Brands
Vishay Measurements Group
Interactive Guide
Instruments
RS-200 System
RS-200 Milling Guide
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Residual Stress Measurements
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RS-200 Milling Guide
The RS-200 Milling Guide is a precision fixture for accurate positioning and drilling of a hole through the center of a special strain gage rosette. Principal features and components of the milling guide assembly are shown in the photos below. When installed on the workpiece, the guide is supported by three leveling screws footed with swivel mounting pads to facilitate attachment to uneven surfaces. 
Alignment of the milling guide relative to the strain gage rosette is accomplished by inserting a special-purpose microscope into the guide's centering journal, and then positioning the guide precisely over the center of the rosette by means of four X-Y adjusting screws. The microscope assembly, consisting of a polished steel housing with eyepiece, reticle, and objective lens, permits alignment to within 0.0015 in (0.038 mm) of the gage center. The microscope is also used to measure the diameter of the hole after it is drilled. An illuminator attaches to the base of the guide to aid in the optical alignment procedure. 
After alignment, the microscope is removed from the guide, and the milling bar or high-speed air turbine is inserted in its place. The milling bar is used for slow-speed drilling of the hole. Two standard milling cutters are supplied: 0.062 and 0. 1 25 in (1. 6 and 3.2 mm) diameter. The milling bar is equipped with a universal joint for flexible connection to a drill motor. 
Conventional slow-speed milling may be satisfactory on some mild steels and aluminum alloys. But high-speed drilling is generally the most convenient and practical method for introducing the hole in all test materials. (When residual stresses are to be measured on materials such as stainless steels, nickel-based alloys, etc., ultrahigh-speed drilling techniques are preferred.) For this purpose, a high-speed air-turbine assembly, along with a supply of tungsten carbide-tipped cutters [ten each 0.031 in (0.8 mm) diameter and 0.062 in (1.6 mm) diameter], is supplied with the milling guide. A foot pedal control is included for operating the air turbine. 
A micrometer depth set attachment, available in English or metric units, is provided with each milling guide assembly. This device is used for incremental drilling when information on the variation of residual-stress-with-depth is desired. Other items supplied include a plastic template for the proper location of the milling guide foot pads on the test part and a special break-off tool used to remove the foot pads from the part after the test is completed. All components are housed in a sturdy carrying case. The guide is approximately 9 in (230 mm) high, and 4.5 in (1 14 mm) wide at the base. A fast-setting-cement kit, used to firmly attach the guide to the test part, is available as an accessory item. 
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