Dressing and Truing 341

"Dressing and Truing" provides a guide to performing necessary grinding wheel preparations. Prior to using a grinding wheel, operators must visually inspect the wheel and perform a ring test to check for cracks, and then safely mount, true, balance, and dress the wheel. Each process has specific guidelines or goals, and each step is vital to the success of a grinding operation.

To perform dressing and truing properly, operators must first understand the wheel preparation process and its overall purpose. Mounting, truing, balancing, and dressing are crucial to the performance of the grinding wheel and to part quality. Improper dressing or truing can lead to poor surface finish, improper tolerances, scrapped parts, and wheel failure.

Class Details

Class Name:
Dressing and Truing 341
Description:
"Dressing and Truing" provides a guide to performing necessary grinding wheel preparations. Prior to using a grinding wheel, operators must visually inspect the wheel and perform a ring test to check for cracks, and then safely mount, true, balance, and dress the wheel. Each process has specific guidelines or goals, and each step is vital to the success of a grinding operation.

To perform dressing and truing properly, operators must first understand the wheel preparation process and its overall purpose. Mounting, truing, balancing, and dressing are crucial to the performance of the grinding wheel and to part quality. Improper dressing or truing can lead to poor surface finish, improper tolerances, scrapped parts, and wheel failure.
Version:
2.0
Difficulty:
Advanced
Number of Lessons:
16
Related 1.0 Class:
Dressing and Truing 230

Class Outline

  • Preparing a Wheel for Grinding
  • Inspecting a Wheel for Damage
  • Ring Testing
  • Mounting the Wheel
  • Wheel Preparation Review
  • Truing
  • Wheel Balance
  • Manufacturer Balancing
  • Detecting Wheel Imbalance
  • Balancing Methods
  • Truing and Balancing Review
  • Dressing
  • Dressing and Truing Tools: Stationary Dressers
  • Using a Single-Point Diamond Dresser
  • Dressing Tools: Rotary Dressers
  • Final Review

Objectives

  • Describe grinding wheel preparation steps.
  • Describe the ring testing process.
  • Describe the wheel mounting process.
  • Describe truing.
  • Describe wheel balance.
  • Describe how grinding wheel manufacturers ensure wheel balance.
  • Describe how to detect wheel imbalance.
  • Describe different methods for balancing a grinding wheel.
  • Describe dressing.
  • Describe common stationary dressing and truing tools.
  • Explain how to use a single-point diamond dresser.
  • Describe rotary dressers.

