Jan
2003

L&T 101: On the Edge

Dispensers offer insights into one of optical’s few remaining “arts”—hand-edging

By Brian P. Dunleavy


Here, in the age of computerized patternless edgers, the task of hand-edging recalls the days when opticians were true craftsmen. But it is by no means an outmoded function of today’s in-office finishing labs.

Indeed, the vast majority of lenses finished in-office today still require the use of a hand edger (which is also often referred to as a handstone or touchstone) for touch-up work as well as some beveling work, even when high-tech patternless edgers offer—or at least promise—users similar functions. But experienced opticians emphasize that though these relatively old-fashioned machines remain in wide use in optical shops, it doesn’t necessarily mean the machines are still used wisely.

“Years ago, we used the handstone to produce lenses with sophisticated shapes—things like heart or octagon shapes—that we would then put into rimless mounts,” notes Jim Murray, optician and owner of Lawrenceville Opticians in Lawrenceville, N.J. Murray has been an optician for more than 30 years.

“That’s a lost art,” he continues. “Opticians new to the field can operate the handstone, but they can’t do any of that refined stuff. It takes a lot of practice just to learn some of the basic touch-up work.”

These days, handstones are used primarily for tasks such as “hiding a bevel,” which involves “rounding off the bevel” so the lens isn’t as visible “behind the eyewires of the frame,” according to James Britton, the lab technician/optician for Contact Lens Associates in Albuquerque, N.M. They are also used for other touch-up work and for re-sizing a lens when patients want to change their frame. Some experienced opticians/lab techs still do all of their safety beveling work on the handstone. Safety beveling involves rounding off the exposed edge of the lens so it doesn’t cut the wearer.

“Even with the accuracy of our patternless edger, which has a safety-beveling cycle, I still prefer to safety bevel or touch-up using the handstone,” explains Melody Fisher, the lab technician at Newman, Blackstock & Associates, a nine-office optometric practice in Roanoke, Va. “With the growth in drilled rimless frames and thin lens materials, lens edges are sharper and more exposed than ever.”

So what does a newcomer to hand-edging need to know? Whether you are a young optician or lab tech, or an optical/lab manager training new staff, there are some basics everyone needs to know before they can handle this very important task. One advantage new opticians have in hand-edging is that the technology involved hasn’t changed fundamentally in the past 30 or 40 years. Hand-edgers or handstones remain essentially an electrically powered grinding wheel that can be run wet (with water delivered via a hose near the wheel) or dry. Today, though, most handstones use diamond wheels, which are easier to maintain and keep clean, instead of the older ceramic wheels. Some say diamond wheels also provide a smoother cut.

Newer machines are also equipped with water pumps to keep the supply constant so operators don’t have to keep re-filling the tray between cycles. Handstones range in price from $500 to $2500, depending on the make and model. In smaller, retail-level labs, the handstone should be placed between the edger and the mounting area for ideal workflow. After all, hand-edging encompasses the processing steps required between finishing the lens and mounting it into the frame.

One of the most important skills needed in hand-edging is “touch.” Operators need to know the amount of pressure to place on the lens and wheel in order to accomplish the desired task. The amount of pressure differs by lens shape and material. Too much pressure can cause the wheel to cut too far into the lens, moving the bevel, ruining the edge or even compromising the shape. Too little pressure, of course, and you are not getting the desired cut.

The only way to acquire or develop “touch” is through trial and error, veteran dispensers say. Some suggest practicing hand-edging on previously used lenses or lenses “spoiled” in other parts of the finishing process. “Make use of those lenses you’d otherwise be throwing away,” says Britton. “Hand-edging is done by feel. You have to know how much pressure a lens can take.” Britton also stresses the importance of holding the lens firmly during hand edging. “If it slips, the wheel could scratch, and therefore spoil, the lens,” he adds.

Once you have started to hand-edge a lens, you should finish the job in one cycle. “Don’t keep starting and stopping or pulling the lens away from the wheel,” Fisher cautions. “You’ll forget where you’ve left off and miss a spot. Also, follow the shape and contour of the lens shape. Don’t alter the shape of the lens on the handstone unless you are re-sizing the lens.”

In terms of working with specific jobs, hand-edging do’s and don’ts vary from lens to lens. With glass lenses, for instance, “touch” is particularly important. Too much pressure on the edge of a glass lens can cause the lens to chip, spoiling the lens and, sometimes, clogging up the handstone. With polycarbonate, most opticians/lab techs hand-edge dry. Because of the material’s soft nature, wet-cut edging poly can be messy because of the additional swarf (handstone wheels, by the way, must be kept clean for optimum cutting). But Murray, who believes in “running every lens wet when beveling,” suggests hand-edging poly wet, just with a reduced water supply. He feels the wet wheel provides a smoother, more accurate cut.
Finally, Britton, who dispenses a significant amount of polarized lenses at his location, warns against placing the groove too close to the back of a polarized lens when hand-edging. “With the groove close to the back, the wearer can almost see around the polarized filter,” he says. “They’ll almost see a white spot once the lens is fit into the frame.

“It takes time to learn little details like this,” he continues. “But once you’ve got it, hand edging is actually pretty easy.”

 

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