GMT PRECISION GRANITE SURFACE PLATES

Why GMT Granite Products?
GMT's metrology division is located at Hosur, Tamil Nadu. This region is home to large deposits of world famous Indian black diabase granite which is is best suited for metrology application as it has  a very fine-grained structure. The properties, which help in selecting a rock for metrology application are density, water absorption & porosity, flexural and compressive strength.

Advantages of Indian Black Granite:

• Low coefficient of expansion and thermal stability
• Water absorption and porosity is low and hence long term dimensional stability is good
• It is fine-grained and the density & hardness is suited for dimensional metrology
• Flexural strength, Compressive strength, Modules of rupture and Tensile stress
• Totally corrosion free, granite does not rust nor corrode or react chemically with other substances
• Non Magnetic and non-conductive
• Non-reflective matt finish
• High flatness accuracy
• Ideal for guideways for measuring instuments and air bearing surfaces
• High bending strength
• Insensitive to mechanical overloading
• All calibration equipment is to national and international laboratories standards
• Hand lapped for maximum accuracy

SPECIFICATIONS

FLATNESS TOLERANCE IN µm FOR ACCURACY GRADE 

SIZE OF PLATE             AS PER DIN 876:84                      AS PER IS 7327-2003                                        WEIGHT

   (in mm)            |  GRADE "00" | GRADE "0" | GRADE "1" | GRADE "2" | GRADE "3" | (Kgs) (Approx.)

250 x 250        |            3          |       3.5        |         7          |      15          |      30          |      10
300 x 300        |            3          |       3.5        |         7          |      15          |      30          |      22
400 x 250        |            3          |       4.0        |         8          |      16          |      32          |      20
400 x 400        |            3          |       4.5        |         9          |      17          |      34          |      40
500 x 300        |            3          |       4.5        |         9          |      17          |      34          |      35
630x 400         |            4          |       5.0        |        10         |      20          |      39          |      65
630 x 630        |            4          |       5.0        |        10         |      21          |      42          |     100
800 x 500        |            4          |       5.0        |        10         |      21          |      42          |     120
1000 x 630      |            4          |       6.0        |        12         |      24          |      49          |     320
1000 x 1000    |            4          |       7.0        |        14         |      28          |      56          |     500
1200 x 800      |            4          |       7.0        |        14         |      28          |      56          |     475
1600 x 1000    |            5          |       8.0        |        16         |      33          |      66          |    1100
2000 x 1000    |            6          |       9.5        |        19         |      38          |      75          |    1650

TO MEET SPECIAL REQUIREMENTS WE OFFER :

1. Sizes larger than 2000 X 1000 mm. The thickness of the plate increases with size.
2. Granite Surface Plates with inserts with drilled and tapped inserts
3. Granite Straight Edges
4. Granite Master Squares
5. Granite Cubes
6. Master Cylinder made of hardened and ground steel