06Lathe Accessories PDF - Manufacturing Processes for Metals

Bachelor of Science in Technology Management TechM 215 - Manufacturing Processes for Metals 1st Semester 2021-2022 Lathe Machine Accessories Intended Learning Outcomes: 1. Identify and state the function of each accessory 2. Set up each lathe machine accessory 3. Observe...

Bachelor of Science in Technology Management TechM 215 - Manufacturing Processes for Metals 1st Semester 2021-2022 Lathe Machine Accessories Intended Learning Outcomes: 1. Identify and state the function of each accessory 2. Set up each lathe machine accessory 3. Observe the highest standards of safety Topics: 1. Head Stock Accessories 2. Lathe Carrier 3. Tailstock Centers 4. Steady Rest  Head Stock Accessories TYPES OF SPINDLE NOSES There are four types of headstock spindle noses to which accessories are fitted. They are: Threaded Spindle Taper and Locking Pin Cam Lock Bolted  Head Stock Accessories Threaded Spindle Many older and most small lathes are provided with spindle noses which have an external thread. Accessories are screwed directly on to the spindle. The fit of the thread holds the accessory true to the axis of the spindle. A shoulder bears against the accessory to hold it square to the spindle.  Head Stock Accessories Taper and Locking Ring The accessory is located on a tapered spindle and driven by a key When a threaded locking ring is rightened the accessory is firmly held in the taper. A “C” type spanner is used to tighten and loosen the locking ring.  Head Stock Accessories Cam Lock A flange on the headstock spindle has a number of holes to receive cam lock studs projecting from the rear face of the accessory. When the cam locks are tightened, the accessory is drawn firmly on to a short taper and against a flange.  Head Stock Accessories Bolted The accessory is bolted to a flange on the spindle by a number of studs that protrude from the rear face of the accessory. A short taper locates the accessory centrally. A short taper locates the accessory centrally. Drive is provided by a locating key.  Mounting Accessories on the Spindle Take care when mounting or removing accessories from the headstock spindle. Damage could affect the accuracy of both the accessory and the spindle. The following points should be observed. Never use power to mount or remove accessories from threaded spindles. The used of force may jam the accessory and damage the thread. Switch of the power to the driving motor before fitting accessories to the spindle. Clean the spindle and the mating parts of the accessory to ensure accurate location. Chip or dirt jammed mating parts will cause the accessories to run out of true. Permanent damage will occur if the chips are embedded into the locating surface.  Head Stock Accessories Place a wooden cradle block between the accessory and the lathe bed. The cradle will support the accessory while it is being fitted, and will protect the bed from damage. Remove accessories from the spindle by reversing the procedure used to fit them.  TYPES OF ACCESSORIES The accessories fitted to the headstock spindle are used for holding or driving the work. The accessories are: The Drive Plate The Face Plate Chucks The Headstock Centre  TYPES OF ACCESSORIES The Drive Plate The plate is used to drive work that has been set up between centres. The plate rotates the work. It does not support it in any way. A lathe carrier is used to connect the work with the plate.  TYPES OF ACCESSORIES The Face Plate The face plate is used to hold and drive work that cannot be held between centres or in a chuck. Slots in the face plate allow the work to be bolted in position. Counter balances must be used when large work is mounted out of centre on the face plate.  TYPES OF ACCESSORIES Chucks Chucks are work holding devices, which grip work of various size and shape by means of adjustable jaws. There are many types of chucks used. The most commonly used are: The three jaw self-centering chuck The four jaw independent chuck  The Three Jaw Self-Center chuck This chuck is used to hold round or hexagonal work. A chuck key is used to rotate a scroll that moves the three jaws simultaneously. Generally, two sets of jaws are provided. One set is used for holding work externally. The other set is for holding work internally. The jaws are marked and must be fitted in the correct order to maintain the self-centering feature of the chuck. The chuck is easily distorted when gripping irregular work such as castings, black and hot rolled steel or when taking heavy cuts. To maintain accuracy, use chucks only in the proper manner.  The Three Jaw Self-Center chuck To change the jaws of a three jaw self-centering chuck, proceed as follows: Switch off power to the lathe Clean out any chips from the chuck face and bore. Select the correct size chuck key and fit it to the chuck. Turn the key anti-clockwise to move the jaws outwards Continue turning the key until the scroll frees the jaws. No. 3 jaw should release first followed by No. 2, then No. 1  The Three Jaw Self-Center chuck Clean and replace the jaws back in their storage area Clean the face and jaw slots of the chuck Clean the set of jaws to be fitted Check the serial number to confirm that they are a seat. The same serial number must be stamped on the back of the chuck. This is to ensure concentricity of jaws. Lightly oil the internal scroll of the chuck and the mating teeth of the jaws Do not over oil, as excess oil will be thrown out of the chuck when the spindle is rotated.  