24 Questions
What is a surface plate used for?
As a benchmark for all measurements
A surface plate can be easily bent or warped by an external force.
False
What is the purpose of a calibration certificate for a surface plate?
To emphasize flatness complying to the standards
A surface plate must be made of a material that is resistant to ______________ and corrosion.
wear
What is flatness in the context of a surface plate?
The 3D version of straightness
Match the following applications with the type of surface plate:
Precision gauging = Measuring dimensions Inspection = Checking flatness Tooling setup = Setting up tools
A surface plate can be used to confirm the flatness of other materials and measuring tools.
True
What are the requirements for the material used to manufacture a surface plate?
The material must have a high degree of rigidity, resistance to wear and corrosion, and be free from warping
What is a common method of using a height gage to evaluate flatness on a surface plate?
Placing the part directly on the table
Surface plates should be calibrated only once a year.
False
What is the primary use of a surface plate?
To test the flatness of other surfaces or to provide a truly flat datum surface in marking off work for machining.
The flatness accuracy of the surface plate must be checked on a __________ basis to make sure the surface is in an ideal condition.
regular
Match the following precautions with their corresponding descriptions:
Check flatness accuracy regularly = Clean the top surface before use To make sure the surface is in an ideal condition = To avoid dust and other polluted particles
What is the greatest source of wear and tear on a surface plate?
Airborne abrasive dust
Surface plates are used to test the flatness of other surfaces only.
False
What is the recommended frequency for calibrating surface plates?
Every six months.
What is the overall flatness of a surface plate?
The flatness of the entire working surface
Glass Surface Plates are still widely used in industry today.
False
What is the standard size for local flatness measurement?
250 mm × 250 mm
The accuracy of overall flatness depends on the __________________ and grade of the surface plate.
size
What is the main disadvantage of Cast Iron Surface Plates?
They are prone to rust
What is the result of adding the highest and lowest measured points on a surface plate?
Flatness
Match the following surface plate types with their corresponding standards:
Granite Surface Plate = ISO 8512-2 Cast Iron Surface Plate = ISO 8512-1 Glass Surface Plate = Indian standard (IS 14900)
Cast Iron Surface Plates are resistant to thermal expansion.
False
Study Notes
What is a Surface Plate?
- A surface plate is a very flat surface, also known as the true plane, with high accuracy of flatness, squareness, and straightness.
- It serves as a benchmark for all measurements.
Properties of a Surface Plate
- Must have a high degree of rigidity to withstand heavy loads and resist bending.
- Must have resistance to wear and corrosion.
- Must be free from warping and twisting.
Material Properties of a Surface Plate
- Flatness refers to the difference between the highest and lowest points on a surface, within a tolerance zone.
- Flatness is measured in 3D, whereas straightness is measured in 2D.
Applications of Surface Plates
- Used to test the flatness of other surfaces or provide a truly flat datum surface for machining.
- Used with a height gage to evaluate flatness.
Precautions while using Surface Plates
- Regularly check the flatness accuracy of the surface plate.
- Clean the top surface before use to avoid dust and polluted particles.
- Cover the top surface when not in use to prevent damage.
- Use the plate uniformly to avoid uneven wear.
- Coat the top surface with corrosion-resistant elements like oil or grease after use.
Surface Plates Checks and Calibration
- Surface plates check and zero out other pieces of equipment.
- Calibrate surface plates regularly, ideally every six months, to ensure accuracy.
Types of Surface Plates
- According to material used, there are two major types: Granite Surface Plate (ISO 8512-2) and Cast Iron Surface Plate (ISO 8512-1).
- Glass Surface Plate is also available, but not preferable due to its fragility.
A surface plate is a highly accurate flat surface used as a benchmark for measuring flatness, squareness, and straightness of other materials and tools.
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