Marking Media and Their Applications
Marking media are substances used in workshop practice to make visible layout lines on metal surfaces before performing operations such as cutting, drilling, filing, or machining. Proper marking helps the technician perform accurate work and reduces errors during fabrication. Various marking media are used depending on the type of material and the purpose of marking.
Marking Blue
Marking blue is a special type of dye applied to metal surfaces to make scribed lines clearly visible. It is usually available in liquid or paste form and is applied in a thin layer over the workpiece surface. When the surface is coated with marking blue, layout lines drawn with a scriber appear bright and clear against the blue background.
Applications of Marking Blue:
- Used for precision layout work on metal surfaces.
- Helps in marking accurate lines during fitting operations.
- Provides clear contrast for scribed lines.
- Commonly used in machine shops and tool rooms.
Prussian Blue
Prussian blue is a dark blue pigment used mainly for checking the contact surfaces of machine parts. It is applied as a very thin layer on one surface. When another surface is placed against it, the high spots become visible due to the transfer of the blue pigment.
Applications of Prussian Blue:
- Checking surface contact between machine components.
- Identifying high spots on bearing surfaces.
- Used during scraping and fitting operations.
Red Lead
Red lead is a red-colored marking compound used for marking rough surfaces where other marking media may not be clearly visible. It is often mixed with oil to form a paste before application.
Applications of Red Lead:
- Marking rough cast surfaces.
- Marking heavy metal components.
- Used in fabrication and fitting work.
Chalk
Chalk is one of the simplest marking media used in workshops. It is usually applied on rough or dark surfaces to make marking lines visible. Chalk is inexpensive and easy to use but not suitable for precision marking.
Applications of Chalk:
- Temporary marking on rough surfaces.
- Used during cutting, welding, or fabrication work.
- Marking on black or dark-colored surfaces.
Scribing Block
A scribing block is a precision marking tool used for marking lines parallel to a reference surface such as a surface plate. It consists of a heavy base, an adjustable vertical spindle, and a scriber.
Description of Scribing Block
The base of the scribing block rests on the surface plate, while the vertical spindle holds the scriber. The scriber can be adjusted to different heights to mark lines on the workpiece. The tool allows accurate marking of horizontal lines at a fixed height.
Uses of Scribing Block
- Marking parallel lines on metal surfaces.
- Setting and checking the height of components.
- Layout work in fitting and machine shops.
- Used along with surface plates for precision marking.
Care and Maintenance of Scribing Block
- Keep the base clean and free from dust.
- Protect the scriber tip from damage.
- Apply light oil to prevent rust.
- Store in a safe place after use.
- Avoid dropping the tool to maintain accuracy.
Surface Plate and Auxiliary Marking Equipment
A surface plate is a precision flat plate used as a reference surface for layout, inspection, and measurement work. Surface plates are usually made from cast iron or granite and provide a perfectly flat surface for accurate marking operations.
Surface Plate
Surface plates are widely used in machine shops, inspection rooms, and tool rooms for precision layout work.
Types of Surface Plates:
- Cast Iron Surface Plate
- Granite Surface Plate
Uses:
- Layout and marking operations
- Inspection and measurement work
- Checking flatness and accuracy of parts
Care and Maintenance:
- Keep the surface clean and dry.
- Avoid placing heavy objects suddenly.
- Protect the plate from scratches.
- Cover the plate when not in use.
V Block
A V block is a precision tool used to hold cylindrical workpieces such as pipes or rods during marking and inspection operations. The V-shaped groove helps hold round objects securely.
Types of V Blocks:
- Plain V Block
- Clamping V Block
- Magnetic V Block
Uses:
- Holding round workpieces.
- Marking and inspection operations.
- Supporting cylindrical components.
Angle Plates
An angle plate is a precision tool used to hold workpieces at a right angle (90°) during marking, machining, or inspection. It is made from cast iron and has accurately machined surfaces.
Types of Angle Plates:
- Plain Angle Plate
- Slotted Angle Plate
- Adjustable Angle Plate
Uses:
- Holding workpieces at right angles.
- Supporting components during machining.
- Precision marking and inspection work.
Parallel Blocks
Parallel blocks are precision tools used to support workpieces at a uniform height above the surface plate or machine table. They are used in pairs to provide accurate and parallel support.
Uses:
- Supporting workpieces during machining.
- Maintaining accurate height.
- Used with machine vices and surface plates.
Accuracy of Auxiliary Marking Equipment
Auxiliary marking tools such as V blocks, angle plates, and parallel blocks are manufactured with high precision to ensure accurate marking and measurement. Their surfaces are ground and finished carefully to maintain dimensional accuracy.
Care and Maintenance
- Clean tools after use.
- Apply protective oil to prevent rust.
- Store tools properly in tool boxes or racks.
- Avoid dropping tools to maintain accuracy.
- Handle precision tools carefully.