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Instrument Glasses | Guidelines for Toughened Glass

Here at Instrument Glasses, Glass Manufacturers in Hertfordshire, we supply the best quality toughened laminated glass to suit your needs. With this in mind, our glass manufacturing company in Hertfordshire explains what toughened glass is and it’s guidelines.


What is toughened glass?

Toughened and/or tempered glass are types of safety glass with increased strength both physically and thermally. Processed in our state of the art toughening plant and heated up to 680 degrees depending on the thickness the toughening will create ‘balanced internal stresses’ which would mean that if broken the glass would crumble into small, less harmful pieces as opposed to dangerous large shards. Such properties mean that toughened glass is suitable for use in Shower Doors, Conservatories, Table Tops, Balustrades etc…


The toughening process begins with a piece of float or annealed glass placed on a roller table at the beginning of the toughening plant, this is where the BSI Kite Mark Stamp is put onto the glass. The rollers will take the glass first through the furnace which heats the glass to above its annealing point and then moved onto the quench where it is rapidly cooled. Once both processes are complete the glass will be toughened… But bear in mind that any cutting, drilling or processing must be completed prior to the toughening process otherwise the glass will shatter.


The finished product will be 5 times stronger than float glass of the same thickness and will therefore have a greater resistance to thermal shock and stresses.


Toughened glass guidelines

As a glass manufacturing company in Hertfordshire, Instrument Glasses ensures to adhere to the guidelines for toughened glass. The following guidelines for toughened glass are as follows.

  • Maximum hole diameter to be less than 50% of narrowest height/width of glass for holes over 75mm.

  • Minimum diameter 6mm but not less than thickness of glass

  • Distance between holes to be at least 4x thickness of glass

Distance to be 1.5 x thickness of glass up to 10mm glass and 2 x thickness of glass over 10 mm for holes at sides. Holes at corners distance to be 4 x thickness of glass from edge and at least 1.5 x thickness from other edge. Except where - glass thickness > 10mm to be 4 x thickness to both edges and where - angle of corner < 90 to be 4 x thickness to both edges

  • Polished internal cut-out must be minimum of 13mm radius

  • Non-polished cut-out must be minimum of 6mm radius

  • Radius of corners to be equal to the thickness of the glass

  • Interior width and height of cut-out not to be less than the thickness of the glass.

  • Distance between cut-out and edge of glass to be at least 50% of hole/cut-out width or height in the direction in question. Minimum of 75mm 4-6mm glass. Minimum of 100mm 8-19mm glass.

  • Height/width of cut-out to be no more than 30% of height/width of glass

Minimum 19mm radius at semi-circle of cut-out. Rectangular cut-outs to have a hole radius. Have radius corners or semicircular ends not less than the glass thickness.


Toughened Glass Manufacturers in Hertfordshire

If you would like more information about our toughened glass products, get in touch with our team today.



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