Job Roles

Certifications

Glossary

Vocabulary Term Definition
abrasive grain A small, hard particle that forms chips during grinding. Abrasive grains are held together by bond material to create grinding wheels and other abrasive tools.
American National Standards Institute ANSI. A private, nonprofit organization that administers and coordinates voluntary standards and systems for products, services, and systems in the United States. American National Standards Institute sets forth safety guidelines for the care and usage of grinding wheels.
ANSI B7.1 A standards document published by the American National Standards Institute that establishes guidelines regarding the safe use and care of grinding wheels and grinding machines. ANSI B7.1 includes requirements on wheel guards, wheel mounting, and flanges.
auto-balancing unit A precise, computerized device that detects vibration and corrects wheel imbalance. Auto-balancing units use counterweights, gases, or liquids to restore balance.
automated system A grinding wheel dressing system that operates without human action or intervention. Automated system settings are prepared during machine setup and require little in-process attention.
axis An imaginary straight line that passes through the center of an object. The axis of rotation of a grinding wheel after it has been properly trued is parallel with the machine spindle's axis of rotation.
balanced wheel A grinding wheel that has an equal distribution of weight about its dynamic center of rotation. A balanced wheel's center of rotation should be aligned with the wheelhead spindle's axis of rotation.
balancing The process of ensuring that a grinding wheel has equal weight about its center of rotation. Balancing a grinding wheel helps to achieve accurate grinding results.
balancing stand A frame-like device with two equal points that can hold a mounted grinding wheel. A balancing stand is often used to check the static balance of a grinding wheel.
bearings A friction-reducing device that allows one moving part to glide past another moving part without excess wear or friction. Bearings in the wheelhead spindle on a grinding machine help to support the grinding wheel.
blotters A pair of paper or cardboard rings that help prevent the flanges from damaging the bond material in a vitrified bond grinding wheel. Blotters are only required for grinding wheels with vitrified bonds.
bolts An externally threaded, cylindrical fastener with a head at one end and a threaded blunt end at the other. Bolts are designed to fit into nonthreaded holes to join parts and are assembled with a nut.
bond material The adhesive substance in a grinding wheel that holds the abrasive grains together. Bond material determines the grinding wheel's hardness.
bonded abrasive An abrasive tool made from a combination of abrasive grains and bond material. Bonded abrasives are typically in the form of grinding wheels but also include dressing sticks.
bore The interior diameter of a cylindrical object. The bore on a grinding wheel is its center hole.
carat A unit of weight for precious stones. Carats can be used to measure the weight of diamonds.
centerline An imaginary line that defines the theoretical center of an object. The vertical centerline on a grinding wheel is a reference point when performing a ring test.
chatter marks A type of surface flaw on a workpiece that looks like waves or lines. Chatter marks are often the result of vibrations from an out-of-balance or out-of-true wheel.
clearance An intentional amount of space left between two components. Clearance between the bottom of the grinding wheel bore and the spindle is provided by wheel manufacturers.
CNC Computer numerical control. The use of computers, programs, and motors to automatically control tool movement and carry out sequences of machining operations. CNC grinding machines require an operator for setup, but the machine movement is controlled through automatic or computerized actions.
computer numerical control CNC. The use of computers, programs, and motors to automatically control tool movement and carry out sequences of machining operations. Computer numerical control grinding machines require an operator for setup, but the machine movement is controlled through automatic or computerized actions.
concentric Having a common center or sharing the same axis with another object. A concentric grinding wheel is aligned with the spindle's axis of rotation.
continuous dressing A dressing process that requires a rotary dresser to maintain constant contact with the grinding wheel during grinding. Continuous dressing is performed using diamond roll dressers.
control unit A component of a computer's central processing system that directs its operation. A control unit on an auto-balancing unit directs counterweight movement to restore dynamic wheel balance.
conventional abrasive The category of abrasive materials that includes the most commonly used, inexpensive abrasives. Conventional abrasives include aluminum oxide and silicon carbide.
counterweights A weight that provides balance against something of equal weight. Counterweights are used with an auto-balancing unit to restore the dynamic balance of a grinding wheel.
crush roll A hard rotary dresser used under pressure to form a profile into the operating surface of a grinding wheel. Crush rolls are often made of tungsten carbide or tool steel.
cylindrical grinder A machine used to grind round, tapered, or angled features on a cylindrical workpiece. Cylindrical grinders can be automatic or manual.
defects An irregularity in the specified and expected composition of a part. A defect can impair functionality and, in the case of a grinding wheel, may cause an accident or serious injury.
