Using Lathes for turning operations QPEO2/011N

Performing Engineer Operations Level 2

Using Lathes for turning operations QPEO2/011N

Using Lathes for turning operations

A lathe is a machine, which is used to remove material from the work piece to the required shape and size.

A turned component

The Centre Lathe

1Saddle hand wheel – used to move the saddle of the lathe along the bed allowing cuts to be made along the length of the bar in the z axis.

2 Automatic feed engagement lever – engages the automatic feed for facing or turning along diameters.

3 Main on/off lever – the central position is ‘off’ and the lever is lowered for ‘forward’ and raised for ‘reverse’.

4 Half nut engagement lever – used in conjunction with the lead screw to cut threads.

5 Cross feed hand wheel – used to move the cross slide to face ends and change the depth of cut.

6 Spindle speed control levers – changes the speed of rotation of the machine spindle.

7 Emergency stop – stops the machine in an emergency.

8 Tool post and tool holder – holds the tool in the correct place ready for machining.

9 Compound slide – can be swivelled to machine tapers or chamfers.

10 Automatic feed direction control – used to change the tool direction from facing to surfacing along the work.

11 Tail stock is used to support the work piece and provide a holding device to mount cutting tools such as a drill chuck or collet.

12 Coolant pipe and tap provide a method of directing coolant on to the tool and work piece.

Arrive in the workshop wearing the correct PPE

Under the Health and Safety at Work Act 1974, it is the law that appropriate clothing must be worn in engineering workshops.The correct PPE will allow you to work safely and ensure you are protected against hazards in the workplace.

Safety GlassesWorkshop Overall (no short sleeves)Safety BootsHair Net for Long Hair Barrier Cream

Arrive in the workshop wearing the correct PPE

It is important that overalls are the corrected size and are not baggy or have parts that could get caught on equipment. Long hair must be tied back or a hairnet worn to reduce the change of becoming entangled in moving parts. Where gloves are not worn barrier cream should be applied to hands instead to protect them. To protect yourself from dangers such as:- dermatitis on your hands

safety glasses to prevent swarf and coolant getting into your eyes

Safety boots to guard against heavy falling objects

Overalls to protect your clothes from coming into contact with oil, cutting compound, coolant and swarf. It may also reduce the risk of entanglement.

Working safely in the workshop

When working in the workshop you need to be mindful of the safe working practises in the workshop. This is to include wearing the correct PPE and following the instructions on operation sheet. You would have been shown/trained/instructed to carry out a safety check and other tasks before using the lathe in the workshop. It is important that you must only use tools / equipment that have been show how to use and do so in a safe manner. If you are unsure about how to do something or use a machine, you must always seek help from your supervisor.


You will be trained to carry out tasks in the workshop so that you can work to the best of your abilities and develop you skills safely. It is good to show initiative when learning new skills however you should only act on your own initiative if you have been shown/trained/instructed how to do something and are confident in your abilities of performing task safely. If you are unsure about how to do something or use a machine, you always seek help from your supervisor.

Checking a lathe before use

Check that the power is isolated and that the chuck is secure on the spindle and that there is nothing inside the spindle nose unsecured, such as a piece of waste bar. Ensure that the coolant is turned off and the nozzle is directed to the base of the machine. Check that the guards are secure and that no automatic feeds are engaged before turning on. You should also make sure the chuck key is not left in the chuck.

Using the lathe axis’s

To be able to control the hand wheels efficiently, test by turning the hand wheels to different measurements. With each movement, examine the ease of handling the hand wheel and setting the dial. This way, you can get a feel of working and controlling the hand wheels and dials before you actually begin using the lathe to cut the material on the workpiece.

Setting up in a tool post before cutting takes place

Check that the tool is sharp or the tip is in good condition and clamp the tool firmly in the tool holder. Put the holder in position and set the tool tip to centre height. Align the tool so that it has clearance on the side and front face before using. Some tools will do this automatically if set perpendicular to the machine axis.

Positioning and securing work holding devices to the lathe machine spindle.

