Lapping Fused Silica – Fused Silica (CTE 0.55 x 10^-6 /K, 185 nm – 2.5 um); Lapping to flatness 1 – 3 um. No minimum order; DFM review included with every RFQ.
Ask any process engineer what makes fused silica difficult and the answer is specific: its hardness and brittleness demand diamond tooling and controlled feeds. Our lapping line is tooled around exactly that – cast-iron lap plates with boron carbide and alumina slurries – holding flatness 1 – 3 um on parts from 0.2 – 40 mm thick.
Specification envelope
| 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 | 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 |
Process window
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, Fused Silica routinely runs through dicing, double-side polishing, drilling, grinding in our shop – most real parts combine two or three of these steps.
Getting the drawing right
Before sending the RFQ, check these against your drawing:
- Material note: its hardness and brittleness demand diamond tooling and controlled feeds.
- 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.
Where these parts end up
The recurring buyers of lapping fused silica: aerospace optics (sensor windows, star-tracker flats, radiation-tolerant ports); scientific instruments (reference flats, cells, prism mounts, stage inserts); laser systems (windows, beam splitters, debris shields). Background reading on the underlying material science: RP Photonics: fused silica.
The fastest route to a quote is geometry: use the 3D configurator below, or the site-wide custom glass machining 3D builder for fully custom parts.
Engineers scoping this work usually also review fused silica material guide, material selection guide, AR coated glass materials.
Common questions
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 lapping hold?
Flatness 1 – 3 um with minimum features of thickness +/-0.003 mm. Lapped faces are translucent-matte; optical clarity requires a subsequent polish.
Specifications on this page were last reviewed by our engineering team in July 2026.