The Three Jaw Self-Center chuck Turn the chuck key to rotate the scroll until the start is visible in the jaw slot Select the jaw number 1 and locate it in the slot  The Three Jaw Self-Center chuck Turn the chuck key clockwise to engage the start of the scroll into the first tooth of the jaw. Press the jaw firmly into the slot. Back off the scroll slightly to assist the engagement. When number 1 jaw has engaged into the scroll, continue turning the chuck key to rotate the scroll one third of a turn anti-clockwise. This brings it into position to engaged the next jaw. Select number 2 jaw Enter the jaw into the slot Engage the start of the scroll Turn the scroll to the next position and engage number 3 jaw. When all the jaws have been engaged, turn the chuck key to close the jaws into the centre of the chuck. Check the relative position of each jaw. They should be concentric to the chuck body. Remove the chuck key from the chuck.  The Three Jaw Self-Center chuck NOTE: The three jaws of the chuck must be engaged correctly within the first turn of the scroll. The jaws must also be engaged in the sequence 1, 2, 3 to maintain the self-centering features of the chuck.  The Four jaw Independent Chuck This chuck has four jaws that can be moved independently of each other. The chuck is used to hold the regular and irregular or odd shaped work. Advantages: Each jaw can be moved independently by turning a screw with a chuck key Work can be held very firmly because each jaw opposed the others Work can be set up to run very true by adjusting the jaws and checking the work with a dial indicator Each jaw can be reverse independently to enable odd shaped work to be held Concentric circles marked on the face assist in locating work centrally.  The Four jaw Independent Chuck To reverse the jaws of a four jaw independent chuck proceed as follows: Switch off the power to the lathe Clean down the chuck its bore with a brush Fit the correct chuck key and turn it anti-clockwise Continue turning the key until the jaw disengages from the screw Remove the jaw from the chuck body Remove the chuck key Inspect the thread teeth on the back of the jaw Look for the damaged teeth or embedded cuttings Clean the jaw and slot of the chuck Lightly oil the thread and jaw slot Too much oil will throw out when the lathe spindle is rotated  The Four jaw Independent Chuck Reverse the jaw Enter the jaw into the slot Replace the chuck key and turn it clockwise Engage the start of the thread into the jaw Adjust the jaw inwards until it flush with the outside of the chuck Complete the sequence for the other three jaws The jaws may be fitted in any order. Remove the chuck key from the chuck Never allow the jaws to protect too far out from the outside of the chuck. Do not attempt to hold work unless at least one half of the teeth of each jaw is engaged with the thread. Always turn the chuck one complete turn by hand. This will ensure that all the jaws clear the bed or the cross slide of the lathe when holding large or odd shaped work.  Head Stock Center The headstock spindle is bored out to standard taper to receive the headstock centre. On a lathe that has a large spindle bore a sleeve is required to reduce the size of the taper. The headstock centre is machine to a 60-degree included angle point. This locates in a mating centre hole drilled into the end of thew work. The centre supports and rotates with the work. Because it rotates with the work, the centre must run perfectly true. The centre can be left soft. This enables it to be machined true in position in the headstock. A hardened headstock centre must be checked with a dial indicator to test if it is running true.  Head Stock Center Fit the headstock centre into the spindle as follows: Clean the centre and sleeve thoroughly Check the sleeve and centre for damage or burrs Clean the bore of the headstock spindle Fit the sleeve into the spindle The sleeve should be flush or project slightly from the end of the spindle Fit the centre into the sleeve The centre should project about one and a half times the length of the point from the sleeve. Test the accuracy of the centre by rotating the spindle by hand and checking with a dial indicator. The spindle should be rotated slowly to prevent damaging indicator plunger face.  Head Stock Center If the centre does not run true: Remove and check the inside of the sleeve and spindle for bruises or chips. Clean and reassemble. A hardened centre that cannot be made to run true needs regrinding When fitting centres and sleeves into the headstock do not oil the centre or the sleeve. The oil will prevent the centre from holding in the taper. If centres are to be left in the lathe for any length of time, it is advisable to lightly wipe the holding surface with an oily cloth. This prevents the centre rusting into the taper an making it difficult to remove.  