CVD Diamond (Optical) vs N-BK7
Glass · grade comparison
CVD Diamond (Optical) and N-BK7 are both glass grades. CVD Diamond (Optical) is the stronger of the two: tensile strength 400 MPa (58 ksi) against 50 MPa (7.25 ksi) for N-BK7, about 8.0 times as much. N-BK7 is lighter (2.51 g/cm³ vs 3.51 g/cm³ for CVD Diamond (Optical)) and CVD Diamond (Optical) is stiffer (1,140 GPa vs 82 GPa). On the shop floor, N-BK7 machines more easily (poor vs not recommended) and N-BK7 sits in a lower cost tier (standard, $$) than CVD Diamond (Optical) (high, $$$$).
CVD Diamond (Optical)Choose it when strength drives the design, or when the part sees heat.
N-BK7Choose it when weight is the constraint, or when the part is machined in volume.
CVD Diamond (Optical) vs N-BK7: propertiesHow to read these bars
- One bar per material. A full bar is the highest value among all glass grades in the FabDigit library; each bar is drawn as a share of that.
- The better value (by the usual engineering direction) is in bold. Rows with no direction — density, thermal conductivity — have no bold.
- Values are typical room-temperature figures for the condition named on each card.
- Confirm against the certified mill or resin datasheet before design release.
How to read these bars
- One bar per material. A full bar is the highest value among all glass grades in the FabDigit library; each bar is drawn as a share of that.
- The better value (by the usual engineering direction) is in bold. Rows with no direction — density, thermal conductivity — have no bold.
- Values are typical room-temperature figures for the condition named on each card.
- Confirm against the certified mill or resin datasheet before design release.
Mechanical
Strength, stiffness, ductility and hardness at room temperature.
Elastic (Young's) Modulus
Shear Modulus
Bulk Modulus
Poisson's Ratio
Tensile Strength (Ultimate)
Compressive Strength
Flexural Strength
Fracture Toughness (K_IC)
Hardness, Knoop
Hardness, Mohs
Elongation at Break
Shear Strength
Hardness, Vickers
Physical
Density and transition temperatures.
Density
Melting Point (Solidus)
Refractive Index
Light Transmission
Same in both: Porosity 0%
Thermal
How each material carries heat and how hot it can run.
Thermal Conductivity
Specific Heat Capacity
Thermal Expansion (CTE, 20–100 °C)
Max Service Temperature (continuous)
Min Service Temperature
Electrical
Conductivity and insulation.
Electrical Resistivity
Dielectric Constant (1 MHz)
Dissipation Factor (1 MHz)
Volume Resistivity
Dielectric Strength
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Corrosion Resistance
Manufacturability
FabDigit workshop ratings (0–100 scores) — how each material behaves on the machine.
Machinability
Polishability
Sustainability
Primary-production footprint per kilogram.
Typical Recycled Content
Embodied Energy (primary production)
Embodied Carbon (primary production)
Embodied Water
Common Calculations
Ratios derived from the values above.
Specific Strength (UTS / density)
Specific Stiffness (E / density)
Thermal Diffusivity
Thermal Shock Resistance Index
Strength versus weight
Yield strength against density for every glass grade in the FabDigit library; the compared grades are highlighted. Up and left is stronger for its weight.
Manufacturing and finishing
| Capability | CVD Diamond (Optical) | N-BK7 |
|---|---|---|
| Default condition | — | Annealed Glass |
| Relative cost | $$$$ High | $$ Standard |
| Min. machined wall | — | — |
| Best machined surface | — | — |
CVD Diamond (Optical) vs N-BK7 — frequently asked
Is CVD Diamond (Optical) stronger than N-BK7?
Yes. CVD Diamond (Optical) has a typical tensile strength of 400 MPa (58 ksi) against 50 MPa (7.25 ksi) for N-BK7 — about 8.0 times as much.
Which is cheaper, CVD Diamond (Optical) or N-BK7?
N-BK7 is the lower-cost material: it sits in the standard tier ($$) while CVD Diamond (Optical) is high ($$$$). Part price depends far more on geometry, tolerance and quantity than on raw stock — upload a CAD file for a live quote.
Which is easier to machine, CVD Diamond (Optical) or N-BK7?
N-BK7. Its machinability rates poor (18/100) against not recommended (1/100) for CVD Diamond (Optical).
Ready to make it?
Upload a CAD file and FabDigit prices the part in CVD Diamond (Optical) and N-BK7 side by side — material, machining time, tolerance and finish in one quote. Certified material data ships with the order on request.
Typical handbook values for the conditions named above, normalised for comparison. Hardness on non-Brinell scales is converted approximately for charting only. Request certified data with your order for design-critical properties.