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Story behind GMT’s Extra Large Size Granite Surface Plate


Guindy Machine Tools Limited (GMT) recently manufactured and supplied an extra-large sized granite surface plate measuring a whopping 12m in length.

  • Granite Table for marine crankshaft inspection
  • Size: 12000mm x 1500mm x 500mm
  • Flatness: 50 micrometer
  • With T-Slot – Straightness 10 micrometer per metre

The Story behind this milestone achievement…

Apart from complete range of standard granite and cast-iron metrology dimensional inspection equipment, GMT’s Metrology Division offers custom built metrology products like large size granite plates and granite base structures for Special Purpose Machines.

It is an acknowledged fact that granite from the Deccan plateau in South India, where GMT’s metrology division is located, is the most suited for metrology. On receiving the order, experts from GMT visited several quarries in this region to select a single block of granite measuring a minimum of 15m x 2m x 1m. Choosing the stone is a crucial first step in any precision granite product – As granite is a natural material and its properties can vary from vein to vein in the quarry, GMT initially identifies the correct vein in the quarry to source the stone, for such special pieces.

Finally, they located a single piece of granite suitable for this application. It was then transported to the factory. Our team of experts cut the granite block to size. It was then hand lapped to perfection. GMT has supplied thousands of surface plates to the Indian manufacturing industry. This is the largest single piece surface plate by GMT in the company’s 60 years of existence.

The T-Slots were another story…

The plate was too long, large and heavy to accommodate within the factory. Hence, the finishing was in the open air. Once rough finishing was completed, a temperature-controlled room was built around it to finish and inspect it.

Inspecting the Surface Plate in a specially built temperature-controlled room.
Finished Surface Plate ready for despatch.

Once finished, packing and transporting it to the customer was unlike any other item. Transporting the plate without damage over 550 miles (883 km) was another challenge. Besides, parts of the journey were over mountainous sections. It was coordinated and achieved with the same precision for which GMT is known for its products. The truck reached the customer’s site in record time.  Finally, the mounting of the plate on vibration dampers and commissioning at the customer’s site was successful.

4 Cranes working in tandem to load the plate on to the truck
B. Venugopal, Managing Director

“This was a huge achievement for us. Our experience in the production of metrology equipment over five decades has helped us in this project” explained B.Venugopal, Managing Director of GMT.  “The fact that we were able to achieve plate flatness of 50micron and T-Slot straightness of 10 microns per meter, speaks volumes for our expertise. We are confident to take on such projects with all the QC challenges involved in producing metrology products. This will help in inspection of large components, to meet the needs of especially the marine, automobile and other industries requiring very special precision dimensional measurements.”


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