LAB 01 LAYOUT OF MACHINE TOOL LAB NAMES OF MACHINE TOOL LAB APPARATUS Center lathe Bench lathe Turret lathe Emco lathe Universal milling machine Tool grinder CNC machine Cylindrical grinder Surface grinding machine Shaper machine Drill press (upright) Pedestal drill press Power hacksaw White board Student chairs
CENTER LATHE MODEL: CL 305 MANUFACTURER: PECO SWING: 305 mm MOTOR CAPACITY: 7.5 HP
It is a basic type of lathe which spins a block of material to perform various operations such as cutting, knurling, drilling, boring, reaming, thread cutting, taper turning etc with tools that are applied to the workpiece to create an object which has symmetry about an axis of rotation.
CONSTRUCTION OF CENTER LATHE It consists of many parts such as headstock, bed, carriage and tailstock and all other accessories which are listed below.
HEAD STOCK The headstock houses the main spindle, speed change mechanism and change gears. The headstock is required to be made as robust as possible due to the cutting forces involved, which can distort a lightly build housing and induce vibrations that will transfer through to the workpiece, reducing the quality of the finished workpiece.
SPINDLE The main spindle is generally hollow to allow long bars to extend through to the work area, this reduces preparation and waste of material. The spindle then runs in precision bearing and is fitted with some means of attaching work holding devices such as chucks.
GEAR BOX The spindle was directly driven by a dedicated electric motor using gear box. The fully geared head allows the speed selection to be done entirely through the gear box.
BED The bed is a robust base that connects to the headstock and permits the carriage and tailstock to be aligned parallel with the axis of spindle. This is facilitated by hardened and ground ways. Types of beds include inverted V beds, flat beds and combination V and flat bed. V and combination beds are used for precision and light duty work while flat beds are used for heavy duty work.
CARRIAGE Carriage holds the tool bit and moves it longitudinally(turning) or perpendicularly(facing) under the control of operator. Carriage can move manually via the hand wheel or automatically by engaging the feed shaft with the carriage feed mechanism. The hand wheels on carriage and its related slides are usually calibrated both for ease of use and to assist in making reproducible cuts.
Parts of carriage are as follows:
1-SADDLE The casting that fits onto the top of bed and slides along it is known as saddle. It moves only longitudinally.
2-CROSS SLIDE It stands a top the saddle of the carriage and has a feed screw that travels perpendicular to the main spindle axis. This permits facing operations to be performed and the depth of cut to be adjusted. This feed screw can be engaged through a gear train to feed shaft to provide automated power feed movement to cross slide.
3-COMPOUND REST It is attached on the top of cross slide and supports the cutting tool. It is graduated so that any angle can be set for taper turning but it is mostly used for short tapers.
4-TOOL POST The cutting tool is mounted in the tool post which is attached to the top of compound rest .
5-APRON The vertical often flate and rectangular plate fastened to the front of the saddle is known as apron and carries a selection of gears and controls that allow the carriage to be power driven up and down the bed and also engage the screw cutting feed and various powered tool feeds should they be fitted.
TAILSTOCK :The tailstock is a tool header directly mounted on the spindle axis opposite to the head stock. It has two main parts Upper part Lower part Upper part motion is very critical. It moves not only longitudinally but also in different directions while lower part of tailstock moves only in longitudinal direction.
TAILSTOCK SPINDLE:It does not rotate but does travel longitudinally under the action of hand wheel.
QUILL Sliding member of tailstock is known as quill which can move outward and inward in which dead center is mounted.
FEED AND LEAD SCREW The feed screw is a long drive shaft that allows a series of gears to drive the carriage mechanisms. These gears are located in apron of carriage. Both the feed screw and lead screw are driven by either the change gears or an intermediate gear box, known as quick change gear box. The lead screw will be manufactured to either imperial or metric standards and will require a conversion ratio to be introduced to create threads forms from a different family.
External operations 1-Turning:It is a process of reducing diameter of work piece to obtain desird shape, size and accuracy by using a turning tool. It may be -Straight turning -Taper turning For taper turning, four methods are used -Compound rest method -Taper turning by a form tool -Taper turning by setting over tail stock -Taper turning attachment. 2-Facing:It is the process of reducing length of work piece to obtain desired size, shape, and accuracy by using a facing tool.
