Lapping Optical Glass: Optical Glass (CTE 7.1 x 10^-6 /K, 350 nm – 2.0 um); Lapping to flatness 1 – 3 um. Single-piece prototypes to production volumes, quoted from your drawing.
The combination of Optical Glass and Lapping comes up constantly in RFQs for a reason – the material offers striae and stress-birefringence control, and Lapping is the right way to get accurate geometry into it. Expect flatness 1 – 3 um and Ra 0.2 – 0.6 um matte.
The numbers
| Material | Optical Glass (N-BK7, H-K9L and filter glass sets) |
|---|---|
| Thermal expansion (CTE) | 7.1 x 10^-6 /K |
| Service temperature | 400 C (Tg 557 C) |
| Transmission range | 350 nm – 2.0 um |
| Density | 2.51 g/cm3 |
| Knoop hardness | 610 kg/mm2 |
| Refractive index | 1.5168 @ 587 nm |
| Stock thickness | 0.30 – 50 mm |
| Maximum blank size | 300 mm diameter |
| Process | Lapping |
| Working tolerance | flatness 1 – 3 um |
| Minimum feature | thickness +/-0.003 mm |
| Surface finish | Ra 0.2 – 0.6 um matte |
| Thickness window | 0.2 – 40 mm |
| Edge condition | not applicable |
| RFQ inputs | PDF/DXF/STEP drawing, quantity brackets, surface and edge spec |
Getting the drawing right
The shop-floor rules that matter here:
- Material note: index-certified blanks must be oriented and serialized through the shop to keep melt traceability.
- Process boundary: lapped faces are translucent-matte; optical clarity requires a subsequent polish.
- Over-specification is the quiet budget killer: a 20/10 scratch-dig face costs roughly three times an 80/50 face, so grade each surface individually.
For the complete framework, see the tolerance design guide and the holes and edges design guide.
What the process holds
Lapping earns its place through restoring flatness and parallelism on plates and repairing bowed stock. Its boundary condition – lapped faces are translucent-matte; optical clarity requires a subsequent polish – is the first thing our DFM review checks.
Beyond this page, Optical Glass routinely runs through grinding, double-side polishing, coring, edge grinding in our shop – most real parts combine two or three of these steps.
Typical applications
Orders for lapping optical glass cluster in ccd inspection equipment (CCD cover plates, reference grids, stage glass); machine vision (camera windows, ring-light diffusers, calibration plates); scientific instruments (reference flats, cells, prism mounts, stage inserts). Background reading on the underlying material science: RP Photonics: optical glass.
The fastest route to a quote is geometry: use the 3D builder below, draw a dimensioned 2D drawing from it, or open the site-wide custom glass machining 3D + 2D builder for fully custom parts.
Engineers scoping this work usually also review AR optical windows, AR coated glass materials, alkali-free glass wafers.
Buyer questions, answered
What equipment runs the lapping work?
Cast-iron lap plates with boron carbide and alumina slurries.
Is there a minimum order for lapping optical glass?
No. Single prototypes are accepted, and pricing steps down at 10, 100 and 1,000 pieces.
How fast can prototypes ship?
Machined prototypes ship in 5 – 10 working days. Coated or bonded parts add 1 – 2 weeks depending on queue slots.
What files do you need for a quote?
A dimensioned PDF plus DXF or STEP geometry. If only a sketch exists, our drawing review service formalizes it before quoting.
Do parts ship with inspection data?
Dimensional reports, surface certificates and material certs per melt are available; specify the level on the RFQ.
Specifications on this page were last reviewed by our engineering team in September 2026.