• Before starting make sure the area is clean with particular attention to the spindle and chuck surfaces. The bed of the machine must be protected with a piece of wood placed near the headstock to prevent damage.


Before starting make sure the area is clean with particular attention to the spindle and chuck surfaces. The bed of the machine must be protected with a piece of wood placed near the headstock to prevent damage.

When positioning and securing the chuck into the headstock spindle you must ensure that location marks line up with each other and registration marks are in the correct positon.

There are three markings next to these bolts, a straight line and two V's. These markings as well as the notch on the bolt are used to tell if the chuck is attached or not. As above, when the notch is in between the two V's the chuck is correctly tightened. The notch can change exactly where it is between these two V's but as long as it is between them, the chuck is properly mounted. To loosen the bolts and remove the chuck you turn the bolt counter clockwise until the notch aligns with the straight line. When the notch on the bolt and the straight line are in alignment then the chuck can be removed from the lathe.


During manufacturing, the jaws are ground to fit a specific chuck, so are not interchangeable with other chucks of the same size.

Looking at the front of the chuck with the jaws removed, you can see the scroll thread that engages the jaw teeth. If you slowly turn the chuck key in one of the key holes, you can see the leading edge of the chuck scroll pass by the slot for the jaw.

This leading edge of the scroll must engage with the first tooth of each jaw in turn, in the correct sequence, to properly reseat the jaws. If the jaws are installed out of sequence, the tips of the jaws will not meet at the centre of the chuck.


As long as the jaws are installed in the sequence 1, 2, 3 they will meet in the middle. However, depending on which slot you start with, there actually are three different configurations that could be chosen. For optimum alignment of the jaws, it is best to install the jaws in the slots in which they originally were shipped.

Installing the jaws is easiest with the chuck mounted on the spindle so that each slot can be rotated to a convenient working position to insert the corresponding jaw.


Back off the scroll thread in a clockwise direction until it is just to the right of the jaw slot #1. Press jaw #1 into the slot until it stops against the scroll. Now, while pressing down on the jaw with your thumb, turn the chuck key clockwise to advance the scroll counter clockwise to engage the scroll with the first tooth of the jaw. Continue until the leading edge of the scroll is just to the right of the second slot. Insert jaw #2 and repeat for jaw #3. If you got it right, all 3 jaws should meet evenly in the middle of the chuck if you crank them all the way in.

Checks to made on the work piece location

Using a dial test indicator (DTI) the workpiece can checked to see if it is running true to the machine axis. Tighten or losing the jaws to adjust the position of the workpiece making sure that the travel in the DTI is within the tolerance specified. A final tightening up of all jaws, using an equal force on the chuck key and check again with the DTI before starting machine.

Before cleaning down a lathe at the end of a session

First of all isolate the lathe from the power supply then remove the cutting tool from the tool post. Finally, take out the workpiece and any tooling in the tailstock before cleaning down.

Safety feature used on this lathe

The yellow painted areas show that a safety feature is being used on this lathe.

The lathe is fitted with a headstock chuck guard covering the machine spindle.

The machine has a curtain guard attached to the saddle and both ends of the bed. This is to cover the Leadscrew and prevent entanglement.

The tailstock is fitted with a dead stop dowel in the frame of the machine to prevent the tailstock leaving the bed when moved.

The emergency stop button is tagged with a yellow disc so that it is easier recognised.

Safety when using a lathe

Safety when using a lathe

All sideways and longitudinal movement must have freedom of movement. The machine guard must be used at all times when the chuck is rotating. Wear good fitting overalls. Loose sleeves can catch on rotating work and quickly pull your hand or arm into the machine. Wear safety shoes to protect your feet from sharp metal chips on the shop floor, tools and heavy items that may get dropped. Remove wrist watches, necklaces, chains, rings and other jewellery. Tie back long hair so it can't get caught in the rotating work.Always double check to make sure your work is securely clamped in the chuck or between centres before starting the lathe. Make sure the feed is disengaged before starting the machine. Start the lathe at low speed and increase the speed gradually. Remove the chuck key immediately after use. Keep your fingers clear of the rotating work and cutting tools. A machine safety check sheet must be completed before commencing work on the lathe and you should always consider other peoples safety around you before carrying out a task.

