USE AND MAINTAIN A PEDESTAL GRINDER
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CODE:
USE AND MAINTAIN A PEDESTAL GRINDER
CODE: MG
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1. MODULE OBJECTIVE
To enable the learner to use a pedestal grinder safely and correctly.
2. LEARNING OBJECTIVES
On completion of this module, the learner must be able to -
2.1 Inspect and maintain a pedestal grinder.
2.2 Use a pedestal grinder safely and correctly to grind objects, e.g. twist drills and tool bits.
3. ASSESSMENT AND EVALUATION CRITERIA
3.1 A practical test will be set at the end of the module and must be completed without using references.
3.2 The learner will be required to use a pedestal grinder to grind a twist drill. The following standards must be achieved:
(a) The grinder must be inspected and maintained to the standards set in this module.
(b) The sharpened drill must meet the following standards:
· The point angle of the drill must be according to the gauge.
· The clearance angles must comply with the list of angles supplied.
· The lip lengths must be equal.
(c) All safety rules must be adhered to.
4. 
ADDITIONAL RESOURCES
4.1 Demonstrations by a competent person.
4.2 MIETTB training video: Hand Tools Part II
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DICTIONARY
Spindle: Pin or axis that revolves or on which a thing revolves.
Tungsten: Steel-grey heavy metallic element with very high melting point, used for alloying steel.
Dress: Finish a surface off.
Chisel: Tool having square bevelled end for shaping wood, stone or metal.
Shank: Shaft of a tool, e.g. drill bit, between head/body and handle.
Taper: To gradually narrow or thin at one end.
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HAZARD IDENTIFICATION AND CONTROL (HIAC) FORM
MG
USE AND MAINTAIN A PEDESTAL GRINDER
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STEPS IN OPERATION / PROCESS
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POTENTIAL ACCIDENT / INCIDENT
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CONTROLS (BY RESPONSIBLE PERSON)
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1 Adjust and maintain a pedestal grinder
2 Use a pedestal grinder
3 Use hand tools
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ITEM / TASK
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DESCRIPTION
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 1. Construction
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1.1 The grinder consists of an electric motor with a grinding wheel mounted on each end of a spindle & (FIG. 1). For general purposes one wheel is usually a coarse grained wheel for the fast removal of metal, while the other is a fine grained wheel for finish grinding.
FIG. 1
1.2 In a machine shop one wheel usually has a greenish colour and is used for grinding tungsten & tipped tools. The other is a medium grained greyish colour wheel and is used for grinding high-speed tools.
1.3 On the ordinary pedestal grinding machines, i.e. those which are usually used for grinding tool bits, drills, etc., provision is not made for cooling the work during grinding. However, a water container into which the tool may be dipped, is provided. This water must be free from soluble oil.
1.4 When the grinding wheel reaches the stage where it is worn to the diameter of the spacer pads, or when the tool-rest is at its extreme, and there is excessive clearance between the rest and the wheel, the wheel must be replaced.
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2. Inspect and maintain a pedestal grinder
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2.1 Before using a pedestal grinder it must be inspected for the following, and any faults discovered must be corrected:
· Make sure the grinder is isolated.
· Condition of grinding wheel - must not be obviously chipped or cracked. Replace if necessary.
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ITEM / TASK
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DESCRIPTION
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· Wheel must be secured properly.
· The tool rest must not be more than 1 mm from the wheel and parallel to the wheel. Adjust if necessary.
· The wheel is not loaded or glazed. Dress the wheel if necessary. (See later in this module).
· Switch on and check if the wheel runs true. If not, switch off and correct.
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3.   Safety rules when grinding
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3.1 The machine must be isolated prior to any adjustment being made to the machine.
3.2 The operator’s standing area must be free from any lubricant and loose material to prevent slipping or tripping, which may result in the operator falling onto the moving part of the machine.
3.3 The operator’s hands must be free from oil or grease to prevent the slipping of the work piece in his hands.
3.4 Loose fitting clothes must not be worn as it may be caught in the moving part of the machine.
3.5 Closed safety glasses must be worn when grinding to protect the operator’s eyes.
3.6 The operator must stand aside and let the wheel run until it has reached maximum speed for a short period of time, before beginning to grind.
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SELF TEST 1
1. Name the aspects that must be inspected before using a pedestal
grinder.
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2. Name six safety rules to observe when using a pedestal grinder.
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Check your answers against the module notes or given answers (where applicable). If they are correct, ask your Training Officer to sign off your work. The Training Officer will spot check your work before signing.
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2. DRESSING A GRINDER WHEEL
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ITEM / TASK
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SAFE WORK PROCEDURE
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1. Trouble shooting
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1.1 Wheel is loaded:
· When non-ferrous metals such as aluminium, copper, etc., are ground on a grinder they will clog the pores of the wheel and prevent it from cutting.
· This condition is indicated by pieces of metal being embedded in the surface of the wheel.
1.2 If the surface of the wheel develops a smooth, shiny appearance, it is said to be glazed.
· This indicates that the wheel is blunt and will not cut properly.
NOTE: When either of the above conditions appear or when the cutting surface of the wheel is not running true or is not flat, it can be corrected by dressing the wheel.
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2.  Procedure for dressing a wheel
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2.1 Your Training Officer will demonstrate how to dress a grinding wheel. Refer to FIG. 2.
FIG. 2
The back of the tool-rest must be straight. If it is not straight and in good condition, the wheel will take the shape of the rest.
