Grinding Machine 5.1 Introduction Quiz

Grinding Machine

• Grinding is a metal cutting operation that removes metal in small volumes, using an abrasive wheel with many cutting edges.
• The machine on which grinding operation is performed is called a grinding machine.
• Grinding is done to obtain high dimensional accuracy and better appearance.
• The accuracy of grinding process is 0.000025mm.

Types of Grinding Machines

• Classified into two types: rough grinding machines and precision grinding machines.
• Rough grinding machines are used to remove stock without reference to accuracy.
• Main types of rough grinders: hand grinding machine, bench grinding machine, floor stands grinding machine, flexible shaft grinding machine, swing frame grinding machine, and abrasive belt grinding machine.
• Precision grinding machines are used to finish parts to accurate dimensions.
• Main types of precision grinders: cylindrical grinding machines, internal grinding machines, surface grinding machines, tool and cutter grinding machines, and special grinding machines.

Cylindrical Grinding Machines

• Used to grind external surfaces like cylinders, taper cylinders, faces, and shoulders of work.
• Two types: external cylindrical grinding machines and internal cylindrical grinding machines.

Surface Grinding Machines

• Used to finish plain or flat surfaces horizontally, vertically, or at any angle.
• Four types: horizontal spindle and reciprocating table type, horizontal spindle and rotary table type, vertical spindle and reciprocating table type, and vertical spindle and rotary table type.

Grinding Machine Operations

• Operations performed in a grinding machine: cylindrical grinding, taper grinding, gear grinding, thread grinding, and surface grinding.
• Cylindrical grinding: performed by mounting and rotating the work between centres in a cylindrical grinding machine.
• Taper grinding: done on long workpieces by swivelling the upper table.
• Gear grinding: done by generating process or using a form grinding wheel.
• Thread grinding: uses a grinding wheel shaped to the thread profile.

Grinding Wheel

• A multi-tooth cutter made up of many hard particles (abrasives) with sharp edges.
• Classified into three categories: solid grinding wheels, segmented grinding wheels, and mounted grinding wheels.
• Abrasives: used for grinding and polishing operations, having uniform physical properties of hardness, toughness, and resistance to fracture.

Abrasives

• Classified into two principal groups: natural abrasives and artificial abrasives.
• Natural abrasives: obtained from the Earth's crust, including sandstone, emery, corundum, and diamond.
• Artificial abrasives: silicon carbide abrasives and aluminium oxide abrasives.

Artificial Abrasives

• Silicon carbide: manufactured from silica, powdered coke, salt, and sawdust, used for grinding materials of low tensile strength.
• Aluminium oxide: manufactured from mineral bauxite, silica, iron oxide, titanium oxide, etc., used for grinding materials of high tensile strength.

Types of Bonds

• A bond is an adhesive substance that holds abrasive grains together in the form of grinding wheels.
• Different grinding wheels are manufactured by mixing hard abrasives with suitable bonds.
• Types of bonds: various, including vitrified, silicate, shellac, and resinoid.

Grain Size, Grade, and Structure

• Grain size (Grit): indicates the size of the abrasive grains used in making a wheel, or the size of the cutting teeth.
• Grade: refers to the hardness with which the wheel holds the abrasive grains in place.
• Structure: the relative spacing occupied by the abrasives and the bond, denoted by the number and size of void spaces between grains.

Standard Marking System of Grinding Wheels

• The Indian standard marking system for grinding wheels has been prepared to establish a uniform system of marking.
• The marking system includes: prefix, manufacturer's abrasive type symbol, type of abrasive, size of abrasive, grade of bond, structure of the grinding wheel, and type of bond.