Machinery Checklist

Lathe Faults

The lathe machine faults maybe discovered in the first instant, by carrying out the machine safety check sheet. Each point is physically inspected and checked on the lathe and surrounding area. Further faults can be recognised on the lathe by use your senses.First proceed to identify a problem using your eye sight; being able to see a problem with the machine is far safer and reduces risk of harm or damage to the machine because this can be done at the beginning with the machine turned off.

Listening to the machines sounds as its running for any unfamiliar sound it doesn’t normally make. Also you can use the sense of touch, if the machine is violently vibrating you will be able to feel it on your hands which also means something is very wrong.Another way of identifying a problem can be through the use of smell; being able to smell something burning or smoke would mean there is something is wrong and you should turn the machine off straight away and tell your supervisor about the problem.

The Working Area

Students will prepare the work area and ensuring that it is in a safe condition to carry out the intended activities. It is essential to keep the work area free from hazards and special care must be taken when using hazardous materials, fluids, heavy equipment and the removal of swarf.

The lathe should always be left cleaned with the machine isolator turned off after use.Students must place completed work in the correct location, returning drawings and work instructions to the carousels, tools and equipment returned to the stores in their designated location, removing any swarf and waste materials to be disposed of line with the organisations environmental requirements.

Any defects or damage to the tools and equipment used must be reported to the supervisor or technician.

This must all be completed so that it is ready for the next student to carry out their machine safety check sheet. This avoids the risk of the next user endangering themselves on left over swarf, sharp drills left in drill chucks, untreated coolant spillages. Tools and equipment must be returned to stores and chemicals placed in a COSHH locker.

The Working Area

Working areas must be kept clear.

The Working Area

Machines must always be turned off before cleaning and tools removed to prevent injury.

Checking tools

It is your responsibility to check tools BEFORE USE

Many tools have sharp cutting edges (turning tools, drills, parting of tools and profiling tools) and must be handled with care to avoid injury or damage to the tool. It is important to choose the correct tool for the job taking into account the material being cut and the type of operation required. Once the tool has been chosen it must be inspected for any visible signs of damage to the cutting tool such as: - missing teeth, blunt tools, craters, built up edges, cracks, discolouration, signs of rubbing etc.

Always test the tool works before starting the activity using a trial cut and at the end of the activity inspect it for any damage before returning it to the stores. Some cutting tools become dull after a long period of use and need to be re-sharpened. Ask the technician and he will sharpen it for you.

Check tools before use for broken or blunt cutting surfaces

Trial Cuts

• A trial cut is where you cut a slightly smaller diameter than your starting piece and measure it using a micrometer. Using the axis dial on the hand wheel you’ll set it to zero and then turn the hand wheel to cut a small amount off the diameter and then check it again with a micrometer to make sure it is the same amount of material being taken off the diameter of the work piece. If the two match the operator can feel confident about proceeding with further cuts to produce the correct size on the work piece.

Handle and store tools safely

To handle tools correctly and safely you must hold the tool with the sharp end pointing downwards and always walk when carrying them. You must be carefully and not rush when loading and retrieving tools from the machine to prevent injury or damage. Storing your tools safely and correctly is managed by putting them back in the stores or toolbox where they have come from. Some tools you have acquired have designated areas such as named draws or boxes to be returned too.

Obtain the appropriate job documentation

Before starting the job, students need to obtain the appropriate job documentation which includes component drawing, operation sheet, machine safety check list and specification sheet. It is important to always check drawing, check operation sheet, listen to instructions to avoid mistakes.

Obtain the appropriate job documentation

Collect the laminated drawings and operation sheets from the carousel racks in the workshop or the secure fire retardant cupboards. Some specification sheets will be provided by your tutor.

Reference points

These are geometric points, planes, datum edges and lines from which subsequent measurements will be taken. In machining you establish reference points to help you build reliable fixtures to hold and gauge your parts, an example would be to use one edge through the whole job to clamp against, that edge never changes so all measurements are in relation to that fixed edge and this would become the reference point. It can also be a hole corner etc., it is important that it remains constant throughout the process.

