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Designed for accurate measurements on plastic and glass lenses. Perfect plus or minus curve measurements in quarter diopters on either front or back of any lens in .25 diopter increments. Genuine clock movement with ball tips will not scratch lenses.
HOW TO CALIBRATE A LENS CLOCK
Calibration of a lens clock is part of its regular maintenance. Duration of calibration depends on roughness of handling on a daily basis. Steps: Remove black pin protective cover, Insert screwdriver at the top of the clock as at 12:00 & flip off the face plate, Using the fingers pull off the needle. The needle is positioned over a stem with 2 grooves. How stiff the needle is to remove depends on which groove the needle is set on. The needle will generally come off with a degree of ease. If the needle is stubborn, use a screwdriver gently to pry off. USE caution the needle tends to “ fly” away. Hold the clock in one hand & gently depress the pins at the top evenly against the metal surface. With the pins depressed, replace the needle with the other hand on the stem at the zero setting. After setting the needle, test the clock by pulling away & the pressing again against the metal surface. Many times it is necessary to make minor fine adjustments a couple more times. When the needle has returned to zero 3 times, push the needle a little harder on the stem and test once again. If still at zero, the clock is calibrated. Replace the face plate.
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