Field tests on rolling-cutt er boring bits with journal bearings made of composite materials

Conclusions

• 1. Composite materials containing wear-resistant grains evenly distributed in ductile matrices possessing solid lubricant qualities can be successfully used for bearings of rolling-cutter boring bits.

• 2. Tests carried out on experimental bits with sliding bearings made of composite materials have shown that, compared with standard types, such bits double the sinking length and at the same time increase the maximum mechanical drilling speed.

• 3. A rolling-cutter bearing with two pressed-in sliding bearing elements gives satisfactory performance.

• 4. The sealing unit and the system of lubricant supply and lubricant pressure equalization in type 2AN269, 9SZG boring bits must be redesigned and the load distribution on the journals in these bits made more uniform.

• 5. Work should continue with the aim of formulating even more successful composite materials for journal bearings of rolling-cutter boring bits and devising improved methods for facing bearing elements with these materials.