KRS-5 vs N-BK7
Glass · grade comparison
KRS-5 and N-BK7 are both glass grades. N-BK7 is the stronger of the two: tensile strength 50 MPa (7.25 ksi) against 26 MPa (3.77 ksi) for KRS-5, about 92% more. In exchange, KRS-5 is the more ductile: elongation 2% versus 0% for N-BK7, and N-BK7 is harder (610 HV vs 40 HV). N-BK7 is lighter (2.51 g/cm³ vs 7.37 g/cm³ for KRS-5) and N-BK7 is stiffer (82 GPa vs 15.9 GPa). On the shop floor, KRS-5 machines more easily (good vs poor) and N-BK7 sits in a lower cost tier (standard, $$) than KRS-5 (high, $$$$).
KRS-5Choose it when the part is bent, formed or impact-loaded, or when the part is machined in volume.
N-BK7Choose it when strength drives the design, or when weight is the constraint.
KRS-5 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)
Elongation at Break
Compressive Strength
Flexural Strength
Shear Strength
Fracture Toughness (K_IC)
Hardness, Vickers
Hardness, Knoop
Hardness, Mohs
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)
Dielectric Strength
Volume Resistivity
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.
Embodied Energy (primary production)
Embodied Carbon (primary production)
Embodied Water
Typical Recycled Content
Common Calculations
Ratios derived from the values above.
Specific Strength (UTS / density)
Specific Stiffness (E / density)
Same in both: Thermal Diffusivity 0.5 mm²/s · Thermal Shock Resistance Index 0
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 | KRS-5 | N-BK7 |
|---|---|---|
| Default condition | — | Annealed Glass |
| Relative cost | $$$$ High | $$ Standard |
| Min. machined wall | — | — |
| Best machined surface | — | — |
KRS-5 vs N-BK7 — frequently asked
Is N-BK7 stronger than KRS-5?
Yes. N-BK7 has a typical tensile strength of 50 MPa (7.25 ksi) against 26 MPa (3.77 ksi) for KRS-5 — about 92% more.
Which is cheaper, KRS-5 or N-BK7?
N-BK7 is the lower-cost material: it sits in the standard tier ($$) while KRS-5 is high ($$$$). 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, KRS-5 or N-BK7?
KRS-5. Its machinability rates good (55/100) against poor (18/100) for N-BK7.
Ready to make it?
Upload a CAD file and FabDigit prices the part in KRS-5 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.