The document provides information on safe working practices for using abrasive wheels. It discusses the characteristics of abrasive wheels including the material, grain size, grade, grain spacing, and bond type. It outlines several hazards associated with abrasive wheels such as breathing dust, electric shock, and flying fragments. The safety procedure for mounting an abrasive wheel is described which includes checking the wheel for damage, ensuring the guard is in place, and wearing proper eye protection. Warnings are provided such as not using equipment with faulty guards and making sure to wear eye protection when grinding.

1. SAFE WORKING
PRACTICES:
ABRASIVE WHEEL
Presentation Prepared by:
Efren Echague

2. I. Introduction
 An Abrasive Wheel is a wheel consisting of an abrasive particles
bonded together with various substances. They are mounted to
Grinding Machine before it can be used for the work intended for
them.
 The wheels are generally made from a matrix of coarse particles
pressed and bonded together to form a solid, circular shape. Various
profiles and cross sections are available depending on the intended
usage for the wheel. They may also be made from a solid steel or
aluminium disc with particles bonded to the surface.
SAFETY IN USING ABRASIVE WHEELS

3.  A grinding machine, often shortened to grinder, is any of various
power tools or machine tools used for grinding, which is a type of
machine using an abrasive wheel as the cutting tool, Each grain of
abrasive on the wheel's surface cuts a small chip from the workpiece
via shear deformation.
 Grinding is used to finish work pieces that must show high surface
quality (e.g., low surface roughness) and high accuracy of shape and
dimension.
 Manufacture of these wheels is a precise and tightly controlled
process, due not only to the inherent safety risks of a spinning disc,
but also the composition and uniformity required to prevent the disc
from exploding due to the high stresses produced during rotation.

4.  Characteristics of an Abrasive Wheel
There are five characteristics of an Abrasive wheel: material, grain size, wheel
grade, grain spacing, and bond type. They will be indicated by codes on the
wheel's label.
1. Material
The actual abrasive material, is selected according to the hardness of the
material being cut.
• Aluminum Oxide(A)
• Silicon Carbide (S)
 Ceramic (C)
 Diamond (D, MD, SD)
 Cubic Boron Nitride (B)
Grinding wheels with diamond or Cubic Boron Nitride (CBN) grains are
called super abrasives. Grinding wheels with Aluminum Oxide
(corundum), Silicon Carbide or Ceramic grains are called conventional
abrasives.
2. Grain Size
Grain size, from 8 (coarsest) 1200 (finest), determines the physical size of the
abrasive grains in the wheel. A larger grain will cut freely, allowing fast cutting
but poor surface finish. Ultra-fine grain sizes are for precision finish work.
3. Wheel Grade
Wheel grade, from A (soft) to Z (hard), determines how tightly the bond holds
the abrasive. Grade affects almost all considerations of grinding, such as
wheel speed, coolant flow, maximum and minimum feed rates, and grinding
depth.

5. 4. Grain Spacing
Grain spacing, or structure, from 1(densest) to 16 (least dense).
Density is the ratio of bond and abrasive to air space. A less-dense
wheel will cut freely, and has a large effect on surface finish. It is
also able to take a deeper or wider cut with less coolant, as the chip
clearance on the wheel is greater.
5. Bond Type
How the wheel holds the abrasives, affects finish, coolant, and
minimum/maximum wheel speed. There are two main types of
bonding agent: inorganic and organic. See example with Specs. on
next 2 slides.
◦ INORGANIC BOND ORGANIC BOND

6. ◦ Inorganic bonds are mainly vitrified, ie the wheel is generally
fired in a furnace to give the bond a hard, strong but brittle
structure. These wheels are used for precision grinding
applications as they hold their shape, but require dressing.

7.  Organic bonds are not fired but are cured at low temperature; the
bond agents are resinoid (B), rubber (R) and shellac (E). Such
wheels are tough, shock-resistant and self-dressing, and are most
suited to non-precision applications, for example fettling (trimming or
cleaning rough edges) and cutting off.

9. Example of Bonded Abrasive Wheel with Complete Label

10. II. Several Uses of Abrasive Wheel
◦ Grinding of Surface for welding preparation (e.g. Beveling, surface
cleaning)
◦ Grinding of welded joints to clean out excess metals or to cut-out
welded joint
◦ Grinding of work pieces that must show high surface quality (low
surface roughness and high accuracy of shape and dimension
◦ Surface reduction
◦ Cutting
◦ Sharpening of Tools
◦ Various uses in manufacturing Jewelries, Stone works and metal
works
III. Hazards in using Abrasive Wheels
Grinding wheels can pose many health and safety hazards:
 Health hazards:
◦ Breathing in dusts caused by grinding can cause respiratory
problems.