3- Thread cutting:It is a process of making threads on work piece by using a thread cutting tool which moves axially along side of work piece
4- Grooving:It is a process of making grooves in work piece by using a turning tool moves radially into side of work piece cutting a grooves equal in width to cutting tool.
Internal operation:1-Drilling: It is a process of making hole in work piece by using twist drill mounted in tail stock.
2- Boring: It is a process of enlargement of holes by using a boring tool.It is commonly performed after drilling.
3-Reaming: It is a process of giving smoother internal finish to a hole and to obtain a more accurate diameter. It is also performed after drilling.
BENCH LATHE Model:-BL115 Manufacture:-PECO Swing:The name bench lathe implies a version of the class of lathe small enough to be mounted on a work piece but still full featured and larger then mini lathe or micro lathe. Using a bench lathe , different operation, drilling, knurling, cutting etc. can be performed to create a new object.
Part of bench lathe:1-Head Stock:On the left hand side of bench lathe,the head stock is located.A head stock is the section of the lathe that holds spinning bearing.
SPINDLE:-
It is located in head stock.It is the main rotating shaft on which the chuck is mounted .It is supported by precision thrust bearings mounted in the head stock casting and is driven by a toothed pulley and belt which runs down to a smaller toothed pulley on the motor.
BED:A bench lathe has a bed or horizontal beam that supports the main parts of bench lathe and it is also ued to allow the excess material to fall away from the work surface.
CARRIAGE:Bench lathe also has a carriage which holds the tool and moves it longitudinally or perpendicularly to perform the different operations.Parts of Carriage are
1. SADDLE:It fits on the top of the bed and it moves carriage only in the longitudinal direction.
2. CROSS SLIDE:It is mounted on the top of the saddle of carriage and allows the tool to move towards or away from work piece,changing the depth of the cut.
3. COMPOUND REST:It is attached on the top of cross slide and supports the cutting tool.It is graduated to perform the taper turning.
4.TOOL POST:The cutting tool is secured in the tool post which is mounted on the top of the compound rest.
5.APRON:It is the vertical often flat and rectangular plate fastened to front of saddle and it carries a selection of the gears and controls and the clutches that allow the carriage to be power driven up and down the bed and also engage screw cutting feed and various powered tool feeds.
TAIL STOCK:It is rear section of machine that is located to the left of the bed.The purpose of this assembly isto support the other end of the work piece and allow it to rotate.For some turning operations,workpiece is not supported by tail stock so that material can be removed from the end.
LEAD SCREW:-
This is a long threaded rod normally found running along the front of the bed and advances carriage for thread cutting operations.
FEED ROD:It is unthreaded rod below the lead screw and it advances carriage for any operations other than threading when automatic feed lever is engaged.
OPERATIONS PERFORMED BY BENCH LATHE: Turning Boring Facing Drilling Thread cutting Reaming
TURRET LATHE:MODEL:- TL 25 MANUFACTURER:- BECO It is a form of metal working lathe that is used for repetitive production of duplicate parts which by nature of their cutting process of are usually interchangeable.It evolved from the earlier lathes with the addition of the turret which is indexable tool holder that allows multiple cutting operationsto be performed ,each with a different cutting tool in easy and rapid succession.
PARTS OF TURRET LATHE:HEAD STOCK:It is located on the left side of the lathe.Head Stock houses the main spindle,speed change mechanism and change gears.In Head Stock of turret lathe,rapid shifting is done between at least two spindle speeds with a brake to stop the spindle very rapidly and automatic feeding out and clamping the bar stock which passes through spindle.
TURRET HEAD:-
In this type of lathe ,tail stock is replaced by turret head. Hexagonal turret head has six faces .Each face has one tool.The hexagonal turret can be indexed about its vertical axis,to bring each of its faces into the working position.The turret alongwith the saddle can be moved longitudinally either by a manual feed or a power feed.
STAR WHEEL:At the end of the turret working travel towards the spindle,the turret is moved back with the help of the star wheel.During this motion,it automatically indexes at end of movement thus bringing each of the six faces into working positions.
SQUARE CROSS SLIDE:In turret lathe,tool post is replaced by the square cross slide which can hold four tools.The movement of the tools on the cross slide is perpendicular to the lathe axis.
REAR CROSS SLIDE:In turret lathe,there is aspecail arrangement of Rear Cross Slide.Two more tools can be held in the rear cross slide.The tools in the rear cross slide areused to cut grooves,to face end or shoulders and to cut of the the work piece.There is no compound rest,tail stock and tool post in turret lathe.
