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Limitations and Precautions in Secondary Processing of Tempered Glass
Tempered glass is widely valued for its strength and safety, but once the tempering process is complete, secondary processing becomes extremely limited. Understanding these restrictions and proper handling methods is essential to prevent breakage and ensure safe application.
Tempering strengthens glass by heating it to around 620 °C and then rapidly cooling the surface. This creates internal compressive stress that increases its mechanical strength several times compared to ordinary glass. However, this same stress is what makes post-tempering machining nearly impossible. Any cutting, drilling, or grinding applied after tempering will disrupt the stress balance and cause the entire piece to shatter instantly.
Therefore, all dimensional modifications—such as cutting, edge grinding, or hole drilling—must be completed before the glass is tempered. During design, precise drawings should specify hole sizes, positions, and edge shapes in advance. Even small adjustments afterward are not feasible.
When secondary processing is unavoidable, some manufacturers may recommend heat-soak testing or controlled annealing to partially relieve internal stress, but this often compromises strength and transparency. Instead of reworking tempered glass, replacing it with a new, properly processed sheet is usually the safer and more economical choice.
Other precautions include handling tempered glass carefully during installation. Avoid strong edge impacts or uneven surface pressure, as these can trigger spontaneous breakage. For applications requiring complex shapes or multiple openings, laminated glass or heat-strengthened glass may provide greater flexibility while maintaining safety performance.
In short, while tempered glass offers outstanding durability, its unique internal stress structure limits post-processing options. Proper design planning, precision cutting, and complete finishing before tempering are the keys to achieving both strength and design accuracy without risk.
