Precision Applied Products Centration Technique for Super Precision Edging

transfer spindle

The Transfer Spindle Method


The process of lens centration performed routinely at Precision Applied Products is based on the “transfer spindle” method.   In the centration process, the spindle that holds the lens element during lens edging is a removable unit, instead of being an integral part of the edging machine.


There are two types of spindles used at Precision Applied Products. The less accurate of the two has a maximum of 1 um (.00004”) full indicator movement (FIM).


The more accurate type of spindles employs class 9 bearings, which have a maximum runout of .5 um (.00002”) FIM.


These spindles have a threaded nosepiece onto which the operator screws an aluminum cup or “chuck” of the size appropriate to hold the lens to be centered.   In order to insure that the chuck is running true, the spindle and chuck are mounted on a small lathe and the spindle is driven on its own bearings while the lens holding surfaces of the chuck are cut true to the spindle axis.


Super Precision Lens Centration


After the lens chuck has been trued to the bearing axis, the spindle is mounted in a centering fixture with its axis vertical. The chuck is warmed by a gas flame so that it can be coated with a low melting wax.   Then, the lens to be centered is pressed against the chuck and rotated under an electronics indicator. The operator pushes the lens in the appropriate direction until the runouts on both the top and bottom surfaces of the lens are reduced to be as precise as .00002”.


The lens and chuck are cooled to set the wax so that the lens is securely held. The spindle is then transferred to the edging machine.   On the edging machine, the lens periphery is edged concentric to its opto-mechanical axis.   Finally, a complete “spark-out” cycle insures that all the residual eccentricities will be eliminated.

In addition, if there is a flat or sag on the lens, this spindle is transferred to a machine for the sag to be cut with the same precision.


Contact us to have your optics processed with this precision technique!!


355-B West Crowther Avenue, Placentia, CA 92870
Ph. (714) 579-7812, Fax (714) 579-7814