OPERATIONS PERFORMED BY THE TURRET LATHE:A Turret can perfrom the following functions Cutting Facing Thread cutting Grooving Drilling Boring Tapping As turret lathes can perform operations with a whole set of cutting tools installed in a definite sequence on the turret and on the cross slide.Therefore turret lathes have higher production capacity than the centre lathes and are used in lot production.
EMCO LATHE:MODEL:- EMCO MAXIMAT V10 P The Emco Maximat V13 was a very well made all geared head lathe that was supplied with a hardened bed as standard.It was probably the largest conventional centre lathe made by EMCO Company.
PARTS OF EMCO LATHE:BED:It provides foundation for whole machine and holds head stock ,tail stock and carriage in alignment.
HEAD STOCK:The head stock is normally mounted rigidly to bed and holds all mechanisms including the various kinds and combinations of pulleys or gears so that the spindle can be made to turn at different speeds. Carriage:-
1. SADDLE:It is a casting that fits onto the top of the bed and slides along it.It moves longitudinally
2. CROSS SLIDE:It is mounted on the top of saddle and it moves across the workpiece so that facing operation to be performed and depth of cut can be adjusted.
3. COMPOUND REST:It is mounted on top of cross slide.It is usually graduated and used for taper turning.
4.TOOL POST:Tool is secured in the tool post to perform the different operations.It is mounted on the top of the compound rest.
5.APRON:It is vertical often flat and rectangular plate fastened to front of saddle and carries a selection of the gears and controls that allows the carriage to be power driven up and own the bed
TAIL STOCK:It is mounted on the right side of Emco lathe. Its arranged to slide along the bed and can be locked to any convenient point the upper part can be moved in and out. Its sliding member is known as quill in which dead centre is mounted.
LEAD SCREW:It is long threaded rod which advances carriage for thread cutting operations.
FEED RATES:It is unthreaded rod below lead screw that advances carriage for operations other than the thread cutting. OPERATION PERFORMED BY EMCO LATHE: Facing Turning Grooving Boring Drilling Thread Cutting
UNIVERSAL MILLING MACHINE:Model Manufacturing:-
Pak-Oerlikon
A Milling machine is a machine tool for the shaping of metal and other solid materials. In milling machine, work piece also moves against the rotating cutter. PARTS OF MILLING MACHINE:Head Drive:It is that part of drive system that transforms electrical power from a motor to mechanical power in spindle. The drive system also provides machinist to change the speed of spindle and therefore the cutting tool. Column:-
Sitting on base is the column whose main function is to hold the turret. The turret allows milling head to be rotated around column’s centre. Ram:The over-arm (Ram) slides on turret and allows the milling head to be repositioned over the table. Quill:The quill moves vertically in head and contains spindle in which cutting tools are installed. Quill feed hand drill:It moves the quill up and down within the head as does the quill feed lever. Knee:The knees move up and down by sliding on ways that are parallel to column. Saddle:The saddle sits on knee and allows translation of work table. Longitudinal Transverse Hand Wheel:It moves the worktable to the left and right.
Cross Traverse Hand Table:It moves the work table in and out. Vertical Movement Crank:It moves the knee, saddle and work piece up and down.
TOOL GRINDER:It is a measure tool used for grinding which is a type of machining using an abrasive wheel as cutting tool. Each grain of abrasive on the wheel ‘s surface cuts a small chip from the work piece via shear deformation. Mechanism:-
It removes material from the work piece by abrasion which can generate substantial amount of heat so they incorporate a coolant to cool the work piece so that it does not overheat and go outside its tolerance. SURFACE GRINDING MACHINE:Manufacture:-
Jones Shipment
A surface grinder is a machine tool used to provide precision ground surfaces either to a critical size or for the surface finish. PARTS OF SURFACE GRINDING MACHINE:Table:The machine consists of a table that traverses both longitudinally and across the face of the wheel. Hydraulics:The longitudinal feed is usually powered by hydraulics as may the cross feed. Grinding wheel:The grinding wheel rotates in the spindle head and is also adjustable for height. Chuck:Depending on the material, the work is generally held by the use of a magnetic chuck. This may be either an electromagnetic chuck, or a manually operated permanent magnetic chuck.