Interpret imperial and ISO metric systems of measurement

• International Standard Organisation defined the units used for measurement described as the “Systeme International” or SI. These are the definitive references of guidelines for use of SI units and tables of conversion factors.

• • A single numeric conversion factor is associated with each simple

unit. The conversion factor is the number by which a quantity expressed in that unit must be multiplied in order to be expressed in the equivalent unit in the standard system of units.

• If the conversion factor for a metre is 1.0, while the conversion factor for foot is 0.3048 since 1 foot = 0.3048 meter. The conversion factor for a numeric constant is just the constant itself.


Metric – Metres, Centimetres, Millimetres. Micro metreImperial – Yards, Feet, Inches, Fraction inch To convert Imperial to Metric - Multiply the Imperial figure by 25.4 to give the metric equivalent. Despite efforts to 'turn metric', there are still many imperial units in use today. For example do you know your height in centimetres and your weight in stones and pounds?Do you cycle for 5 miles but run 100 metres? It is therefore helpful to know how to convert between the two.


Converting from one metric unit to anotherThe most common metric conversions are between mm, cm, m and km.For example:

1 cm = 10mm1 m = 100cm = 1000mm1 km = 1000 m = 100 000cm = 1 000 000mmkilo means 1000, so 1 km = 1000 mcenti means 1/100th, so 1cm = 1/100th mmilli means 1/1000th, so 1mm = 1/1000th m

Converting units of mass and capacityFor example:

1 km = 1000 m, so 1 kg = 1000 g1 m = 100 cm, so 1 l (litre) = 100 cl (centilitres)1 m = 1000 mm, so 1 g = 1000 mg (milligrams)

Limits of size

There must always be some allowance, however slight, for size on components. This allowance is usually stated in the title block as limits, the general allowable deviation for all dimensions; if special limits are needed for particular dimensions, they must be inserted separately. The correct term for this allowance is the limits of size, often called the limits. There are always two limits to represent the maximum and the minimum permissible size to which any component feature can be made. General limits of size are shown on engineering drawings in the title block and they refer to all dimensions. Any feature that has other limits than those indicated in the title block is indicated as shown by one of the methods on the next slide..

Tolerances

All the above examples show a feature of diameter 10 mm. The finished component must have a diameter between 9.5 mm and 10.5 mm for it to be acceptable. The names of the component parts that make up the dimension are:

the nominal size; it is the nearest whole millimetre (or fractional inch) size of the feature; it is 10 mm in the examples above.

the maximum permissible size; this is called the high limit (or top limit); it is 10.5 mm in the examples above.

the minimum permissible size; this is called the low limit (or bottom limit); it is 9.5 mm in the example above

The tolerance, which is the difference between the limits of size, is 1 mm in the examples above, that is the difference between 9.5 mm and 10.5 mm.

Speeds and Feeds

This data needs to be extracted from the drawing along with information on the order of steps from the operation sheet. Effective planning of operations on machines needs to take place by calculating speeds and feeds required by machines before starting operations. Cutting Speed: Cutting speed is the distance travelled by the work surface in unit time with reference to the cutting edge of the tool.The cutting speed, S is simply referred to as speed and is expressed in m/min. Feed: The feed is the distance travelled by the tool into or along the workpiece each time the tool point passes a certain position in its travel over the surface.In case of turning, feed is the distance that the tool travels in one revolution of the workpiece and is called the feed rate which is measured in mm/rev Depth of cut: It is the distance through which the cutting tool is plunged into the workpiece surface.It is the distance measured perpendicularly between the machined surface and the un machined (uncut) surface or the previously machined surface of the workpiece.The depth of cut d is expressed in mm.

Cutting speed in metres per minute for the material to be cutm/min

Speeds and Feeds

Cutting speed in metres per minute for the material to be cut

S = Aluminium 100m/min Workshop poster

Calculating the machine speed

The information required for material cutting speed is located on various notice boards throughout the workshop. The material which is being cut, the diameter of the workpiece/cutting tool and depth of cut will affect your selection of cutting feeds and speeds.

