ATM : Re : Re ; 12.5" Mirror Figuring

["robert allen" <rallen@iland.net>]

        The best way to reduce an over corrected 12.5" with a 6 inch tool
is to use long strokes. [TOT course]
        The basic concept is to wear away the glass at the .707 zone
of the radius. [square root of 1/2]
        This means the center of the tool must be at the center of the
.707r. SO: .707X6.25 =4.41875 + 3 = 7.41875 - 6.25 = 1.16875" or about
one and 1/6" to one and 1/4" over hang. [both left to right AND both toward
you and away from you] It might be a good idea to actually measure this.
        You can use a small weight at the center of the tool.[one pound
or less] and make your strokes while holding ONLY the edge of the tool.
This should avoid unequal pressure at the edge of the tool. [Bad source
of sleeks] While at the maximum over hang [left and right] your stroke
will be about 3" long while all other strokes will be just long enough to
get
your one and 1/4" over hang.
        Maintain good contact, use slow smooth strokes and be SURE
to work ONLY in complete turns around the mirror.

                Bob Allen A.S.K.C.