Surface Abrading

In preparation for gage installation, the surface is abraded to remove any loosely bonded adherents (scale, rust, paint, galvanized coatings, oxides, etc.), and to develop a surface texture suitable for bonding. The abrading operation can be performed in a variety of ways, depending upon the initial condition of the surface and the desired finish for gage installation. For rough or coarse surfaces, it may be necessary to start with a grinder, disc sander, or file. ( Note : Before performing any abrading operations, see safety precautions .) Finish abrading is done with silicon carbide paper of the appropriate grit, and recommended grit sizes for specific materials are given in the Index of Test Materials and Surface Preparation Procedures .

If grit-blasting is used instead of abrading, either clean alumina or silica (100 to 400 grit) is satisfactory. In any case, the air supply should be well filtered to remove oil and other contaminant vapors coming from the air compressor. The grit used in blasting should not be recycled or used again in surface preparation for bonding strain gages.

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