Materials to be used: Ø15mm Aluminium x 30mm long bar x 2 Formula for machine spindle

Speed: S x 1000 = RPMπ x D

S = Material cutting speeds:- Aluminium 100 m/min1000 = conversion to mmπ = 3.14D = diameter of bar or diameter of rotating cutting tool (i.e. drill or milling cutter)

100 x 1000 = 100000 = 2123.14 RPM 3.14 x 15 47.10

Centring the tool in the tool post

Before starting any turning activity it is most important to check that the point of the lathe tool is centred. This means that the lathe tool point should be the same height as the tip of the tailstock centre. If this is not done and the tool point is either above or below the centre point usually the finish to the work piece being turned will be poor. Also, a significant amount of vibration could take place during turning operation giving dimensional errors along the edge of the work piece being cut.

Tool and fixed centre in the tailstock How the position effects the tool

The tool is adjusted by moving the carriage up or down in the tool post until it is in line with the centre in the tailstock. The tool post can be moved to aid positioning of the cutting tool to get an improved view of the tool tip to the tip of the centre.

Types of turning operations

Facing A cut is made across the end of the metal to make it right angles to the axis and produce a workplace datum. A right hand cutting tool can be used for this, the tool moving from the outside of the work to the centre removing any marks from cutting. Special facing tools are available that have a larger radius on the cutting edge allowing the tool to take larger cuts.

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Parallel Turning

Cutting along the metal, parallel to its axis, to reduce its diameter. Where possible arrange the smallest diameter on your right pointing towards the tailstock. This allows long cuts to be made using the right handed turning tool. Always turn the largest diameter down to size first if possible.

Direction of tool

Tapering

There are four ways or producing a taper on the lathe:-with a form tool with a tapered surface to cut short.using a taper turning attachment.setting the tailstock out of line with the machine axis. adjusting the compound slide to the required angle (see below).

The angle can be changed by losing the nuts or alan key bolts located on either side of the compound slide and by moving the slide reading the angle off the protractor scale to the required position. Then retighten the bolts.

Parting Off

When the part is finished it is best to re-move it in a similar way to facing the ends. First check the tool is on centre as any error will put extra strain on the tool. Use a slower speed than calculated (50% reduction).

The parting tool must be moved in slowly using automatic feed if possible or by hand feed with a smooth feed to prevent the tool digging in. As the tool cuts deeper in to the work piece the tool must be pulled out and moved to the side to make the cut wider to stop the tool sticking and breaking.

Direction of tool

1. Types of tool cuts: roughing and finishing cuts

• Roughing cuts are deep tool cuts using a fast feed to bring down the diameter of the workpiece to the rough size which is specified on the operation sheet or engineering drawing. By removing a lot of material quickly it reduces the amount of time needed to produce the workpiece.

• A Finishing cut uses a fine feed rate and shallow cuts to leave a good finish. They are used to cut accurate cuts to produce the correct diameter within the limits or tolerance set by the operation sheet or engineering drawing.

The Effects of Various Cuts

There are a lot of areas to consider when producing different size cuts with, material properties being the most foremost, correct cutting conditions concerning the tool/depth of cut, surface speed of the tool and the coolant being used.

Tool life relies on maintaining the correct relationship of the above conditions.

Shallow cuts will increase the tool life due to the tool working below its optimum performance. Less wear on the tool because of a small cutting force is generating very little heat on the tip of the tool. The shallow cut will produce a good finish because of the reduced force required for the tip of the tool to cut and be able to cut accurately to the required limits or tolerance specified.

Large or roughing cuts can generate a lot of wear due to the increased of the cutting forces on the tip of the tool producing excessive heat. This will cause a tarring action on the material being turned and will lead to a poor finish. The cutting tip of the tool will become dull and less effective reducing the tools life and so will need to be sharpened more often to maintain dimensional accuracy.