Head Stock Center To true a soft headstock centre proceed as follows: Use a corner of a smooth file to test if the centre is soft enough to machine Hardened centres need to be trued in a grinding machine. Fit the centre into the headstock sleeve Set the compound rest so that the top slide is at 30 degrees to the lathe centre line Start from the centre and take a light cut off the tapered face of the centre. Feed the tool slowly with the top slide to produce a smooth finish. Remove as little metal as possible from the centre, only enough to true the surface. The cutting tool must be accurately set at centre height. Remove the sharp point produced on the centre, with a smooth file  Head Stock Center Removing the Centre Remove the headstock centre and sleeve by knocking it out with a bar placed in the rear end of the headstock spindle. The bar must have a soft end to prevent damage to the centre or sleeve. Support the centre and sleeve when it is being removed. Do not allow it to fall out on to the bed of the lathe. Other Work Holding Accessories  Lathe Carrier Work to be turned between centres is driven by a clamp attached to the end of the work The clamp called a carrier has a leg or tail that locates against the pin of the driving plate fitted to the lathe spindle. Bent trail carriers engage into a slot in the drive plate.  Lathe Carrier Fitting a Carrier to the Work Select the size of carrier in proportion to the work. The carrier should fit clearly over the work. Large heavy carriers used on small diameter slender work may create an out of balance condition. Select either a straight or bent tail carrier to suit the type of driven plate. Locate the carrier so that its full width is supported on the work Use a piece of scrap metal under the clamping screw to protect any finished surface. Tighten the clamping screw firmly. A small flat may need to be filed on the work to locate the screw to give a positive drive. This may be necessary for screw cutting or heavy cutting. Locate the carrier so that the tail engages fully against the pin of the drive plate. When a bent tail carrier is used engaged the tail carrier is used engage the tail in the drive plate slot.  TAILSTOCK CENTER The tailstock centre is held in the tapered bore of the tailstock spindle. It supports the right hand end of work to be turned between centres. 1. PLAIN CENTRES The tailstock centre is similar to the headstock centre except that it must be hardened. The work rotates on the tailstock centre, therefore, the mating surfaces between the centre and the work must be lubricated.  TAILSTOCK CENTER 2. LIVE CENTRES Live centers are tailstock centre that run on roller or ball bearings. This enables the point of the centre to rotate with the work. Excessive pressure on the centre would cause the bearings to overheat and become damaged. Live centres have the following advantages: Lubrication is not needed between the centre and the work The work can be rotated at higher speeds Heavy cutting loads can be carried by the centre 3. PIPE CENTRES Pipe centres are similar to live centres. Cones can be attached to enable the centre to support work that has a large bore. Pipe centres would not normally be run at as high a speed as live centres.  TAILSTOCK CENTER FITTING AND REMOVING A CENTRE To fit a centre to the tailstock proceed as follows: Select a suitable centre to match the standard taper of the tailstock spindle. Use the edge of a smooth file to check that the centre is hardened Inspect the bearing surface of the point The surface must be smooth and clean Damaged centres need to be reground Clean the tapered surface of the centre Remove the protective plug from the bore of the tailstock spindle. Make sure that the bore is clean and free from oil or cuttings. Place the centre about half its length into the bore. Seat the centre firmly into the bore by a final sharp movement. Dirt or chips will prevent the centre from seating correctly into the taper  TAILSTOCK CENTER FITTING AND REMOVING A CENTRE The centre should project at least one and a half times the length of the point from the spindle. Remove the centre from the tailstock as follows: Release the spindle locking clamp Turn the hand wheel of the tailstock anti-clockwise to retract the spindle Retract the spindle until resistance is felt as the end of the threaded spindle contacts the end of the centre Apply slightly greater pressure and continue turning The centre will be released from the taper Be prepared to hold the centre as it is freed from the taper to prevent damage to the centre and lathe bed. Place the centre back in its storage area All tools or equipment held in the tailstock are released in this way.  