When refinishing the drum, remove only enough metal to obtain a true, smooth braking surface. Replace the drum if it does not clean up when refinished to a maximum refinish diameter, as directed in the Specifications. Removal of more metal will affect the heat dissipation and may cause a drum distortion.
The brake drums have a maximum diameter cast into them. This is the maximum wear diameter not a refinish diameter. Do not refinish a drum which does not meet the Specifications. Replace the drum if this occurs.
When refinishing a brake drum, resurface the drum to a dimension no more than 0.76 mm (0.030 in) less than the discard diameter. The refinish diameter is the maximum diameter to which the drum may be refinished and still provide safe braking. If the dimension is exceeded, the drum will wear beyond the discard diameter during normal brake wear.
Always use sharp cutting tools or bits. Use only replacement cutting bits recommended by the equipment manufacturer. Dull or worn tools leave a poor surface finish which will affect the initial braking performance.
Always use vibration dampening attachments to prevent tool chatter and a better surface can be obtained.
When refinishing a brake drum, the following is recommended:
| • | Optimum spindle speed: 200 rpm. |
| • | Cross feed (per rev): |
| - | Rough cut, 0.25 to 0.15 mm (0.010 to 0.006 in). |
| - | Finish cuts 0.05 mm (0.002 in), maximum. |