11. • Compressed air (used on air-powered grinders) can cause body
injury due to its high pressure.
◦ Vibration can cause feeling of discomfort even after work.
◦ Noise can damage hearing and be stressful.
◦ Electric shock can kill.
 Safety hazards
◦ A wheel that shatters can seriously injure the operator and those
working or passing nearby.
◦ Shooting fragments of a wheel can injure the eyes and face.
◦ Contact with a wheel can cause cuts and scrapes.
◦ If a portable grinder drops, it can injure the legs and feet.
◦ Sparks can cause skin burns, and fire.

12. IV. Safety Procedure –Mounting an Abrasive Wheel (Lee Engineering
HSSE Handbook Section 6.14)
 No person is permitted to mount, change or dress abrasive
wheels/disc, unless trained, competent and authorized. Prior to use
always ensure that the guard is in place and the wheel is in good
condition.
 The following procedure should be followed when mounting an
abrasive wheel:
 Ensure that the wheel/disc you are using is appropriate to the
material that you are grinding.
 Use only tools issued by the supplier for changing wheels/disc.
 Always wear eye protection to the correct standard.
 Keep the work area neat and tidy.
 Ensure that the power to the tool (Grinder) is OFF.
 Clean the abrasive wheel with brush and check for any signs of
damage
 Under no circumstance should a damage wheel be used.
 Check that the spindle bearing is not worn.
 Check that the maximum abrasive wheel speed is greater than the
maximum spindle speed of the grinder.

14. V. Warnings:
 Do not use Equipment with faulty or missing guards
 Do not mount, change or dress wheels/disc unless you are suitably trained, competent
and authorized.
 Always wear Eye protection (Eye Goggle or Face Shield) when grinding
 Stop the Machine if abnormal vibration was noticed during operation, disconnect it
from power source and check for wheel damage and worn bearing.
 Pay attention to the Job (Grinding) you are doing and do it safely.
 Do not leave the Grinder while it is running.
 Make sure that the Grinder Switch is in OFF position before plugging it in an outlet.
VI. Abrasive Wheel Expiration:
Safety requirements for bonded abrasive products, with type of bond B (Resin) and BF
(Resin/Reinforced) for use on hand-held grinding machines or hand-held cutting-off
machines shall be marked with a date of expiry. The date of expiry shall at the longest
be within 3 years from the date of manufacture. It is expressed as month and year e.g.
04/2009.
Reccomendation (St Gobain Norton –Abrasive Disc Manufacturer); Resinoid Bonded
grinding wheels be used up within 2 years from the date of manufacture. This
recommendation assumes that Resinoid Bonded grinding wheels have been stored
under ideal storage conditions.
These same comments also apply to rubber and shellac bonded grinding wheels. As
for vitrified or glass bonded grinding wheels, the shelf life is less influenced by humidity
and adverse storage conditions as compared to resinoid, rubber or shellac, but even
vitrified grinding wheels do not have an infinite shelf life. The best procedure and the
best rule of thumb is to have any wheel that is two years old or older re-speed tested
and re-inspected to ensure it is fit for use.

15.  Even when a grinding wheel is tested and equipped with all
possible safety devices, grinding is still a hazardous activity. It is
important to always follow below safe working practices:
 Safety goggles or safety spectacles shall be worn by all
personnel exposed to grinding operation (ILL.3)
 Where necessary, additional personal protective equipment shall
be used, such as face protection, ear protection,
respiratory devices, aprons, protective footwear, and protective
gloves (ILL.3).
 Never wear loose clothing, ties, rings or other jewelry.
 Keep long hair in a hair net.
 Let the machine run at full speed for one minute while everyone
stands clear.
VI. Safety at Work:

16.  Bring the workpiece slowly and smoothly into contact with the
wheel (don’t bump the wheel). Bring a cold wheel a chance to
warm up.
 Don’t force work against the wheel so that the motor slows down
excessively or stalls.
 Don’t side grind on the flat side of a straight wheel; use wheels
designed for this purpose (ILL. 4).
 If a grinder appears to be defective or unsafe, tag it and report
the problem immediately to your supervisor.
~END OF PRESENTATION~