TAILSTOCK CENTER Some tailstock spindles are bored right through. The operating thread is on the outside of the spindle. Remove the centres or equipment from this type of spindle as follows: Support the centre with the left hand Place a soft-headed knock out bar into the open right-hand end of the spindle Rap the bar firmly against the end of the centre Tapered shank drills, drill chucks, reamers and tap and die holders can be fitted in the tailstock spindle. Some means of preventing the drill from turning in the spindle must be used when large diameter drills are being used in the tailstock. Two common methods of preventing rotation is by fitting either a lath carrier or a drill holder to the drill. This is to guard against damage to the spindle taper surface.  Steady Rest Steady rests are lathe attachments used to support long or slender work. They prevent the work from being bent or deflected by the cutting tool during machining. Two types of steadies are used. They are: The Travelling Steady The Fixed Steady  Steady Rest 1. TRAVELLING STEADY The travelling steady is bolted to the saddle of the lathe and moves along with the cutting tool The steady is sued to prevent long slender work from springing away from the cutting tool while the work is being turned. The steady consists of a frame holding two adjustable bearing pads. The pads are positioned 90 degrees apart. One pad is situated behind the work, directly opposite the cutting tool. The other pad is situated on top of the work. Each pad is adjusted by means of a screw thread and can be locked in the required position.  Steady Rest To set the travelling steady for parallel turning proceed as follows: Clean the locating surfaces of the saddle and the steady Clamp the steady firmly in position Keep the pads clear of the work Set the cutting tool in advance of the steady pads Take a cut at the tailstock end of the work Make the cut long enough to provide a true surface for the pads to operate on.  Steady Rest Adjust the pads to lightly touch the trued surface Lubricate the surface between the work and the pads continually while the cut is taking place Reset the pads for each cut taken. Work that is found to be larger in diameter at its centre (Barrel shape) after being turned with the aid of a travelling steady, indicates that the pads were not adjusted close enough to the work. Pads that are too tightly adjusted against the work will spring the work against the tool. The pads will also wear rapidly.  Steady Rest 2. FIXED Steady The fixed steady is bolted directly on to the top of the lathe bed. It can be positioned anywhere along the bed. The steady is used to support long slender work that is held between centres, or to support one end of long work that has its other end held in a chuck. The steady consists of a frame that has three adjustable bearing pads. Each pas is operated by a screw thread and can be locked in the required position. The frame is hinged to allow the work to be placed in the steady.  Steady Rest Set a fixed steady to support long cylindrical work, that has one end held in a chuck, as follows: Clean the base of the steady and the lathe bed Clamp the steady in position on the bed Set the work up true in the chuck True the other end. Keep the pads well clear  Steady Rest Adjust the two lower pads to just touch the surface of the work Adjust the top pad down to just touch the work surface Lubricate the surface between the work and the pads. The three pads of the steady should be adjusted to just touch the work surface. It should be possible to rotate the work freely in the steady.  Steady Rest If the work is running true and the pads are adjusted correctly the work will be accurately lined up with the axis of the lathe. This is most important. Any pressure applied by the steady rest that moves the end of the work out of line with the axis of the lathe will cause the work to flex. Heavy work that is too rigid to flex will work its way out of the chuck.  Steady Rest Cat Head Irregular shaped or out of round work can be supported in a fixed steady by using a “cat head” The cat head consists of a sleeve which is placed over the workpiece. Four adjusting screws on each ends are used to true the cat head with the axis of the work. The steady rest is then set to the cat head diameter. References Website https://www.google.com/search?q=dividing+head&tbm=isch&ved=2ahUKEwjbvdbZ9_7uAhWOA6YKHZraBRQQ2-cCegQIABAA&oq=dividing+head&gs_lc p=CgNpbWcQAzIECAAQQzIECAAQQzICCAAyAggAMgIIADICCAAyAggAMgIIADICCAAyAggAOgUIABCxAzoHCAAQsQMQQzoICAAQsQMQgwFQ9qTCAVjqv8IB YPDDwgFoAHAAeACAAZUBiAGoCZIBBDExLjKYAQCgAQGqAQtnd3Mtd2l6LWltZ8ABAQ&sclient=img&ei=EWU0YJvxO46HmAWatZegAQ&bih=821&biw=14 40 https://www.google.com/search?q=milling+machine&tbm=isch&ved=2ahUKEwijvozKg__uAhUTAKYKHXxdC2AQ2-cCegQIABAA&oq=milling+machine&gs _lcp=CgNpbWcQAzIHCAAQsQMQQzICCAAyAggAMgIIADICCAAyAggAMgIIADICCAAyAggAMgIIADoECAAQQzoICAAQsQMQgwE6BQgAELEDUPGeJVimuiVg9 sAlaABwAHgAgAGBAYgB7wqSAQQxMi4zmAEAoAEBqgELZ3dzLXdpei1pbWfAAQE&sclient=img&ei=hnE0YKPjIJOAmAX8uq2ABg&bih=821&biw=1440 https://www.google.com/search?q=duplex+manufacturing+type+milling+Machine&tbm=isch&ved=2ahUKEwi5vpLCtvruAhXGBt4KHVJ9D_4Q2-cCegQIAB AA&oq=duplex+manufacturing+type+milling+Machine&gs_lcp=CgNpbWcQA1ClrVpYtLtaYP_IWmgAcAB4AIABUYgByQOSAQE2mAEAoAEBqgELZ3dzLXdpei 1pbWfAAQE&sclient=img&ei=2QcyYPntFsaN-AbS-r3wDw&bih=821&biw=1440#imgrc=kPVWmghKPXLyVM Book: S.FKrar, J.W.OSWALD. J.E. ST Omand,Technology of machine tools, third edition, Gregg Division/McGraw Hill Book Company