This document discusses centreless grinding. It begins by introducing centreless grinding as a grinding process that removes fine amounts of material from a workpiece without using centers or chucks to hold the workpiece. It then discusses the mechanism of chip removal in grinding and the composition of grinding wheels, including types of abrasives and bonds. The document outlines the main types of centreless grinding and notes that centreless grinding is suitable for grinding long cylindrical bars in bulk and can generate different diameters and tapered surfaces. It concludes by stating that centreless grinding provides a surface roughness value ranging from 6.3 to 0.25 micrometers.

1. CENTRELESS
GRINDING
GRINDING MACHINE
1
BISHAL DAS
BT14MEOOI

2. CONTENTS
▸ Introduction
▸ Mechanism of chip removal
▸ Grinding wheel composition
▸ Types of abrasives and bonds
▸ Types of centerless grinding
▸ Surface roughness value
2

3. INTRODUCTION
Grinding is a process carried out with a grinding wheel made up of
abrasive grains for removing very fine quantities of material from the
workpiece surface.
Used When
▸Machining hard materials,which are not possible with other processes
▸Close dimensional accuracy
▸High degree of surface smoothness(Ra=6.3 to 0.25)
3

4. CHARACTERISTICS OF GRINDING
▸ Variable and indeterminate geometry of the grits
▸ A random orientation of the grits giving unknown orientation.
▸ High grinding velocity
4

5. INTERACTIONS
1. Grit-workpiece interaction
2. Chip-bond interaction
3. Chip-workpiece interaction
4. Bond-workpiece interaction
5

6. GRIT-WORKPIECE INTERACTION
6

7. CHIP ACCOMMODATION IN GRINDING
7

8. WHEEL COMPOSITIONAL SPECIFICATIONS
51 A 60 K 5 V 05
▸ 51-Manufacturer’s mark to identify the right kind of abrasive used
▸ A-Grit material
▸ 60-Grit Size
▸ K-Hardness of the wheel
▸ 5-Structure of the wheel
▸ V-Bond type
▸ 05-Manufacturer’s identifier
8

9. TYPES OF ABRASIVES
AL203
‣ with defect structure
‣ free cutting action
‣ fine tool grinding operation
‣ grinding of heat sensitive ferrous materials
SiC-
‣ Harder but less tough than AL2O3
‣ Reactive with iron and steel
Diamond-
‣ Super abrasive,high chemical resistance and
‣ low coefficient of thermal expansion
CBN
‣ Hardness next to diamond and synthetically produced
‣ less reactive with hardened steels,hard chill cast iron,nickel base and cobalt based super alloys.
9

10. BOND TYPES
▸ Vitrified bond-Clay mixed with fluxes,strong,rigid and porous,called ceramic
bond
▸ Silicate-Sodium silicate(NaSiO3),Less sensitive to shocks
▸ Synthetic resin-Thermosetting resins,good strength but not heat and chemical
resistant
▸ Rubber-Natural/synthetic rubber,flexible
▸ Shellac-Very high surface finish is achieved
▸ Metal-High thermal conductive metals(copper and aluminium alloys),the grit
will be used till fully utilised.
10

11. TYPES OF GRINDING MACHINES
▸ Cylindrical grinding for generating cylindrical surfaces
▸ Surface grinding for generating flat surfaces
▸ Centreless grinding for generating axi-symmetrical shapes
11

12. CENTRELESS
GRINDING
▸ Automatic feed is provided.
▸ No support required(head
stock,tailstock)
▸ Suitable for long cylindrical bars
▸ Used for production in bulk
▸ Can grind different diameter workpiece
and taper surface also.
12

13. 13

14. SURFACE FINISH VALUE

15. GECAM_ BELT CENTERLESS GRINDING MACHINE For round pieces.mp4