Materials Used For Surface Of Grinding wheel:Aluminium oxide, silicon carbide, diamond and cubic boron nitride are four commonly used abrasive materials for surface of grinding wheels of these materials, aluminium oxide is most common. Cooloant:The machine has provision for the application of coolant as well as the extraction of metal dust. CYLINDRICAL GRINDERS:Manufacturer:-
Jones Shipment
Cylindrical grinders are a class of grinding machines on a work piece that are symmetrical about an axis of rotation. (e.g. cylindrical) PARTS OF CYLINDRICAL GRINDER:Grinding Wheel:It is used as a cutting tool. In this grinder, wheel is held at a slight angle to the part so that there is a force feeding the part through the grinder is particularly efficient. Work blade:In this machine grinding wheel rests on work table. “In grinder both work piece and tool move and this grinder can also be used as internal grinder” Coolant:This machine has provision for the application of the coolant to minimize the heat produced during grinding process.
SHAPER MACHINE:Model:-
SH-460
Manufacturer:-
Peco
A shaper is a machine tool used for shaping or surfacing metal and other material. PARTS OF SHAPER MACHIINE:Table:The work piece mounts on a grid, box shaped table in front of machine. The height of table can be adjusted to suit this work piece and the table can traverse side ways underneath the reciprocating which is mounted on ram. Ram:The ram slides back and forth above the work at the front end of the ram is a vertical tool slide that may be adjusted to either side of the vertical plane. Tool slide:-
The tool slide holds tool post from where the tool can be positioned to cut the straight, flat surface on top of work piece. Cutting Fluid:It may be employed to increase the finish and prolong the tool’s life. Rotary Table: Vertical shapers are generally fitted with rotary table to enable curved surface to be machined. Tool Feed Handle:It can be turned to slowly feed the cutting tool into material as ram moves forwards and backwards. Vice:It holds the material securely. It rests on steel table which can be adjusted so that it can be moved up and down and then locked in position. Clutch Handle:Pulling back on clutch handle starts the ram movimg forward or backward
UPRIGHT DRLL PRESS:Model:-
UD-50
The drill press is one of the most frequently used machine tools. They are used mainly for drilling holed but reaming, boring can also be accomplished with drill press.
PEDESTAL DRILL PRESS:Model:-
PD-20
This drill press is used to drill holes in wood, plastic, aluminium, brass. Steel and most other common engineering materials. PARTS OF DRILL PRESS:Drill Chuck:It is apart of drill press which is used to hold cutting tool such as twist drill, tap wrench, reamer etc. Spindle:Spindle rotates the cutting tool which is clamped in drill chuck, after the work piece is secured in vise, it must be aligned under the spindle to perform desired operation on a particular place. Feed Lever:It is used to raise and lower the spindle. The drill press allows operator to hand feed or power feed the tool into work piece. Vise:_ Vise is used to hold work piece. In drill press cutting tool is rotated while work piece remains stationary. Table:It is used to support work piece and also to clamp the parts being machined with drill press. It may be moving or stationay.
THE CONTROLS:Power/Range:This switch has 3 positions, high range, low range, and off. Low range is used when larger holes or harder materials need to be machined while high range is useful when small and softer material are being drilled. Spindle Speed:-
Both high range and low range spindle speeds are changed using this control. The speed should only be changed while motor is running. POWER HACKSAW:It is a type of hacksaw that is provided power either by an electric motor or connected to a stationary engine. When circular material is cut hacksaw is used. Blades of Hacksaw:The hacksaw has blade which has reciprocating motions. The fixed material on the hacksaw is cutoff as a result of blades action. Procedure of cutting circular material:The power hacksaw is easy to use. Firstly material is fixed in the vise of hacksaw at desired length. A switch of hacksaw turns on and lowers blade slowly on to the material. When material is finished cutting, the hacksaw stops automatically. CNC MACHINE:They are modern machine and are in place of older production machines due to their ease of setting and operation. In this machine tools paths are programmed CAD/CAM processes, and then program is uploaded to machine. Machine’s output is totally dependent on the developed program because once the machine is set according to program, it works accordingly to program. This machine is safe to operator and is easy to use.
Experiment No. 2 OBJECTIVE: Alignment test of lathe machine (BL-115). Apparatus: Dial gauge Magnetic stand Testing mandrel Steel rule Chuck key Dead centre Tests to be performed:1. Check straightness of bed. 2. Check taper hole in spindle. 3. Check bed level of cross direction. 4. Spindle axis parallel with bed. 5. Tolerance of centers. Procedure:In order to check alignment of lathe machine, we have performed the above mentioned tests as follows. Straightness of bed:
Place the dial gauge attached with magnetic stand on cross slide.
