Precautions for Operating the Universal Toolmaker's Microscope
① Focusing Sequence of Eyepiece and Objective Lens Many people prefer to start focusing with the objective lens. After focusing on the workpiece, they align the workpiece with the crosshair reticle. If the crosshair looks blurred at this point, they adjust the eyepiece. In fact, this sequence is incorrect. This approach will produce ghost images of the focused workpiece on the front surface. The correct procedure is to first focus the crosshair of the eyepiece, and then focus the objective lens. In this way, both the crosshair and the workpiece image can remain sharp.
② Remove Burrs and Dents on the Workpiece Surface before Measurement Workpieces may develop burrs and dents during machining, use and transportation. These defects are often hard to detect, but they may easily cause misalignment during measurement or make the measured surface lie outside a uniform focal plane, forming local ghost images and impairing measurement accuracy. Therefore, all surface burrs and dents must be thoroughly removed.
③ Proper Mounting of the Workpiece There are two common mounting types for workpieces on the universal toolmaker's microscope: (1) Mounting of planar workpieces The measured surfaces of planar workpieces should lie on the same focal plane; otherwise, local ghost images will easily form. For parts with chamfers on the measured surface, it is best to place the chamfer facing downward. Otherwise, unfocused images may occur and lead to inaccurate measurement results.
(2) Mounting of shaft workpieces Shaft workpieces are generally positioned by the central hole. Therefore, the central hole must be thoroughly cleaned before mounting, especially to remove sediment and burrs. Otherwise, the axis of the workpiece will be misaligned with the instrument's central line, which will cause large measurement errors. A good solution is to check the radial runout error of the shaft outer diameter using the horizontal line of the crosshair reticle on the instrument after mounting, so as to judge whether the workpiece is properly installed.