diameter The distance from one edge of a circle to the opposite edge. The diameter of a circle is twice the length of its radius.
diamond The hardest known substance. Diamond is both a naturally occurring and a manufactured superabrasive.
diamond roll dressers A hard rotary dresser that is used for continuous dressing. A diamond roll dresser is typically used to dress superabrasive wheels.
dresses The process of removing swarf, dull grains, and excess bond material from a grinding wheel by fracturing away the wheel surface. Dressing can also condition the wheel for specific grinding operations.
dressing The process of removing swarf, dull grains, and excess bond material from a grinding wheel by fracturing away the wheel surface. Dressing also conditions the wheel.
dressing stick A rectangular abrasive tool used to remove swarf and dull grains from the operating surface of a grinding wheel. Dressing sticks are bonded abrasive tools.
dynamic balance When a grinding wheel is balanced at full wheel speed as part of the wheel system, flanges, and spindle while it is on the grinding machine. Dynamic balance can be tested during grinding but is usually performed between grinding operations.
electroplated A superabrasive bond type created by immersing a metal wheel in an electrically charged chemical bath that contains metal particles. Electroplated wheels have a single layer of superabrasive material.
fasteners A device that holds two or more objects together. Common fasteners include bolts and screws.
finishing A grinding process that achieves the required size and surface finish of the part. Finishing operations require precisely balanced wheels.
flange A flat or raised metal disc that clamps down on the top and bottom sides of a grinding wheel. A flange should be at least one-third the diameter of the grinding wheel.
fracture The breaking apart of an abrasive grain into two or more pieces as a result of stress. Fracturing can occur when individual grains break away from the wheel bond or when very small pieces of a grain break off.
friction A force that resists motion between two objects in contact with one another. Friction generates heat between the two contacting objects.
grinding fluid A liquid used during grinding operations to clean, cool, and lubricate the grinding wheel and workpiece. Grinding fluid helps to prevent a loaded or clogged grinding wheel.
imbalance An uneven distribution of weight around a rotating object. Imbalanced grinding wheels can cause machine vibration.
magnetic chuck A workholding device that holds a workpiece or tool during grinding. Magnetic chucks can be permanent or electromagnetic.
mass The amount of matter in an object. Mass gives an object weight when it is acted upon by gravity.
material removal rate The amount of material removed from a workpiece in a given amount of time, measured in cubic inches per minute or cubic millimeters per second. Material removal rates fluctuate depending on the type of abrasive in the grinding wheel, speed settings, and other factors.
mounting A process that uses flanges to prepare a grinding wheel for placement on the wheelhead spindle. Mounting occurs after an operator inspects a grinding wheel for damage.
nonmetallic A material such as plastic or ceramic that is not made from metal. Nonmetallic materials can be very high in tensile strength.
nut A fastener containing a hole and internal threads that mates with a screw or bolt. A nut may be used to secure a flange to a grinding wheel.
Occupational Safety and Health Administration OSHA. The federal agency that enforces workplace safety and health legislation in the United States. The Occupational Safety and Health Administration helps employers reduce injuries, illnesses, and deaths in the workplace.
operating surface The outer edge of a grinding wheel. The operating surface, or periphery, of a grinding wheel is usually the portion that contacts the workpiece.
out-of-balance wheel A grinding wheel with an unequal distribution of weight about its dynamic center of rotation. An out-of-balance wheel's center of rotation is not parallel or concentric with the spindle's axis of rotation.
parallel Two lines or objects that are equidistant from each other and will never intersect. Parallelism between the workpiece and grinding wheel assures grinding accuracy in surface grinding.
periphery The outer edge of a grinding wheel. The periphery, or operating surface, of a grinding wheel is usually the portion that contacts the workpiece.
personal protective equipment PPE. Safety equipment that machine operators wear or use to prevent injury in the workplace. Personal protective equipment includes safety glasses and safety boots.
pores An opening or void in a material. The pores in a grinding wheel facilitate effective grinding fluid application.
porosity The relative number of openings or voids in a material. The porosity of a grinding wheel can be filled in by the wheel manufacturer when balancing the wheel.
profile A workpiece feature created by a specialized grinding wheel. The profile on a grinding wheel has to be precisely dressed so the shape can be ground into a flat or cylindrical workpiece.
radially Movement that is perpendicular to the workpiece centerline. A radial feed of a crush roll into a grinding wheel is used to form a grinding wheel for profile grinding.
relieved flange A flange that is recessed on one side to take pressure away from the center hole of the grinding wheel. Relieved flanges can be used with many different wheel types.
resin bond A type of grinding wheel bond material made from synthetic plastic resins. Resin bond grinding wheels with superabrasives require separate truing and dressing processes.