Cutting fluids and compounds

Cutting fluids are used to keep the work piece and cutting tool at a stable temperature. These fluids, often referred to as coolants, are an essential part of most machining or chip making processes. An example of what can be used in the workshop are soluble oils, also called Chemical emulsions – They are mixed with water and typically contain other additives to aid in maintaining work surface integrity. The quality of the water used is critical to optimum performance. Being mixed with water, the soluble oils have less lubrication qualities but are a more efficient in their cooling ability.They perform several functions including:

• Cooling work and tool surfaces• Removal of chips from the cutting area• Contributing to longer tool life• Promoting part surface integrity• Aiding in corrosion control

Cutting fluids and compounds

The method of fluid/coolant application can directly affect chip formation, chip removal, cutting tool life, and the surface finish of the work piece.

The quality of the surface finish is very much dependant on how well the fluid reduces tool-to-work piece friction and its ability to dissipate heat. Without a cooling fluid the work piece may be affected by the generation of heat causing distortion and fluctuation in dimensional accuracy in the work piece.

Cutting compounds like green treflex are used for tapping/die cutting threads and reaming; along with hard white tallow used for fixed centres on lathes to prevent wear, aid lubrication and promote tool life. These compounds are in a solid form at room temperature and can be brushed on to the tool.

Operated in both hand and power modes

Manual and Automatic feed. Z Axis and X Axis can be operated in two modes.

Operated in both hand and power modes

When operating the lathe manually there are two hand wheels that you’ll be using for the majority of the time to control the direction of the cutting tool. One hand wheel controls the movement in ‘X’ direction across the bed, which has an effect on the size of the diameter you are cutting. The other hand wheel controls the movement in ‘Z’ direction, which is the longitude and is used to control the length you are cutting.

Auto feed

There is a diagram on the apron next to the directional plunger to indicate the position of the plunger to activate the direction of travel required. This is then engaged using the feed lever.The auto feed in the ‘X’ across the bed is selected by push in the plunger for the direction of travel and engaging the feed lever. The auto feed in the ‘Z’ longitude direction is selected by pulling out the plunger for the direction of travel and engaging the feed lever. Care must be taken using the auto feed with the operator being mindful of the task being undertaken and the direction of the tool when being engaged to prevent damage to the workpiece. The operator must remain focused on the task at all times with particular attention to the position of the tool/tool post to the chuck on the headstock. This is to avoid a possible collision or entrapment.

How does the Auto Feed workView of the Apron on the front of the Saddle

‘X’ Cross Slide Hand wheel

Lead Screw

Lathe Bed

Start lever

Feed Rod ‘Z’ Longitude Hand wheel

Directional plunger

A feed rod is a round, keywayed shaft that runs the length of the bed, usually alongside the screw cutting shaft. This shaft is driven from the lathe spindle, via the tumbler gears, connecting gears, and the headstock gearbox. Which one is rotated is set with a lever on the box.This box allows adjustment of the turn’s ratio between the spindle and the feed rod, when sliding and surfacing operations are being done on the lathe.

Auto feed

The saddle contains a gear which slides along the feed rod, containing a key that engages the drive from the keyway in the feed rod (or shaft). It also contains two mechanical clutches, that engages the feed shaft rotation to either the saddle hand wheel shaft, or the cross feed screw on the cross slide. By engaging it to the hand wheel shaft, the saddle is fed along the bed by the pinion and fixed gear rack attached under the bed, directly under the slide ways at the front of the lathe. While the spindle is revolving, the feed shaft is revolving, and if either the cross or longitudinal clutches are engaged, the saddle moves along the bed or the cross slide moves across the bed, depending on which clutch is engaged. The distance either moves (per revolution of the spindle) is set in the headstock gearbox. If reverse direction feed is needed, the tumbler gears are used to reverse the direction of rotation of the feed shaft. The feed rate is selected by using gear position levels on the head stock.

Acme Lead Screw Headstock Gearbox

Provides themovement in three axes as well asthe screw cutting drive on most lathes.

