Three Precautions in the Operation of the Universal Toolmaker's Microscope
① Pay attention to the focusing sequence of the eyepiece and objective lensMany people start focusing with the objective lens. After focusing on the workpiece, they align it with the crosshair reticle in the eyepiece for measurement. If the crosshair appears blurred, they then adjust the eyepiece. In fact, this sequence is incorrect, as it will create ghost images of the pre-focused workpiece.The correct procedure is to first focus the crosshair reticle in the eyepiece to make it sharp, and then focus the objective lens. This ensures both the crosshair and the image of the workpiece remain clear.
② Pay attention to removing burrs and dents on the workpiece surface before measurementBurrs and dents may form on workpieces during machining, use and transportation. These defects are not easy to detect, but they may cause alignment errors on the universal toolmaker's microscope, or make the measured surface deviate from a single focal plane and form local ghost images, which affects the accuracy of measurement results. Therefore, all surface burrs and dents must be thoroughly removed.
③ Pay attention to the proper mounting of the workpieceThere are two common mounting methods for workpieces on the universal toolmaker's microscope:
(1) Mounting of planar workpiecesFor planar parts, ensure the measured surface lies 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, the image will be out of focus and lead to inaccurate measurement.
(2) Mounting of shaft workpiecesShaft workpieces are generally positioned by their central holes. The central holes must be thoroughly cleaned before installation, especially to remove sediment and burrs. Otherwise, the axis of the workpiece will be misaligned with the central line of the instrument, resulting in large measurement errors. This situation is frequently encountered in routine measurements. A good method is to check the radial runout error of the outer diameter of the shaft workpiece using the horizontal line of the crosshair reticle on the instrument after installation, so as to determine whether the workpiece is mounted correctly.
