Holding together the world’s largest telescope 04 September 2020

BUMAX has been chosen to supply thousands of high strength and corrosion resistant fasteners for the ELT, Extremely Large Telescope, currently under construction in the Netherlands.

The €1 billion ELT will be the world’s largest telescope when it becomes operational in northern Chile in 2024. It is a reflector telescope, collecting universal light using a massive curved mirror that is 39m across – 3 times the area of the next largest telescope.

The giant mirror will consist of 798 individual hexagonal segments each measuring 1.4m across and will be driven by electrical motors for fine-tuning. An additional 133 segments have also been made for a continuous swapping process, which will allow the ELT to stay operational whilst the mirrors are coated and cleaned. The segments will work together as a single mirror to collect 100 million times more light than the human eye.

BUMAX® fasteners are being used to fix the individual telescope mirrors to the segment supports. Twelve 10mm BUMAX 109 M6 bolts are used on each of the 931 segments.

Customised bolts require special tools
The ELT is presently under construction by Dutch company VDL ETG Projects. Michael Evers, project manager at VDL ETG, said: “Standard stainless steel bolts lack the strength required. 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.”

The bolts are a customised product that have been coated with a special surface treatment and require special tools to manufacture.

“This order is yet another testament to BUMAX being able to provide the very best fasteners for the most demanding applications. We have also been trusted with supplying fasteners for the CERN accelerator in Switzerland, as well as satellites, and submarines,” explained Patrik Lundström Törnquist, managing director at BUMAX.

Deputy Editor

Claire Aldridge Deputy Editor t: +44 (0) 1727 814 450


Having joined the magazine in 2012, Claire developed her knowledge of the industry through the numerous company visits, exhibitions and conferences she attended both in the UK and abroad.

Claire prides herself on keeping readers well informed and up to date with the latest industry news.