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How Deep Is An Inner Rim Nylor Groove?

An inner rim nylor groove is commonly cut at about 0.4 to 0.5 mm deep for nylon-cord or semi-rimless eyewear, based on ophthalmic lens-finishing guidance. Some frame technical specs use a slightly deeper 0.6 mm groove for T-rim or nylor designs, with a groove width of at least 0.8 mm, so the exact cut depends on the frame and cord system. The groove only needs to be deep enough to seat the nylon cord securely around the lens edge, not so deep that it weakens the lens. Optical finishing guidance also points to edge thickness as part of the fit, with one training handout listing 2.2 mm as a minimum edge thickness for groove, rimless, or nylor work. If the groove is too shallow, the cord can slip; if it's too deep, the lens edge can become more prone to chipping or poor support.

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How Deep Is An Inner Rim Nylor Groove?

An inner rim nylor groove is commonly cut at about 0.4 to 0.5 mm deep for nylon-cord or semi-rimless eyewear, based on ophthalmic lens-finishing guidance. Some frame technical specs use a slightly deeper 0.6 mm groove for T-rim or nylor designs, with a groove width of at least 0.8 mm, so the exact cut depends on the frame and cord system. The groove only needs to be deep enough to seat the nylon cord securely around the lens edge, not so deep that it weakens the lens. Optical finishing guidance also points to edge thickness as part of the fit, with one training handout listing 2.2 mm as a minimum edge thickness for groove, rimless, or nylor work. If the groove is too shallow, the cord can slip; if it's too deep, the lens edge can become more prone to chipping or poor support.

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Why Groove Depth Affects Lens Security

Groove depth affects lens security since the nylon cord needs enough channel space to sit firmly around the lens edge. In semi-rimless frames, the cord runs along the outer lens edge and fits into the groove, so a shallow cut can leave the cord poorly seated. Optical edger specs show groove depth can be adjusted from about 0.20 mm to 1.20 mm, with groove width from about 0.55 mm to 1.20 mm, depending on the frame and lens setup. The lens also needs enough edge thickness for grooving, since thinner edges are more prone to chipping where the frame does not fully protect the lens.

What Lens Thickness Works Best For A Nylor Groove

For a nylor groove, the safer target is a finished lens edge thick enough to hold the groove without making the edge fragile. A Vision Expo lens-finishing handout lists 2.2 mm minimum edge thickness for groove, rimless, or nylor work, compared with 1.3 mm for standard full-rim bevels and 1.7 mm for drilled lenses. Older optical processing guidance gives 1.5 mm as an absolute minimum, but notes that going thinner can weaken the grooved or drilled edge and raise the risk of chipping. In practical terms, 2.2 mm or thicker is the cleaner benchmark for a nylor groove, especially when the lens material, prescription strength, and frame shape leave less edge support.

How Nylon Cord Holds Semi-Rimless Lenses In Place

A nylon cord holds semi-rimless lenses by sitting inside a small groove cut around the lens edge, then pulling the exposed side of the lens snugly against the frame. The cord acts like a hidden retaining line, and one optical supply listing shows round semi-rimless cord at about 0.5 mm, which gives a sense of how fine the material can be. The groove has to match the cord closely, since a loose fit can let the lens shift while a tight or poorly cut groove can stress the lens edge. Lens thickness also matters here, since semi-rimless lenses need enough edge strength to handle grooving without chipping or breaking.

What Opticians Check Before Cutting A Nylor Groove

Before cutting a nylor groove, opticians check whether the frame, lens material, prescription, and finished edge thickness can handle semi-rimless mounting. Lens-finishing guidance warns that a semi-rimless lens needs enough edge thickness because the groove and exposed edge can chip if the lens is too thin. Trade guidance gives 1.5 mm as an absolute minimum edge thickness, with 2.0 to 2.2 mm often planned for plus lenses that need more support. Opticians also check the frame trace or demo lens shape, since poor tracing can affect lens sizing and how well the nylon cord sits in the groove. After finishing, the glasses are inspected against the prescription and fitting measurements before delivery.

Frequently Asked Questions About Inner Rim Nylor Groove

Is an inner rim nylor groove the same as a bevel?

No. A bevel helps a lens sit inside a full frame rim, while an inner rim nylor groove is a narrow channel cut around the lens edge so a nylon cord can hold a semi-rimless lens in place.

Can an inner rim nylor groove work with high-index lenses?

Yes, but the finished edge still needs enough thickness to hold the groove safely. Optical trade guidance lists 1.5 mm as an absolute minimum edge thickness, with 2.0 to 2.2 mm planned for some plus lenses that need more support.

Can you replace lenses in frames with a nylor groove?

Yes, many semi-rimless or nylor frames can be relensed if the frame is stable and the nylon line is not stretched, frayed, or brittle. The new lenses still need accurate edging and grooving so the cord can hold them securely.

Does an inner rim nylor groove make the lens more fragile?

It can if the groove is cut too close to the lens edge or the remaining lens wall becomes too thin. Lab finishing guidance notes that a groove around 0.5 mm wide and 0.4 to 0.5 mm deep needs to follow the lens contour closely to avoid weak points near the edge.

References

Eight Tips for Processing Rimless or Semi-Rimless Eyewear. EyeCare Business. https://eyecarebusiness.com/issues/1999/august/eight-tips-for-processing-rimless-or-semi-rimless-eyewear/. Published August 1, 1999. Accessed May 22, 2026.

Making the Perfect Match. Jesse Walters, ABOM, Vision Expo West. https://www.visionexpo.com/content/dam/sitebuilder/rna/vision-expo-west/2024/docs/courses/course-handouts/35O4-Frame-and-Lens-Making-a-Perfect-Match.pdf.coredownload.224461472.pdf. Published date not listed. Accessed May 22, 2026.

Mr. Orange M22 User Manual. Essilor Instruments USA. https://www.essilorinstrumentsusa.com/wp-content/uploads/2018/08/Mr.-Orange-M22-User-Manual-US.pdf. Published date not listed. Accessed May 22, 2026.

Nylon Rimless Cord, Round. SIOS Optical. https://siosoptical.com/products/nylon-rimless-cord-round/. Published date not listed. Accessed May 22, 2026.

Optical Dispensing Chapter 5. Aurosiksha. https://www.aurosiksha.org/public/lica/assets/pdf/optical-dispensing.pdf. Published date not listed. Accessed May 22, 2026.

The Eyecare Provider's Basic Dispensing Guide. The Vision Council. https://thevisioncouncil.org/sites/default/files/assets/media/Dispensing-Guide_2020.pdf. Published 2020. Accessed May 22, 2026.

The Parts of Glasses: Names & Phrases. Banton Frameworks. https://www.bantonframeworks.co.uk/blogs/manufacture/parts-of-glasses. Published January 13, 2021. Accessed May 22, 2026.