<title>Suitability of igneous rock for precision tooling</title>

Abstract

Surface plates and blocking tools are commonly made of granite because of its good stability. But how stable is the granite, and which type of material is optimal? We have explored several materials and manufacturing processes for a 4-m aspheric reference surface that would serve as a tool for laying up composite optics. In this paper, we discuss the materials selection, stability to thermal and moisture effects, and parameters for processing the surface to give sub-micron accuracy and stability.

Influences of Moisture Expansion on Motion Errors of Granite Hydrostatic Guideways

“…Because the quartz is harder than the surrounding minerals in granite, pocket boundaris are created as the rock settles over time, so there are some pores for moisture absorption. The higher the quartz content is, the more obvious the moisture effect will be [8,9]. Based on such a property of the granite, it was speculated that the moisture expansion would influence the stability of the geometric accuracy and structural dimensions when the granite guideways work in a moist environment [10,11].…”