Restarting the lathe after an emergency

To stop the machine in a normal situation the start lever on the saddle should be used and the feed lever must be disengaged before carrying out further operations. However if any other emergency stop device is used it must reset after use. An example would be if the spindle guard was removed the lathe would stop and it would need to be replaced before continuing.

In an emergency situation, there are several options that can be used. The treadle brake will turn off the power and apply a brake to the machine spindle to stop it; the start lever on the saddle and the red emergency stop button will also turn off the power. You should only use the emergency stop devices in an emergency to prevent miss use and unnecessary wear.

The procedure for restarting the lathe after an emergency would be to turn off the power (machine power isolation switch) and complete a safety checklist.

However before this can be carried out the machine must be made safe. This can be done by following this sequence of procedures: - isolate the machine, turn off the automatic feed, return the start lever to its neutral position and investigate and remove the problem safely.

Extracting information from engineering documentations

An engineering drawing contains information about the shape of a component. It also shows dimensions regarding the sizes and limits to which the component should be manufactured. Information regarding dimensions must be clear and in accordance with BS 8888,

British Standard 8888

For the use with technical drawing, symbols; abbreviations are used in engineering terminology to make documents clearer and less confusing. It is a common language that engineers can understand and communicate with each other around the world.

First and third angle projection

Before reading an engineering drawing it is important that you have understood how the component has been draw on the sheet. There are range of drawing layouts are available to present different types of information in the most descriptive way.

Zeus book is a reference and data chart book.

It supports the engineering drawing and operational sheet by providing addition information so that the Job came be made within the specified tolerances. The book contains 28 pages contain data on standardised drill sizes and decimal equivalents, details of all popular threads, tapping and clearance drills, UNF, UNC, BSF, BSW, Metric coarse and fine, hardness comparison tables, jig boring co-ordinates for equally spaced holes, allowances for sheet metal bending and Morse tapers. It also contains tables for sine, cosine, tangents and cotangents.

Ø 5mm tapping drill is required to drill the hole before tapping.

Lathe Three Jaw chuck Clamping

• Standard three jaw chucks use three points of contact to secure the work piece. It allows you to work efficiently and safely as the holding device prevents the material from coming out of the chuck causing harm.


To properly install the work piece, clean and remove any swarf from jaws as this will cause damage when caught between the jaws and the workpiece. Twist the workpiece as the jaws are tightened so that the workpiece locates in the centre of the chuck. Before cutting, spin the chuck to visually check that the work piece has securely located on the machines axis properly.

Clamps are most effective when placed as near as possible to the cutting action without interfering with the movement of the tool doing the cutting. Check the tool path before starting to cut as the tool will cut the machines as easily as the work and if the cutting operation is through the work be mindful of what the tool will be cutting into.

Often, parts have features which can be undesirable to clamp in a 3 jaw chuck.

forces are present, a live centre could be used depending on the operation.


Often, parts have features which can be undesirable to clamp in a 3 jaw chuck.

Notice the tapered section of the part shown. Rather than clamping on the tapered section, it is desirable to clamp onto the straight portion immediately before the taper.Care must be taken when parts have a large overhang. If large side cutting

The effects of clamping

Clamping in compression (metal-on metal-on-metal) causes the minimum distortion. Consider using clamping intermediates like brass shim stock to save surface finish. Over clamping can cause elastic distortions of the work which leads to loss of accuracy as well as damage to finished surfaces. Severe over clamping crushes the work piece. Under clamping will let the work fly out of the chuck and may could cause serious harmThe final finish on the work piece could be badly scratched, dented, maybe distorted and not reach the required dimensional accuracy of the drawing.

Component checks

Checks that should be made before removing your component from the machine are:-

Ensure that all tasks have been completed from the operation sheet.

Check for dimensional accuracy making sure they are within tolerance.

All features have been produced including chamfers.

Surface finish is to the required specification from the drawing and spec sheet.

Does the work piece require parting off.

The material isn’t hot and there are not any sharp edges.

Cutting Tools

The basic tool geometry is determined by the rake angle of the tool.The rake angle has two major effects during the metal cutting process.One major effect of rake angle is its influence on tool strength. A tool with negative rake will withstand far more loading than a tool with positive rake. The other major effect of rake angle is its influence on cutting pressure. A tool with a positive rake angle reduces cutting forces by allowing the chips to flow more freely across the rake surface.

