Manual Blocking of Flatop Blanks

[Prads1969]

This might seem like a silly question in this day and age with the new CNC blockers out there. But i wanted to know how one would mark and block the axis of a Flat top Bifocal manually prior to conventional surfacing. Thank you in advance

[dima]

Hi, I hope this can be helpfull for you:

Round and Blended Bifocal Centration and Blocking - YouTube

[Lensman11]

To mark a ft first are you on center blocking or oc center blocking. For on center you need to know or actually measure the set location in the blank. If it is 5 below and 5 in then you draw a line parallel to seg 5 above the seg line with vertical cross half way between the diameter of the lens. This is if you blocking on the 180 of you are blocking on cylinder axis then the line that was parallel to the seg has to at the cyl axis you will need a protractor to do this. If you blocking on oc then you have to put a dot at the piston of the desired location if the oc and follow the prevois directions.