Set the dial gauge in such a way that its tip touches the bed of lathe.
Move the saddle in forward direction up to a particular length of bed say 300mm.
Dial gauge shows different readings during this forward motion.
Noted the readings of the dial gauge which is actually the deviation in straightness of bed.
Taper hole in spindle:
To check taper hole in spindle mount the tapered mandrel in tapered spindle (quill) of tail stock.
Set the dial gauge in such a way that its tip touches the surface of mandrel.
Move the saddle in forward direction above which dial gauge attached with magnetic stand is placed throughout the length of spindle.
Dial gauge show readings during this motion.
Then noted the reading of dial gauge which is actually the deviation in tapered hole of spindle. Bed level of cross direction:
Placed the dial gauge attached with magnetic stand on cross slide.
Set the dial gauge in such a way that its tip touches the surface of bed.
Moved the cross slide across the bed and noted the value of dial gauge.
The reading of dial gauge is actually the deviation in bed level of cross direction.
Spindle axis parallel with bed:
Mounted the mandrel in spindle of head stock.
Placed the dial gauge attached with magnetic stand on cross slide in such a way that its tip touches the surface of mandrel.
Move the saddle towards head stock.
The dial gauge show different readings.
Then noted the reading of dial gauge which is deviation in spindle axis parallel with bed.
Also find circular deviation of spindle.
Tolerance of centers:
Mounted live centre in headstock and dead centre.
Fix the testing mandrel between live and dead centre.
Placed the dial gauge attached with magnetic stand on cross slide so that its tip touches the mandrel surface.
Move the saddle in such a way that tip of dial gauge remains in contact throughout the length of mandrel.
Noted the reading of dial gauge which is actually the deviation in tolerance of centers.
Comments:Alignment test of any machine is very important in order to improve the accuracy of machine. Because if there is some error in alignment of machine, any product manufactured by it will not be accurate. So it is very important to perform alignment tests.
Test No
1)
Alignment test to be performed
Theoretical deviation
Practical deviation
Straightness of bed
0.02mm/300m m
0.014mm/300 mm
Error Positive
Negativ e
----
-0.14mm
2)
Taper hole in spindle
3)
Bed level of cross direction
0.005mm/300 mm
0.02mm/300m m 4)
0.29mm/195 mm
Spindle axis parallel with bed
Circular Tolerance of centers
0.01mm/300m m
0.12mm/270 mm
----
0.2mm/30mm
0.01mm/1000 mm
0.48mm/450 mm
OBSERVATIONS : TEST NAME
DISTANCE MOVED
----
----
-0.08mm
0.12mm
----
----
-0.2mm
0.48mm
----
0.08mm/120 mm
Longitudinal 5)
+0.29m m
ERROR
EXPERIMENT NO :- 3 OBJECTIVE:Alignment test of drilling machine (UD - 50)
Apparatus:• • • • •
Dial gauge. Magnetic stand. Testing mandrel. Spirit level. Steel rule.
Test to be Performed:Test No: 1 To check straightness of spindle.
Test No: 2 To check taper hole in spindle.
Test No: 3 To check straightness of the vertical column.
Test No: 4 To check the working table.
Procedure:-
In order to check the alignment of drilling machine, we have performed the above mentioned tests as follows:
1) To check straightness of spindle :• • • •
Setup the magnetic stand on vertical column of drill. Adjust the dial gauge in it, in such a way that the dial gauge knob touches vertical spindle. Now move the spindle upward / downward using the hand wheel such that dial gauge knob slides over it. Note the maximum value of deflection of the dial gauge needle in either direction to check the straightness of spindle.
2) To check taper hole in spindle:• • • •
First of all, fix the testing mandrel in the vertical spindle taper hole. Next setup the magnetic stand along with the dial gauge on the vertical column in such a way that dial gauge knob just touches the mandrel’s surface. Adjust the needle zero position of the dial gauge. Now to check the taper hole in the vertical spindle of the drill, move the spindle upward / downward through 300 mm with the help of hand wheel in such a way that the knob of dial gauge slides over the mandrels surface and while doing. So note down the maximum value of gauge deflection.