ring test A manual method of inspection that technicians use to detect cracks in a grinding wheel. A ring test is performed before mounting a vitrified bond grinding wheel.
rotary dresser A very precise dressing and truing tool that turns as it conditions a grinding wheel or alters its shape. Rotary dressers can form an entire profile onto a grinding wheel in one short plunge operation.
rotary dressers A very precise dressing tool that turns as it conditions or alters the shape of a grinding wheel. Rotary dressers are often motorized.
roughing A type of material removal process with a high material removal rate. Roughing processes grind a workpiece close to its finished size but without regard for surface finish.
self-dressing A method of wheel dressing where pressure or feed during grinding forces abrasive grains to break off the bond material in varying degrees. Self-dressing reveals a sharper abrasive grain.
setup The series of tasks necessary to prepare for processing a workpiece. Setup includes preparing machines, adjusting workholding devices or tooling, and safeguarding machine elements to ensure proper and safe operation.
single-point diamond dresser A dressing and truing tool that contains an individual, industrial-grade diamond embedded on one end. Single-point diamond dressers are common stationary dressing and truing tools.
sleeve flange A flange that consists of two differently shaped parts that fit around a grinding wheel to deflect mounting pressure. Sleeve flanges are generally used with larger and wider grinding wheels used for precision grinding.
spindle A rotating component of a machine tool. The spindle on a grinding machine wheelhead holds the mounted grinding wheel.
spindle nut A type of nut that screws onto a threaded bolt. A spindle nut holds a mounted grinding wheel on the grinding machine spindle.
static balance The ability of a grinding wheel to remain at rest in any position when placed on a balancing stand. Static balance means that a grinding wheel has no heavy side.
stationary dresser A dressing tool that has a single fixed point or multiple fixed points. Stationary dressers include single-point diamonds and abrasive dressing sticks.
stresses A force that attempts to deform an object. Stresses in grinding operations include rotational and thermal.
structure The spacing of the grains and bond material in a grinding wheel. Structure depends on the method used to create the porosity within the grinding wheel.
superabrasive A group of relatively expensive but effective materials possessing superior hardness, abrasion resistance, and thermal conductivity. Superabrasives used in grinding wheels are cubic boron nitride and diamond.
surface finish The texture of a part after it has gone through the grinding process. Surface finish is key to the performance of a completed part.
surface grinder A grinding machine used to finish workpiece surfaces or grind parts to accurate size. Surface grinders may have vertical or horizontal machine spindles.
swarf The gritty combination of chips, abrasive grains, and worn bond material produced during grinding. Swarf can clog a grinding wheel and cause it to function improperly.
tailstock A component on a cylindrical grinder located opposite the headstock that supports the far end of the workpiece. The tailstock holds the stationary diamond dresser.
tile dresser A metal stationary dressing and truing tool with a thin blade saturated with diamonds. A tile dresser lasts longer than a single-point diamond dresser.
tolerances The allowable deviation from a given dimension that will still allow the part to perform its desired function. Tolerances indicate the allowable difference between a physical feature and its intended design.
tool steel A specialized type of alloy steel that exhibits excellent strength, toughness, and wear resistance. Tool steels can be used to make crush roll rotary dressers.
traverse rate The speed at which the dressing tool travels across the periphery of a grinding wheel. The traverse rate during dressing is critical in order to achieve the desired surface condition for the grinding wheel.
truing The process of removing material from a grinding wheel to make the wheel periphery perfectly round. Truing a wheel makes the wheel periphery run true to the axis of rotation of the grinding machine spindle.
tungsten carbide A sintered compound of tungsten and carbon bound together in a cobalt binder. Tungsten carbide is used to make crush roll rotary dressers.
vitrified bonds A clay or ceramic grinding wheel bond material characterized by its strength, rigidity, and resistance to oils, water, and temperature changes. Vitrified bonds have qualities similar to glass.
washers A flat, thin disc used with a threaded fastener to relieve friction or distribute pressure. A plastic washer is often used between a vitrified bond grinding wheel and a flange.
wheel failure When a grinding wheel breaks into pieces while rotating. Wheel failure can result in serious injury.
wheel glazing The formation of a smooth, flat surface on the periphery of a grinding wheel. Wheel glazing can occur when grinding a hard workpiece with a hard grinding wheel.
wheel guards A protective cover secured over the grinding wheel on a grinding machine to protect machine operators from broken wheels or debris. Wheel guards should maintain alignment with the wheel throughout the grinding process.
wheel infeed The depth of the grinding wheel into the workpiece. Wheel infeed is a grinding variable that can significantly alter the surface condition of a wheel.
wheel speed The speed of the periphery, or edge, of the grinding wheel as it rotates. Wheel speed changes depending on the wheel type and grinding operation.