How to Make Glasses With CNC Machine

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  Key takeaways
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  What You Need Before You Make Glasses With CNC Machine
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  Material Choice: Titanium, Stainless, Aluminum, or Acetate
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  Roughing and Finishing the Front and Temples
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  Hinge Pockets, Screw Threads, and Lens Fits
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  Step by Step: How to Make Glasses With CNC Machine
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  Which Process Fits Which Frame

Eyewear is a small part with a long list of requirements. A frame has to hold a lens to a tenth of a millimeter, survive being sat on, and look clean under a jeweler's loupe. That combination is why machine shops treat eyewear differently from brackets or housings.

The first decision is the front. Metal fronts are usually milled from a single billet, then the eyewire groove is cut in a second operation. Acetate fronts are milled from sheet or block, then polished. Both routes use the same machine, but the fixtures and the feed rates are not close.

The second decision is size. A front blank for a standard frame fits inside 150 × 60 × 12 mm, which is small work for a 5-axis center. The temples are longer, up to 150 mm, and they are thin. Thin, long parts move. That is the whole problem in one sentence.

Before cutting anything, confirm four things: the CAD is watertight, the lens curve is defined, the hinge is a real catalog part or a fully dimensioned drawing, and you know which surface will be visible. Visible surfaces need a finishing pass that a hidden boss does not.

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  Lens curve firstThe eyewire groove profile follows the base curve, not the other way around.
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  Hinge sourceUse a catalog hinge or dimension the barrel and screw pitch in the drawing.
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  Visibility mapMark which faces show after assembly so the toolpath can leave them clean.
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  Blank allowanceLeave 0.3–0.5 mm on thin rims for a spring pass and finishing.

Titanium is the default for premium metal frames because of strength-to-weight. TC4 (Ti-6Al-4V) machines at 40–60 m/min surface speed with carbide tooling and high-pressure flood coolant. Climb milling keeps the cut on the edge, not on the flank. If the tool rubs, the surface work-hardens within a few passes and the next pass chips.

Stainless 316L is easier to cut and cheaper, but it is heavier. It takes a bright polish well and suits frames that will be sold on finish rather than weight. 17-4PH (SUS630) gives more spring in the temple arms and can be heat treated if the design needs it.

Aluminum 6061-T6 is common for prototypes and for frames that will be anodized. It cuts fast, holds ±0.005 mm without drama, and accepts clear, color, hardcoat, and conductive anodizing. The trade-off is stiffness. A 1.0 mm aluminum temple bends more than the same temple in titanium.

Acetate, PMMA, and PEI (Ultem) are machined with two-flute or single-flute cutters at 12,000–18,000 rpm. Acetate wants sharp tools and air blast, not coolant, because coolant clouds the surface. Leave 0.2 mm for a finishing pass and expect a polishing step afterward. PEEK and carbon fiber are options for industrial eyewear and safety frames.

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  Titanium TC440–60 m/min, flood coolant, climb milling, expect longer cycle time.
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  Stainless 316L60–90 m/min, good polish response, higher weight.
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  Aluminum 6061-T6200–400 m/min, best for anodized prototype frames.
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  Acetate12,000–18,000 rpm, sharp single-flute, air blast, polish after.

Rough the front with a Ø6 mm or Ø8 mm three-flute end mill, leaving 0.4 mm of stock on all surfaces. Use adaptive or trochoidal paths on titanium and stainless so the radial engagement stays low and the heat leaves with the chip. On aluminum you can push radial engagement higher and finish in fewer passes.

The eyewire groove is the operation that fails most often. A 0.8–1.2 mm grooving cutter at 0.05–0.10 mm per pass, with a spring pass at the end, holds the lens seat without chatter. Support the rim from below with a fitted soft jaw or a machined pocket. Unsupported rims ring like a tuning fork and the groove wall goes wavy.

Temples are long and thin, so cut them from bar stock in a fixture that supports the full length, or leave a sacrificial web and cut it off last. Deflection grows with the cube of the unsupported length, so a 100 mm overhang and a 60 mm overhang are not the same job.

Finishing strategy matters for appearance. A ball-nose pass with 0.05–0.10 mm stepover gives a surface around Ra 0.8–1.6 μm on metal, which is a good base for bead blasting or brushing. Where the frame will be polished, leave the tool marks shallow and consistent so the polisher is not chasing deep gouges.

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  Roughing stock0.4 mm radial and axial on titanium and stainless.
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  Groove passes0.05–0.10 mm per pass plus a spring pass at the end.
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  Temple supportFull-length fixture or sacrificial web, never free overhang.
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  Finishing surfaceRa 0.8–1.6 μm before blasting or polishing.

A hinge is a small precision assembly, and it is usually what makes a frame feel cheap or expensive. The barrel bore for a standard hinge screw runs 1.4–1.6 mm depending on the screw spec. Drill it undersize, ream to size, and check the fit with a pin gauge, not by eye.

The hinge pocket in the temple has to align with the pocket in the front. If the two pockets are cut in separate setups without a common datum, the temple will sit high or low when the screw goes in. Cut both mating surfaces from the same reference face, or use a matched pair fixture.

Threads on 2.0 mm and smaller screws are a cutting tap job, not a forming tap job, in titanium and stainless. Use a tapping fluid rated for the alloy and peck the tap to clear chips. Broken taps in a finished frame mean the frame is scrap.

Lens fits are a snapshot fit. The eyewire groove is cut to the lens edge profile with 0.05–0.10 mm clearance, and a nylon or silicone cord fills the gap on metal frames. Cut the groove too tight and the lens chips during insertion. Too loose and the lens rattles.

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  Hinge bore1.4–1.6 mm, drill undersize then ream to size.
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  Common datumCut front and temple pockets from one reference face.
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  Small threadsCutting taps with alloy-rated fluid, peck to clear chips.
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  Lens clearance0.05–0.10 mm in the groove, cord or gasket to fill it.