SLIP GAUGE

Slip gauges or gauge blocks are used as standards for precision length measurement. These are made in sets and consist of a number of hardened blocks, made of high grade steel with very low thermal expansion. They are hardened throughout, and heat treated further for stabilization. The two opposite measuring faces of each block are lapped flat and parallel to a definite size within extremely close tolerances. A particular size can be built up by wringing individual slip gauges together. Wringing is the act of joining the slip gauges together while building up to sizes. Some sets of slip gauges also contain protector slips made to standard thicknesses from higher wear-resistant steel or tungsten carbide. These are used for protecting the exposed faces of the slip gauge pack from damage while in use. GRADES The following four grades of slip gauges are recom- mended as per IS 2984-1981 Grade '00', Grade '0', Grade '1' & Grade '2' Grade '00' shall normally be used for calibration purposes. It shall not be used in combination. Grades 0,1, and 2 are intended for general use. Grade'0' is used only for calibration of Inspection Grade '1'. Grade '1' is used in tool room and standards room. It is also used for calibration of Grade '2'. Grade '2' is used on machines for setting purposes and on surface plate for inspection purposes in shop floor. It is also used for zero setting of precision measuring instruments in shop floor. For further details refer IS 2984-1981. B.I.S. recommendations Three grades of slip gauges are recommended as per IS -2984. They are: Grade '00' Grade '0' Grade '1' Grade '2'. Care and maintenance points to be remembered while using slip gauges Avoid handling the slip gauges with bear hands, since this affects the size of them due to heating. Use a minimum number of blocks as far as possible while building up a particular dimension. - While building the slip gauges, start wringing with the largest slip gauges and finish with the smallest. While holding the slip gauges do not touch the lapped surfaces. If available use protector slips on exposed faces. After use, clean the slips with carbon tetrachloride and apply petroleum jelly for protection against rust. Before use, remove the petroleum jelly with carbon tetrachloride. Use chamois leather to wipe the lapped surfaces.