrication?

Yes, in less demanding applications. Most Tufnol cotton fabric grades are not self-lubricating, so a lubricant is preferred to reach their full load and wear performance, but they will run dry where loads and speeds are modest. Where a true dry bearing is needed, Grade 2F/3/PTFE carries PTFE powder through the laminate to give self-lubricating, low-friction running. See the self-lubricating options on the special bearing grades page.

Phenolic is a thermosetting resin (phenol formaldehyde) that sets hard and heat-stable once cured. In laminate form, the form Tufnol makes, layers of paper or woven cotton are impregnated with phenolic resin and pressed under heat to create a strong, rigid material with good electrical insulation and excellent machinability. It is the basis of Tufnol's paper (SRBP) and cotton fabric (SRBF) grades. See the phenolic paper grades on the paper laminates page.

Tufnol Materials - Laminated Phenolic Bearings

Tufnol laminated-bearing materials are widely used where tough, wear-resistant components are needed. They give good service under a very wide range of operating conditions, including continuous temperatures from cryogenic levels to well over 100°C and in a wide variety of situations where resistance to corrosion is needed.

Range of Tufnol Bearing Grades

Our range includes a well-known cotton fabric phenolic bearing grade for lubricated applications, plus two specially developed types with friction-modifying additives.

One potentially useful feature of Tufnol laminated phenolic bearing materials is their ability to be lubricated with water, or with a water-based process fluid. In many applications, this can allow the design to be simplified by eliminating the need for a sealed bearing with oil or grease inside.

Although Tufnol laminates are used dry in a great many less demanding wear applications, Tufnol bearing materials are not generally self-lubricating and it usually is preferable to use a lubricant to develop their full bearing potential. CBM grades are designed to give good performance with minimal lubrication. However, properly designed and lubricated, Tufnol phenolic bearings give excellent service for many years and are frequently a cost-effective choice.