Grinding Borofloat 33 – Borofloat 33 (CTE 3.25 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.
Ask any process engineer what makes borofloat 33 difficult and the answer is specific: float tin side must be tracked when parts see coating or bonding steps. Our grinding line is tooled around exactly that – rotary surface grinders and double-disc machines with diamond wheels – holding flatness to 5 um over 100 mm on parts from 0.3 – 60 mm thick.
Specification envelope
| Material | Borofloat 33 (SCHOTT float production, wafer grade) |
|---|---|
| Thermal expansion (CTE) | 3.25 x 10^-6 /K |
| Service temperature | 450 C continuous |
| Transmission range | 350 nm – 2.0 um |
| Density | 2.23 g/cm3 |
| Knoop hardness | 480 kg/mm2 |
| Refractive index | 1.471 @ 587 nm |
| Stock thickness | 0.70 – 25.4 mm |
| Maximum blank size | 500 x 500 mm |
| 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 |
Manufacturing capability
The core strength of Grinding is bringing thickness, flatness and parallelism into calibrated tolerance before polish. The honest limit: subsurface damage of 5 – 15 um must be budgeted and removed by polishing on optical faces. Both belong on the drawing before quoting, not after.
One material, many routes: on Borofloat 33 we also quote laser cutting, cnc machining, sandblasting, lapping, and multi-step drawings are the norm rather than the exception.
Design guidance
The shop-floor rules that matter here:
- Material note: float tin side must be tracked when parts see coating or bonding steps.
- 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.
The full rules live in our tolerance design guide and holes and edges design guide.
Who orders this
The recurring buyers of grinding borofloat 33: optical sensors (sensor windows, filter caps, lens covers); machine vision (camera windows, ring-light diffusers, calibration plates); led packaging (groove covers, phosphor carriers, package windows). Background reading on the underlying material science: SCHOTT BOROFLOAT product page.
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 Borofloat 33 selection guide, edge grinding overview, fused silica wafers 2-12 inch.
Buyer questions, answered
What tolerances are achievable on Borofloat 33 parts?
Ground features hold +/-0.01 mm and lapped thickness reaches +/-0.003 mm. Float tin side must be tracked when parts see coating or bonding steps.
What thickness range do you stock for Borofloat 33?
Standard stock spans 0.70 – 25.4 mm, with blanks up to 500 x 500 mm. Other formats are sourced per order.
How does Borofloat 33 behave under heat?
CTE is 3.25 x 10^-6 /K and continuous service reaches 450 C continuous, which is what drives its use where float-glass flatness off the line 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.
Specifications on this page were last reviewed by our engineering team in July 2026.