Cutting Tools

Cutting Tools

The importance of the clearance angle to prevent rubbing

Cutting Tools

Rake angles should be increased for soft materials (e.g. aluminium) and decreased for hard materials (e.g. high-carbon steel). The side rake angle and the top rake angle combine to form the effective rake angle. Front Clearance tool angle (8º for most materials) Side Clearance tool angle (6– 8º for most materials)

Problems with turning activities

This usually happens when the cutting tool has not been set properly. Before you begin working, always check the cutting tool installed on the metal working lathe and make sure that it is placed right in the centre. The proper positioning of the cutting tool is important to ensure that the cuts are made accurately. As you cut the metal, the tip of the cutting tool may become heated due to friction. Give the equipment frequent breaks so that the tools cool off and the chuck does not rotate at a speed that cannot be controlled.

The tailstock of the metal working lathe may not be fixed properly. Although the tailstock does not have any specific purpose, it has to be locked down properly before the chuck can be fed into the metal. If the tailstock remains loose, the metal may not be cut properly. To tighten the tailstock, inspect the screws closely, and if they are loose, tighten them properly

Manual and auto feed.

It is important to know how to move the cutting tool in the longitudinal and cross feed directions on the machine. Moving the cutting tool over the material is something that needs to be mastered in order for the tool to work efficiently producing the required finish with dimensional accuracy. Knowing how to engage and disengage the auto feed handles to create the correct feed needs to be planned to prevent damage to the workpiece and machine.

Hazard with swarf build up

Stop the machine and isolate it from the power. Using a swarf rake, pair of pliers or tough gloves, remove the swarf and put it in the scrap bin. Do not handle swarf with your bare hands as it can be very sharp.

Backlash in machine slides and screws

Backlash is any non-movement of the lead screw that happens during axis reversals. This happens due to the loss of motion in machine parts because of a wear gap between the leading and trailing thread edges which are functioning parts in the machine slides and screws. If the X axis is moved 25mm in the positive direction; then immediately after this movement is moved in the negative direction. If any backlash exists in the X axis, then it will not immediately start moving in the negative direction, and the motion departure will not be precisely 25mm. wrong measurements being made and leading the workpiece to be wrong and you would have to start again.

Backlash in machine slides and screws

ACME Thread showing wear in the thread causing a gap between the leading and trailing edges of the thread.

This can be prevented by ensuring the x axis is moved in one direction only on to the required measurement or if an error occurs the x axis is turned two turns away from the dimension required and then two turns back to the target measurement.

The lathe has developed a fault

Do not use it. Isolate and padlock switch.

Making sure it is clearly labelled with a ‘do not use’ sign and report it to your supervisor or trainer.

Accidents

Hazards you can have with the turning tools include; it could be possible to injure yourself on the sharp tools when setting the machine or cleaning the machine this can be overcome by being extra careful around the tool and could take the tool out before cleaning the machine. Other hazards would be entanglement, swarf thrown off the machine, coolant spillage. To overcome these problems’ you can wear the correct fitting overalls to reduce the chance of entanglement, Wear safety glasses to stop swarf from being thrown off the machine and landing in your eye, Coolant spillages must be cleaned up straight away so that it prevents slipping and endangering other people.


When working in the workshop, be mindful of the safe working ;--practises in the workshop, to include wearing the correct PPE and following instruction from your supervisor. It is also very important to fill out machine safety check list before commencing work on any machines and be aware of people around you who are also carrying out work.

You will be trained to carry out tasks in the workshop so that you can work to the best of your abilities and develop you skills safely. It is good to show initiative when learning new skills however you should only act on your own initiative if you have been shown/trained/instructed how to do something and are confident in your abilities of performing task safely. If you are unsure about how to do something or use a machine, you always seek help from your supervisor.

Using Lathes for turning operations QPEO2/011N

Education

Transcript of Using Lathes for turning operations QPEO2/011N