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ITEM / TASK
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DESCRIPTION
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NB: Always wear safety glasses when working on a grinding machine.
2.2 Take notes while your Training Officer demonstrates how the wheel is dressed:
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3. USE A PEDESTAL GRINDER TO SHARPEN A TWIST DRILL
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ITEM / TASK
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DESCRIPTION
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1. Introduction
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1.1 Learning to sharpen a twist drill will teach you two important things that you will need in your career.
· How to operate a pedestal grinder safely and correctly.
· The correct way of sharpening a drill bit - something that an electrician uses quite often.
1.2 Firstly, the construction of a twist drill will be considered. Refer to FIG. 3.
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2. Construction of a
twist drill
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2.1 The point is the cone shaped end that does the cutting and consists of the following:
· The chisel & edge which is the exact centre of the axis of the drill. The sharp edge at the extreme tip of the drill should be dead centre.
· The lips which are the cutting edges of the drill.
· The flank, which is the portion of the point back from the lips or cutting edge.
· The lip clearance which is the amount the surface of the point is relieved back from the lips.
2.2 The shank
· Twist drills are made with shanks that are either straight or tapered &.
· Straight shank drills are held firmly in adjustable drill chucks.
· Taper shank drills have shanks that are tapered in the “Morse Taper” standard.
· These tapers range from No. 1 to No. 5 and these drills can fit directly into drill spindles with “Morse Tapers”, or can be adapted to fit by using tapered sleeves (sockets).
· On the taper shank is a tang. This tang fits into a slot in the spindle sleeve or socket, and assists to disengage the two tapers from each other.
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ITEM / TASK
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DESCRIPTION
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2.3 The body is the portion between the point and the shank (refer to FIG. 3) and consists of:
· The flutes, which are two or more spiral grooves that run the length of the drill body. The flutes do four things, namely,
- They help form the cutting edge of the drill points,
- They curl the chips tightly for easier removal,
- They form channels through which the chips can escape from the hole being drilled, and
- They allow the coolant and lubricant to get down to the cutting edge.
· The land (margin), which is the narrow strip extending back the entire length of the flute. It is the full diameter of the drill.
· The body clearance which is the part of the drill body that has been reduced in order to cut down friction between the drill and the wall of the hole.
· The web which is the metal column that separates the flutes. It gradually increases in thickness towards the shank to give added strength.
FIG. 3
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ITEM / TASK
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DESCRIPTION
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NB: The smaller range of twist drills are normally obtained with straight shanks and are commonly know as “jobber series” drills. See FIG. 4.
FIG. 4
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   3. Off-hand sharpening of drills
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3.1 Sharpening procedure (see Figs. 5 and 6).
Ask your Training Officer to demonstrate this procedure.
FIG. 5
FIG. 6
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ITEM / TASK
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DESCRIPTION
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· Visually check the existing angles of the cutting edges and decide whether they are correct, or establish the amount of error.
· Support the drill approximately 40 mm from the tip with one hand and grasp the shank of the drill with the other.
· Position the cutting edge of the drill to the wheel in such a way that it is parallel with the face of the wheel.
· Position the fingers nearest the tip of the drill on the tool-rest and lightly touch the cutting edge of the drill onto the wheel.
· Apply light forward pressure on the drill. Using the tool-rest as the point of pivot, lower the hand grasping the shank of the drill at the same time turning the drill clockwise slightly to give lip clearance. See FIG. 4.
· Release the pressure and return the drill cutting edge parallel with the face of the wheel.
· Dip the drill into water frequently to avoid overheating.
· Repeat the above steps approximately four times.
· Keep the hand at the tip of the drill stationary and rotate the drill until the second cutting edge is in position for grinding.
· Repeat the grinding stages until wear is removed.
3.2 Checking the lip angle using a grinding gauge.
See FIG. 7.
FIG. 7
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ITEM / TASK
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SAFE WORK PROCEDURE
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· Position the drill against the gauge and bring the cutting edge up to coincide with the angle on the gauge.
· Visually check that the lip angle is the same as the gauge (included angle of 118 degrees).
· Turn the drill to position the second cutting edge to the gauge and visually check the angle.
· Correct any error by grinding it on the machine.
NB: Lips at different angles will cause an oversize hole.
3.3 Checking the drill point corners on a gauge.
· Smear the gauge with chalk.
· Position the drill on the drill gauge centre pin to support it.
· Touch the lip on the back face of the gauge, and scribe a line (FIG. 8).
FIG. 8
· Turn the drill through 180 degrees and scribe a line with the second lip. This line should coincide with the first line if both cutting edges are of the same length.
· Correct any error by grinding.
NB: Lips of different lengths will cause an oversize hole (FIG. 9).
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ITEM / TASK
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DESCRIPTION
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FIG. 9
3.4 Thinning the point. See FIG. 10.
Ask your Training Officer to demonstrate this procedure.
FIG. 10
· Grasp the drill with both hands, with one hand near the point of the drill.
· Position the back edge of one side of the web to the corner of the grinding wheel.
· Apply light pressure to the drill and thin the point.
NB: Ensure that the drill cutting edge does not touch the grinding wheel.
· Repeat the operation on the other side of the web.
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PRACTICE
Practice sharpening a twist drill.
Ask your Training Officer to check your work and to sign you off when it is correct.
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You have now completed Module
If you feel ready, ask for the assessment for the module.
