N-K5
N-K5 is a low-index, low-dispersion crown glass from the lead-free N-series optical catalogue, with a density of 2.59 g/cm³, CTE of about 8 µm/m·K and a glass transition near 546 °C.
Reference datasheet — N-K5 is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
What is N-K5?
N-K5 is a low-index, low-dispersion crown glass from the lead-free N-series optical catalogue, with a density of 2.59 g/cm³, CTE of about 8 µm/m·K and a glass transition near 546 °C. Engineers use it for the positive element of achromatic doublets and for general lens elements and windows, supplied fine-annealed, pressed or coarse-annealed (FA, PA, CA). Maximum service temperature is 400 °C, it is brittle and diamond-tooling only (machinability rating 35), and long hot-alkali cleaning leaches the surface. N-F2 is the usual flint partner. N-K5 has a density of 2.59 g/cm³ (0.0936 lb/in³), lighter than 59% of glass grades. N-K5 has a tensile strength of 40 MPa (5.8 ksi), weaker than 65% of glass grades. The elastic modulus is 71 GPa (10.3 Msi).
What is N-K5 used for?
- Achromatic doublets
- General lens elements
- Windows
Advantages
- Easy to machine — 35/100, better than 77% of glass grades
N-K5 properties
Typical room-temperature values; bars are the position among glass grades.
Physical4
N-K5 has a density of 2.59 g/cm³ (0.0936 lb/in³), lighter than 59% of glass grades.
Mechanical11
N-K5 has a tensile strength of 40 MPa (5.8 ksi), weaker than 65% of glass grades. The elastic modulus is 71 GPa (10.3 Msi).
Thermal5
N-K5 is rated for continuous service to 400°C (752 °F). It conducts heat at 1.1 W/m·K (0.624 BTU/hr·ft·°F), worse than 71% of glass grades. Thermal expansion is 8.2 µm/m·K (4.56 µin/in·°F).
Electrical5
N-K5 is an electrical insulator with a dielectric strength of 12 kV/mm (304.8 V/mil) and a resistivity of 1×10¹² Ω·m.
Chemical & Environmental2
Corrosion resistance is very good (70/100), worse than 58% of glass grades.
Sustainability4
Producing a kilogram of N-K5 takes about 42 MJ of energy and emits 2.6 kg of CO₂ — less than 67% of glass grades. Typical recycled content is 5%.
Manufacturability2
N-K5's machinability is fair (35/100, better than 77% of glass grades).
Common Calculations4
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the glass family
Yield strength against density for every glass grade FabDigit runs. N-K5 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with N-K5
Is N-K5 easy to machine?
Shaped only by diamond tooling — core drilling, curve generating, loose-abrasive lapping; feed lightly and flood-cool to avoid subsurface damage and edge chipping.
Can N-K5 be welded?
Not weldable; join by optical contacting, UV/epoxy cementing (achromat doublets) or elastomeric mounting, matching CTE ≈8 µm/m·K.
Can N-K5 be formed, bent or molded?
Hot pressed into near-net lens blanks around the softening range (T10^7.6 ≈ 659 °C); requires controlled step annealing below Tg ≈ 546 °C to hit catalogue index.
N-K5 chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| K2Oalkali of the classic K (potash crown) family | 6 – 14 | 10 |
| Na2Oapproximate | 2 – 10 | 6 |
| BaOindex/dispersion adjustment, approximate | 0 – 8 | 4 |
| ZnOapproximate | 0 – 8 | 4 |
| B2O3approximate | 0 – 6 | 3 |
| CaOapproximate | 0 – 5 | 2 |
| PbON-series: lead-free and arsenic-free by definition | 0 | 0 |
| SiO2network former; exact optical-glass batch is proprietary | ≥ 60 (balance) |
What surface finishes work on N-K5?
Polishes readily with cerium oxide to λ/10 and takes standard MgF2/multilayer AR coatings; keep off long hot-alkali cleaning cycles to prevent surface leaching.
How much does N-K5 cost?
N-K5 is a high-cost glass ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
N-K5 — frequently asked
What is N-K5 used for?
N-K5 is typically used for achromatic doublets, general lens elements and windows. In short: workhorse crown glass; low index, low dispersion; standard achromat positive element.
What is the tensile strength of N-K5?
N-K5 has a typical tensile strength of 40 MPa (5.8 ksi) — weaker than 65% of glass grades.
Is N-K5 easy to machine?
Not especially — machinability is rated fair (35/100, better than 77% of glass grades). Shaped only by diamond tooling — core drilling, curve generating, loose-abrasive lapping; feed lightly and flood-cool to avoid subsurface damage and edge chipping.
Can N-K5 be welded?
Not weldable; join by optical contacting, UV/epoxy cementing (achromat doublets) or elastomeric mounting, matching CTE ≈8 µm/m·K.
What surface finishes work on N-K5?
Polishes readily with cerium oxide to λ/10 and takes standard MgF2/multilayer AR coatings; keep off long hot-alkali cleaning cycles to prevent surface leaching.
Can N-K5 be formed, bent or molded?
Hot pressed into near-net lens blanks around the softening range (T10^7.6 ≈ 659 °C); requires controlled step annealing below Tg ≈ 546 °C to hit catalogue index.
What is the maximum service temperature of N-K5?
N-K5 is rated for continuous use to about 400°C (752 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does N-K5 cost?
N-K5 is a high-cost glass ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Sources
- Optical Glass Data Sheet N-K5 — SCHOTT AG (2023)
- TIE-19 Temperature Coefficient of the Refractive Index / TIE-33 Design Strength of Optical Glass — SCHOTT AG (2020)
- ASM Engineered Materials Handbook Vol. 4 — Ceramics and Glasses — ASM International (1991)
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.