Grinding Machines

Introduction

    Grinding is a process to make something sharp or smooth by rubbing it on a rough hard surface which is also known as “hot work“. Whereas grinding in the manufacturing / construction or whatever industry is a process (with the help of particular machine) of removing a layer of metal surface which releases physical hazards (i.e. noise, vibration, heat, etc.).

    A grinding machine, often shortened to grinder, is a power tool or machine used for grinding. It is type of machining using an abrasive wheel as the cutting tool. Each grain of abrasive on the wheel’s surface cuts a small chip from workpiece by shearing deformation. 

    In industries grinding is used to finish workpiece that must show high surface quality and high accuracy of shape and dimension. It has some roughing applications in which grinding removes high volumes of metal very rapidly. Grinding machine’s speed is approx. 2000-3000 revolutions per minutes (RPM).

Working Principle

    A grinder is just like an electric motor (a portable power tool) which supplies motion power to the grinding wheel (abrasive wheel) using pulley and belt. For the portable grinder, there is a rotor inside grinding machine and the power switch is located beside the handle of grinding machine. 

Types of Grinding Machine

• Belt Grinder: Belt grinder is an abrasive machining process used on metals and other materials. It is typically used a finishing process in industry. A belt is coated in abrasive material, is run over the surface to be processed in order to remove materials or produce the desired finish.

• Bench Grinder: A bench grinder is a benchtop type of grinding machine used to drive abrasive wheels. A pedestal grinder is a similar or larger version of grinder that is mounted on a pedestal, which may be bolted to the floor or may sit on rubber feet.

• Cylindrical Grinder: The cylindrical grinder is a type of grinding machine used to shape the outside of an object. The cylindrical grinder can work on a variety of shapes; however, the object must have a central axis of rotation. This includes but is not limited to such shapes as a cylinder, an ellipse, a cam, or a crankshaft.

• Surface Grinder: Surface grinding is done on flat surfaces to produce a smooth finish. It is a widely used abrasive machining process in which a spinning wheel covered in rough particles cuts chips of metallic or non-metallic substance from a workpiece, making a face of it flat or smooth.

• Centerless Grinder: Centerless grinding is a machining process that uses abrasive cutting to remove material from a workpiece. It in-feed centerless grinding is used to grind workpieces with relatively complex shapes, such as hourglass shape.

• Tool & Cutter Grinder: A tool and cutter grinder is used to sharpen milling cutters and tool bits along with a host of other cutting tools. It is an extremely versatile machine used to perform a variety of grinding operations i.e. surface, cylindrical or complex shapes, etc.

• Jig Grinder: Jig grinder is a machine tool used for grinding complex shapes and holes where the highest degree of accuracy and finish are required. the jig grinder is very similar to a jig borer, in that the table positioning and spindles are very accurate.

• Gear Grinder: Gear grinders are finishing machines that use a grinding wheel rotating at high speed to grind the surface of the gear (workpiece) teeth. Gear grinders can be broadly divided into continuously generation grinder and profile grinders.

• Die Grinder: Die grinders and rotary tools are handheld power tools used for grinding, sanding, honing, polishing, or machining material. 
  
  

•  Angle Grinder: Angle grinder, also known as a side grinder or disc grinder, is a handheld power tool used for grinding and polishing. Although developed originally as tools for rigid abrasive discs, the availability of an interchangeable power source has encouraged their use with a wide variety of cutter and attachments.

Safety Precautions

1. Ensure Toolbox Talk on grinding machine to be provided by Safety Officer / Supervisor.
2. Inspect for any cracks, damage or wheel out of round in/on grinding wheel and discs on portable grinder, before use.
3. Ensure ‘Work Permit‘ prior work commence.
4. Before mounting a grinding wheel on a grinder, checks the operative speed marked on the grinder and rate a speed of a grinder wheel to ensure safe working practices.
5. Never adjust the work rest or tongue guard while the grinding wheel is in motion.
6. Allow the wheel to develop its full speed before beginning work to avoid unsafe acts.
7. Do not stand directly in front of any grinder when first starting it up which is considered as horseplay.
8. Never force the stock into the wheel of a fixed grinder whether motor slows down. 

• Ensure that the wheel is properly dressed at all times.
• Store grinding wheels (both used and unused) in properly in a safe place.
• Machines must be shut off when unattended to avoid near misses.
• Suitable protection hoods or guards must be provided all times.
• All tools and accessories shall be kept properly arranged near machines.
• Employees shall use all proper PPEs.
• Eye protection i.e. fixed vision type guard rigidly attached above the wheel itself, and goggles / spectacles should always be used.