mesuring a sag

[mahmoud.hamza]

Hi
have you an idea how to mesur exactelly a sag of the front base of a semi finished lens !!
I used a torometer but every time the result is not exact!! and for the freeform progressive we need an exact power of the front curve !
thx

[DocInChina]

Hi
have you an idea how to mesur exactelly a sag of the front base of a semi finished lens !!
I used a torometer but every time the result is not exact!! and for the freeform progressive we need an exact power of the front curve !
thx

Do you have a sag gauge? If not you could use a lens clock and convert the Dioptor to radius and then to sag.

[mahmoud.hamza]

Do you have a sag gauge? If not you could use a lens clock and convert the Dioptor to radius and then to sag.

Iam using a torometer but the result is not every time Ok

[KStraker]

We use a Coburn Sagmate, digital sagometer. The results can vary slightly from lens to lens. A 6BC SV usually measures 3.75. Sometimes they come in at 3.73 or 3.74. If you are sagging a FT lens, be sure you have the seg in the right spot and that the base of the lens is flat against the measuring rod.

[mahmoud.hamza]

If you are sagging a FT lens, be sure you have the seg in the right spot and that the base of the lens is flat against the measuring rod.

can you please explaine
we also we use a cubern one and the value that we found are not stabel
because the cubern sag meter is manual and some times the angel between the lens and the sagmeter is not the same

[KStraker]

can you please explaine
we also we use a cubern one and the value that we found are not stabel
because the cubern sag meter is manual and some times the angel between the lens and the sagmeter is not the same

There's a cup on the bottom where you press the lens. It has a notched out area where the seg should go. It should be facing you. Make sure you do not press the seg area against the measuring rod. Press the lens flat against the bottom plate and be sure that the measuring rod is on the base curve of the lens and not on the segmented portion. Obviously the seg will have a steeper curve. Be sure to recalibrate the sag meter before you use it. (use the flat metal block) I have some AO and Silor FT on hand if you want to compare. I have couple VE and Sola also.