Optical Glass · Borosilicate
N-BK7
N-BK7 is an optical glass glass — premium optical glass. Typical values: 60 MPa yield, 2.51 g/cm³, rated to 500 °C. Available for CNC machining, Sheet metal at FabDigit.
Properties
Typical room-temperature values in the Annealed Glass condition. Metric first, imperial in gray. The bars show where N-BK7 sits against the other 8 glass grades in the catalog.
Datasheet
| Yield strength | 60 MPa9 ksi |
|---|---|
| Tensile strength | 70 MPa10 ksi |
| Hardness | 610 HV≈ 580 HB |
| Density | 2.51 g/cm³0.091 lb/in³ |
| Specific strength (yield ÷ density) | 24 |
| Min service temp | -200 °C-328 °F |
| Max service temp | 500 °C932 °F |
| Electrical conductivity | < 0.001 % IACSinsulator |
| Machinability | Poor20 / 100 |
| Weldability | Not recommended5 / 100 |
| Formability | Not recommended5 / 100 |
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Against other glass grades
Strength versus weight in the glass family
Yield strength against density for every glass grade FabDigit runs. N-BK7 is highlighted; hover a dot for its name, or open the interactive family chart.
Manufacturability
The process limits FabDigit's quote engine applies to N-BK7. Design inside these and the part quotes instantly; outside them it routes to an engineer.
CNC machining
| Machinability | Poor20 / 100 |
|---|---|
| Cutting speed (rough / finish) | — / — |
| Minimum wall | — |
| Minimum internal radius | — |
| Drill depth limit | — |
| Best surface (machined / polished) | Ra — / — |
| Hardenable after machining | — |
Sheet metal
| Formability | Not Recommend5 / 100 |
|---|---|
| Weldability | Not Recommend5 / 100 |
Conditions and tempers
How N-BK7 is supplied and what each state is for. The default is what FabDigit quotes unless your drawing says otherwise.
| Condition | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
Annealed GlassDefault Heat Treat State | Standard glass — can still be cut and drilled to size | — | — | — | — |
Heat treatment and post-processing
Operations FabDigit's suppliers routinely run on N-BK7, ranked by how often they make sense for this grade.
Post-processing
| Manual Deburr | Deburrstandard |
|---|---|
| Edge Break (0.5mm) | Deburr |
| CMM Inspection | Inspection |
| FAI Report | Inspection |
| Individual Bag | Packaging |
Surface finishes for N-BK7
Coatings and treatments compatible with glass on the processes N-BK7 runs on. Pick them in the quote configurator or call them out on the drawing.
Marking / Decoration
- Chemical Etching
- Dot Peen Marking
- Electro-chemical Etching
- Embossing / Debossing
- Ink Stamping
- Laser Marking
- Mechanical Engraving
- Vibro Engraving / Scribing
Equivalent designations
Standards and trade names that resolve to N-BK7 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- Trade names
- Optical Borosilicate
- Other
- BK7Schott N-BK7
Stock forms
Raw-material forms FabDigit sources N-BK7 in.
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.