Polishing Fused Silica: Fused Silica (CTE 0.55 x 10^-6 /K, 185 nm – 2.5 um); Polishing to flatness to lambda/4 per 25 mm. Single-piece prototypes to production volumes, quoted from your drawing.
The combination of Fused Silica and Polishing comes up constantly in RFQs for a reason – the material offers deep-uv transmission, and Polishing is the right way to get accurate geometry into it. Expect flatness to lambda/4 per 25 mm and scratch-dig 40/20 to 20/10.
The numbers
| Material | Fused Silica (JGS1 (UV), JGS2 (standard), JGS3 (IR)) |
|---|---|
| Thermal expansion (CTE) | 0.55 x 10^-6 /K |
| Service temperature | 1,100 C continuous |
| Transmission range | 185 nm – 2.5 um |
| Density | 2.20 g/cm3 |
| Knoop hardness | 500 kg/mm2 |
| Refractive index | 1.458 @ 587 nm |
| Stock thickness | 0.10 – 50 mm |
| Maximum blank size | 450 x 450 mm |
| Process | Polishing |
| Working tolerance | flatness to lambda/4 per 25 mm |
| Minimum feature | Ra below 1 nm |
| Surface finish | scratch-dig 40/20 to 20/10 |
| Thickness window | 0.2 – 50 mm |
| Edge condition | polished bevels available |
| RFQ inputs | PDF/DXF/STEP drawing, quantity brackets, surface and edge spec |
Specification advice
The shop-floor rules that matter here:
- Material note: its hardness and brittleness demand diamond tooling and controlled feeds.
- Process boundary: steep aspect parts and deep pockets polish unevenly; those faces are specified as fine-ground.
- 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.
Capabilities and limits
The core strength of Polishing is optical-grade faces with certified scratch-dig and interferometer-verified flatness. The honest limit: steep aspect parts and deep pockets polish unevenly; those faces are specified as fine-ground. Both belong on the drawing before quoting, not after.
One material, many routes: on Fused Silica we also quote sandblasting, edge grinding, ultrasonic machining, etching, and multi-step drawings are the norm rather than the exception.
Application context
polishing fused silica shows up across optical sensors (sensor windows, filter caps, lens covers); semiconductor equipment (view ports, wafer carriers, plasma rings, chamber windows); machine vision (camera windows, ring-light diffusers, calibration plates). Background reading on the underlying material science: RP Photonics: fused silica.
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.
Useful companion pages: material selection guide, fused silica material guide, precision glass drilling.
Buyer questions, answered
What tolerances are achievable on Fused Silica parts?
Ground features hold +/-0.01 mm and lapped thickness reaches +/-0.003 mm. Its hardness and brittleness demand diamond tooling and controlled feeds.
What thickness range do you stock for Fused Silica?
Standard stock spans 0.10 – 50 mm, with blanks up to 450 x 450 mm. Other formats are sourced per order.
How does Fused Silica behave under heat?
CTE is 0.55 x 10^-6 /K and continuous service reaches 1,100 C continuous, which is what drives its use where near-zero thermal expansion matters.
What accuracy does polishing hold?
Flatness to lambda/4 per 25 mm with minimum features of Ra below 1 nm. Steep aspect parts and deep pockets polish unevenly; those faces are specified as fine-ground.
What equipment runs the polishing work?
Pitch and polyurethane pad polishers with cerium oxide slurry.
Specifications on this page were last reviewed by our engineering team in July 2026.