Correct nylor thickness

[mauroventura]

Hello guys.
I was recently involved in a discussion with some customers concerning the calculation of the lens thickness needed to edge for a nylor frame.
my rule is :
if we speak about cr39 and resins hi:
avoid stock lenses and when you start to calculate To build the lens,add 1 mm to mininmum edge thickness for a positive or center thick for a negative one.
do i want to work too much in safe mode?

[scriptfiller]

If it's a CR-39 I like a 2.5mm minimum edge thickness. I like to have at least 1mm of material on either side of the groove. A 2.0mm minimum edge on all MR series lenses as well as poly and Trivex. Using stock lenses is kinda of a cr@p shoot.

[gemstone]

Hello guys.
I was recently involved in a discussion with some customers concerning the calculation of the lens thickness needed to edge for a nylor frame.
my rule is :
if we speak about cr39 and resins hi:
avoid stock lenses and when you start to calculate To build the lens,add 1 mm to mininmum edge thickness for a positive or center thick for a negative one.
do i want to work too much in safe mode?

Your positive lenses will be too thick. Also it's not necessary to add to all negative lenses. Only the very weak thin ones ( many weak power Resolutions, for example will be too thin.)

[hipoptical]

You're playing too safe. The minimum for any lens is really 2.2mm edge. It's not necessarily the best thickness, but it really is the minimum for any material. Using stock lenses is fine when you know that the finished edge will be at least 2.2mm, but I think scriptfiller is right in that 2.5mm is better.

[Memoir]

I would speak to your lens caster. They will have their own recommendations for their own materials in regards to minimum edge thickness for all frame types!

For an example, Hoya recommend:

Nylon, In-line Metal and 3 Piece Rimless respectively

1.49 - 2.2, not recommended, not recommended

1.53 - 1.7, 2.2, 1.7

1.55 - 2.2, not recommended, not recommended

1.60 - 1.7, 2.2, 1.7

1.67 - 1.7, 2.2, 1.7

1.71 - 1.7, 2.2, 1.7


Regards,
Memoir.

[Murray O'Brien]

I think Memoir's recommendations from Hoya are pretty right. With trivex, can go a little thinner than 1.7mm if you're grooving setup is spot on. I am a bit surprised that they would do a job in 1.55 for a nylon at all though. That stuff is seriously brittle! About time to stop doing it in CR39 as well!

[sherbet]

You're playing too safe. The minimum for any lens is really 2.2mm edge. It's not necessarily the best thickness, but it really is the minimum for any material. Using stock lenses is fine when you know that the finished edge will be at least 2.2mm, but I think scriptfiller is right in that 2.5mm is better.

I agree with hipoptical, we always make lenses 2.2mm for Nylon frames. Lenses need to be thicker for inline metal 2.8mm at least (depends on thickness of frame). The Hoya recommendations seem a bit thin.