BUMAX screws for ELT11 June 2020

Stainless steel fasteners manufacturer BUMAX has been chosen to supply thousands of fasteners for the ELT (Extremely Large Telescope), which is presently under construction.

The firm has received an order for 11,000+ fasteners (model BUMAX 109) for the construction of the European Southern Observatory Extremely Large Telescope (ESO ELT). It is said that the ELT will be the ‘world’s largest telescope’ when it goes operational in the dry Atacama desert in northern Chile in 2024.

The ELT (pictured) is a reflector telescope that will collect universal light using a curved mirror that is 39 metres across. Such a giant mirror is much too large to be made from a single piece of glass, so it will consist of 798 individual hexagonal segments, each measuring 1.4 metres across and driven by electrical motors for fine tuning.

BUMAX fasteners are being used to fix the nearly 800 telescope mirrors to all the segment supports. Twelve pieces of 10mm long BUMAX 109 M6 bolts per segment are used for more than 900 segments in total (the 798 support segments plus an additional 133 segments for a continuous swapping process to allow the mirrors to be cleaned and coated while the ELT stays operational).

Patrik Lundström Törnquist, MD at BUMAX, says: “This order is yet another testament to BUMAX being able to provide the very best fasteners for the most demanding applications."

The ELT is presently under construction by the Dutch company VDL ETG Projects in the Netherlands. Michael Evers, project manager at VDL ETG, says: “Standard stainless steel bolts lack the strength required for the ELT. We required a 10.9 strength bolt, and with the corrosion resistance of stainless steel. BUMAX offered us the perfect solution.

“The high strength BUMAX 109 fasteners prevent damage to the mirror segments, which is very costly. Their corrosion resistance is also essential as the fasteners are sometimes open to the elements and will reduce future maintenance requirements.”

Adam Offord

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