WHY GMT GRANITE PRODUCTS?
GMT is a manufacturer and supplier of granite surface plates of grade 00, grade 0, grade 1. grade 2 and grade 3. GMT’s granite and Cast Iron Products are made at The Metrology Division in Hosur, Tamil Nadu, India, close to rich sources and large deposits of high-quality granite, well suited for Metrology applications.
Indian black granite is best suited for metrology application as this granite has a very fine-grained structure. Some of the properties that help select a rock for metrology application are Co-efficient of thermal expansion, density, water absorption & porosity, flexural and compressive strength.
SPECIFICATIONS
FLATNESS TOLERANCE IN µm FOR ACCURACY GRADE
AS PER IS 7327-2003 / * AS PER DIN 876:84
| SIZE (in mm) | GRADE “00” * | GR “0” | GRADE “1” | GRADE “2” | GR “3” | WEIGHT (kg) |
| 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 |
APPLICATION
Surface plates are used as reference planes for dimensional inspection and calibration of mechanical artefacts. This plate acts as a datum surface, providing the X and Y coordinates for dimension measurements. So, the flatness of the plate is critical. For that reason, this flatness measurement commonly carries a tolerance and may include a grade designation. Besides, GMT Metrology Granite Surface Plates meet the DIN and IS Standards specified in the table above. Also, GMT Granite Surface Plates are manufactured to precision standards using the highest quality granite.
ACCURACY
First of all, rigorous quality control inspection is carried out at all stages. Finally, inspection is carried out with a High Precision Computerised Electronic Level calibrated by an NABL accredited lab at regular intervals.
ACCURACY UNDER LOAD
Granite Surface Plates can support a total normal load of 25 kgs. per 0.1 sq.m.
CERTIFICATE OF ACCURACY
A certificate of accuracy is supplied with each plate as per the standards specified by the customer, such as IS, DIN, BS, and JIS.
TECHNICAL DATA
Granite Surface Plates are manufactured in five grades. The typical application of these five grades of plates is as under :
- GRADE 00 as per DIN : 876: 84 is of laboratory grade. It is specified for precision measurement in gauge rooms and metrology laboratories for calibration masters.
- GRADE 0 is of inspection grade. It is specified for general work in quality control.
- GRADE 1 is of tool room grade. It is specified for production checking work through the shop.
- GRADE 2 & 3 are intended for use in shops for general inspection.
MATERIAL
Granite Surface Plates are made from select granite with uniform distribution of light and dark constituents. In such granite, the minerals are evenly distributed, resulting in a homogenous appearance. The following are the representative properties of our granites :
Coefficient of Thermal Expansion
Texture : Fine
Specific Gravity : 3.08 g/cm3
Hardness : Scleroscope over 90
Modulus of Elasticity : 9.0 to 12.0 x 105kg/cm2
Moisture of absorption : Nil
FLATNESS TOLERANCE
The flatness deviation of a local area of 250 mm x 250 mm of the working surface shall not exceed
- 3.0 µm for plates of Grade 00
- 3.5 µm for plates of Grade 0
- 7.0 µm for plates of Grade 1
- 15.0 µm for plates of Grade 2
- 30.0 µm for plates of Grade 3
GRANITE SURFACE PLATE STANDS
These are fabricated of heavy angle iron and reinforced to ensure rigidity. The stands are designed to withstand the weight of the granite surface plates and are supplied with three levelling screws for levelling the granite surface plates.
OPTIONAL ACCESSORIES
The plate is supplied with a suitable rexine cover to protect both the plate’s working surface and side faces at extra cost.
Finally, please visit us at https://gmtmachinetools.blogspot.in – a new blog dedicated to all GMT customers…interact with our technical experts.
