Grinding Optical Glass – Optical Glass (CTE 7.1 x 10^-6 /K, 350 nm – 2.0 um); Grinding to flatness to 5 um over 100 mm. No minimum order; DFM review included with every RFQ.
grinding optical glass is a materials problem before it is a machining problem. Optical Glass has certified refractive index and dispersion and a Knoop hardness of 610 kg/mm2, so the grinding recipe – feeds, coolant, tooling – differs from what works on ordinary float glass. The line runs rotary surface grinders and double-disc machines with diamond wheels and holds flatness to 5 um over 100 mm.
Key parameters
| 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 | Grinding |
| Working tolerance | flatness to 5 um over 100 mm |
| Minimum feature | thickness to +/-0.005 mm |
| Surface finish | Ra 0.2 – 0.8 um |
| Thickness window | 0.3 – 60 mm |
| Edge condition | ground perimeter, squareness 0.02 mm |
| RFQ inputs | PDF/DXF/STEP drawing, quantity brackets, surface and edge spec |
Specification advice
Before sending the RFQ, check these against your drawing:
- Material note: index-certified blanks must be oriented and serialized through the shop to keep melt traceability.
- Process boundary: subsurface damage of 5 – 15 um must be budgeted and removed by polishing on optical faces.
- 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
Grinding earns its place through bringing thickness, flatness and parallelism into calibrated tolerance before polish. Its boundary condition – subsurface damage of 5 – 15 um must be budgeted and removed by polishing on optical faces – is the first thing our DFM review checks.
Beyond this page, Optical Glass routinely runs through ultrasonic machining, edge grinding, lapping, cnc machining in our shop – most real parts combine two or three of these steps.
Application context
Orders for grinding optical glass cluster in ccd inspection equipment (CCD cover plates, reference grids, stage glass); optical sensors (sensor windows, filter caps, lens covers); machine vision (camera windows, ring-light diffusers, calibration plates). Background reading on the underlying material science: RP Photonics: optical glass.
Dimensions still moving? Configure this part live in the 3D builder below, or open the full custom glass machining 3D builder to start from a blank canvas.
For adjacent specifications, see edge grinding overview, optical glass options, fused silica wafer applications.
Buyer questions, answered
What tolerances are achievable on Optical Glass parts?
Ground features hold +/-0.01 mm and lapped thickness reaches +/-0.003 mm. Index-certified blanks must be oriented and serialized through the shop to keep melt traceability.
What thickness range do you stock for Optical Glass?
Standard stock spans 0.30 – 50 mm, with blanks up to 300 mm diameter. Other formats are sourced per order.
How does Optical Glass behave under heat?
CTE is 7.1 x 10^-6 /K and continuous service reaches 400 C (Tg 557 C), which is what drives its use where certified refractive index and dispersion matters.
What accuracy does grinding hold?
Flatness to 5 um over 100 mm with minimum features of thickness to +/-0.005 mm. Subsurface damage of 5 – 15 um must be budgeted and removed by polishing on optical faces.
What equipment runs the grinding work?
Rotary surface grinders and double-disc machines with diamond wheels.
Specifications on this page were last reviewed by our engineering team in July 2026.