Q. Beveling on Curves
In today's small frames, I sometimes have trouble with the curvature of the beveled lenses in high plus prescriptions being different than the curvature of the eyewire. Do I need different frames, or should I do something different with the bevel setting on my edger?

A.
Depending on the equipment you have, changing the bevel setting may be all that is required. The newest three-axis, 3-D finishing systems calculate optimum bevel position by capturing and factoring the frame curvature, the lens curvature, and its thickness. These calculations will at least assure that the bevel remains on the lens, minimizing breakage.

In addition, these controlled bevels will cut down on the need to bend the frame to accommodate the lens.

However, common sense rules still apply. If the frame is of a relatively flat base curve, and has a shallow groove profile. you're better off recommending a different frame.--Michael Urban, Gerber Coburn

Q. Direct, or Recycled?
When using an automatic edger, what's the difference between using a direct water hook-up and using a re-circulating system?

A.
There are basically three reasons why it's better to go with a direct water hook-up:

1) It's better for the edger itself because it is always receiving clean water. There is less maintenance involved.

2) It's better for the lenses because it's clear water vs. purified water going on the lenses. Even though the recirculated water is pretty clean, you can't be sure it's as clean as the water from the direct water hook-up.

3) It's easier for the operators, because they don't have to change the water in the tank and pump.--Rick Noonkester, Santinelli International

Q. Polarized Progressives
Although I have an up-to-date edger with an LCD display, I have a difficult time identifying the markings and the location of the optical center and cross on polarized progressive lenses. Sending them out all the time is getting expensive. Any suggestions?

A.
Due to the darkness of the lens, it is indeed a bit more difficult to see the markings. You have to over-compensate by marking the optical center with a heavier cross than usual, using a very dark black marker.

Also, each manufacturer puts a set of arrows on the ends of the 180-degree line -- both on the right and left sides. By using these lines as a guide, you'll ensure that you stay on center and keep the lens in the correct position.--Bill Galindo, President, ODl

Q. High Base Curves
Although I have been generating my own jobs for some time, I always send jobs with higher base curves out for processing. I recently upgraded to a 3-axis generator and understand I can tackle these jobs in-house. can you tell me how to successfully surface the backside of lenses when the base and cross curves are a minus 11 or more?

A.
A 3-axis generator greatly extends your capabilities to process jobs in a wider range of powers and gives you the ability to cut your own lap tools in approximately five minutes -- resulting in significant cost and time savings.

Follow these steps to ensure success:

1. Begin by making sure you always choose the proper base curve. If the power is above a minus 11, you might want to consider using a minus front base curve.

2. When the base curve is a minus 11 or higher, you will need to cut a "high-hat" lap tool that will match the curves specifically. This type of tool will have the smaller diameter and a steeper curve needed to process a high-minus job. To produce a "high-hat" lap tool, begin with raw lap blanks from any manufacturer.

3. Using the raw lap blank, cut the lap and verify the curves with a sag gauge. The tolerance should be plus or minus .02 of sag value.

4. Perform the calculations and data entry, and then cut your lenses in the usual manner.--Stuart Watson, National Optronics EB

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