Coring Optical Glass – Optical Glass (CTE 7.1 x 10^-6 /K, 350 nm – 2.0 um); Coring to diameter +/-0.05 mm. No minimum order; DFM review included with every RFQ.
The combination of Optical Glass and Coring comes up constantly in RFQs for a reason – the material offers striae and stress-birefringence control, and Coring is the right way to get accurate geometry into it. Expect diameter +/-0.05 mm and ground bore, honed option.
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 | Coring |
| Working tolerance | diameter +/-0.05 mm |
| Minimum feature | 2 mm core diameter |
| Surface finish | ground bore, honed option |
| Thickness window | 1 – 60 mm |
| Edge condition | entry/exit chamfer standard |
| RFQ inputs | PDF/DXF/STEP drawing, quantity brackets, surface and edge spec |
Specification advice
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: wall thickness between adjacent cores should exceed 2 mm to avoid bridge cracking.
- 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
Coring earns its place through large-diameter discs, rings and through-bores from plate stock up to 60 mm thick. Its boundary condition – wall thickness between adjacent cores should exceed 2 mm to avoid bridge cracking – is the first thing our DFM review checks.
Beyond this page, Optical Glass routinely runs through ultrasonic machining, etching, double-side polishing in our shop – most real parts combine two or three of these steps.
Who orders this
The recurring buyers of coring optical glass: scientific instruments (reference flats, cells, prism mounts, stage inserts); laser systems (windows, beam splitters, debris shields); machine vision (camera windows, ring-light diffusers, calibration plates). 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.
Related reading on this site: optical polishing capability, optical glass options, precision glass grinding.
Frequently asked questions
What equipment runs the coring work?
Diamond core drills with rotary fixtures.
Is there a minimum order for coring 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.
Specifications on this page were last reviewed by our engineering team in September 2026.