Polishing Borosilicate Glass: Borosilicate Glass (CTE 3.3 x 10^-6 /K, 360 nm – 2.0 um); Polishing to flatness to lambda/4 per 25 mm. Single-piece prototypes to production volumes, quoted from your drawing.
Ask any process engineer what makes borosilicate glass difficult and the answer is specific: sheet stock carries more thickness variation than float wafer stock, so lapping is often the first step. Our polishing line is tooled around exactly that – pitch and polyurethane pad polishers with cerium oxide slurry – holding flatness to lambda/4 per 25 mm on parts from 0.2 – 50 mm thick.
Specification envelope
| Material | Borosilicate Glass (3.3 expansion group per ISO 3585) |
|---|---|
| Thermal expansion (CTE) | 3.3 x 10^-6 /K |
| Service temperature | 450 C continuous |
| Transmission range | 360 nm – 2.0 um |
| Density | 2.23 g/cm3 |
| Knoop hardness | 480 kg/mm2 |
| Refractive index | 1.473 @ 587 nm |
| Stock thickness | 0.50 – 30 mm |
| Maximum blank size | 600 x 400 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 |
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 Borosilicate Glass we also quote sandblasting, laser cutting, drilling, double-side polishing, and multi-step drawings are the norm rather than the exception.
Design guidance
Before sending the RFQ, check these against your drawing:
- Material note: sheet stock carries more thickness variation than float wafer stock, so lapping is often the first step.
- 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.
The full rules live in our tolerance design guide and holes and edges design guide.
Application context
Orders for polishing borosilicate glass cluster in medical diagnostics (flow cells, slides, microplate bottoms, cuvette windows); scientific instruments (reference flats, cells, prism mounts, stage inserts); laboratory instruments (cuvettes, sight glasses, stir-cell windows). Background reading on the underlying material science: ISO 3585 borosilicate glass 3.3.
Dimensions still moving? Configure this part live in the 3D + 2D builder below, or open the full custom glass machining 3D + 2D builder to start from a blank canvas.
Useful companion pages: glass sandblasting, optical polishing capability, custom microfluidic chip.
Common questions
What equipment runs the polishing work?
Pitch and polyurethane pad polishers with cerium oxide slurry.
Is there a minimum order for polishing borosilicate 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.