3) To check the straightness of vertical column:-
•
•
First of all, fix the magnetic stand on working table of drill and set the magnetic stand on working table of drill and set the dial gauge in it such that the knob of dial gauge touches the vertical column of drill and adjust the needle to zero position. Now with the help of a hand wheel (provided at lower side of drill) move the table upward , over a distance of 300 mm. While doing so, note down the maximum dial gauge value either direction for present value of the test.
4) To check the working table :In order to check the straightness of working table just place the spirit level on working table of drill and see whether it’s bubble is in it’s center or not.
OBSERVATIONS : TEST NAME
1. Straightness of spindle Linear Circular
2. Taper hole in spindle Linear circular
3. Straightness of vertical column 4. Straightness of working table
DISTANCE MOVED
ERROR Positive
Negative
100 mm
0
-0.02
Dia 470 mm
0.01
-0.04
100 mm
0.015
0
Dia 34.5 mm
0.14
-0.05
0
-0.04
300 mm
0.1 m at 1 m from right to left
EXPERIMENT NO. 4 OBJECTIVE:Manufacture a work piece on lathe machine according to given dimensions. Apparatus:• • • • • •
Lathe machine Raw material for work piece Facing tool Turning tool Threading tool Abrasive finishing paper
Theory:Lathe Machine:The lathe is the forerunner of all machine tools. The first application of the lathe principle was probably the potter’s wheel. This machine rotated a mass of clay and enabled the clay to be formed into a cylindrical shape. The modern lathe operates on same basic principle. The work is held and rotated on its axis while the cutting tool is advanced along the lines of a desired cut. The lathe is one of the most versatile machine tools used in industry. With suitable attachments, the lathe may be used for turning, taper turning, screw cutting, facing, drilling, boring etc. by using cutting tools. The cutting tool may be fed either parallel
or at right angles to axis of work. Cutting tool may also be fed at an angle to axis of
work for machining tapers.
Cutting Speed: Lathe work cutting speed (CS) may be defined as the rate at which a point on the work circumference travels past the cutting tool. It is usually expressed in feet per minute (ft/min) or in meters per minute (m/min). Cutting speed depends on the type of material being cut. If cutting speed is too high, the cutting tool edge breaks rapidly. With too slow cutting speed, time will be lost for machining operation.
Inch Calculations: Cutting speed = ∏ DN/12 where N= No. of revolutions per minute of spindle D = Diameter of workpiece to be turned
Metric Calculations: Cutting speed = DN/320
Lathe Feed: The feed of a lathe may be defined as distance the cutting tool advances along the length of the work for every revolution of spindle. For general purpose machining, 0.010 to 0.015 in (0.25-0.4mm) feed for roughing and 0.003 to 0.005 in (0.070.012mm) feed for finishing is recommended.
Tool Geometry:Lathe Cutting Tools: Most commonly used lathe cutting tools are as follows:
1. Facing tool: Facing is a process of reducing length of workpiece to obtain desired size, shape and accuracy. The tool used for facing is known as facing tool.
2. Turning tool: Turning is a process of reducing diameter of workpiece to obtain desired size, shape and accuracy. The tool used for turning is known as turning tool.
3. Threading tool: Threading is a process of making threads on workpiece. The tool used for threading is known as threading tool.
4. Boring tool: Boring is a process of enlargement of hole after drilling. The tool used for boring is known as boring tool.
5. Parting tool: Parting is a process of separating workpiece from rest of raw material or any other component. The tool used for parting is known as parting tool.
6. Finishing tool: Finishing is a process of making the surface of workpiece smooth. It can be performed by using abrasive paper or finishing tool.
Grooving, undercutting
Facing
or parting
Threading 60
Finishing
Threading ACME Cutting tool geometry also includes proper clearance and rake angles ground on tool bit.
a) Side cutting edge angle: It is angle the cutting edge forms with side of tool shank. It varies from 10° - 20° .
b) End cutting edge angle:
It is the angle formed by the end cutting edge and a line at right angles to the centerline of tool bit. This angle varies from 5° – 15° for roughing cut and from 15° – 30° for general purpose turning tools.
c) Side clearance angle: It is an angle ground on flank of tool below cutting edge. It is generally 6° – 10°.
d) End clearance angle: It is the angle ground below the nose of tool bit, which permits cutting tool to be fed into work. It is generally 10° – 15°.
e) Side rake angle: It is an angle at which face is ground away from cutting edge. It is generally 14°.
f) Back rake angle: It is the backward slope of tool face away from the nose. This angle is generally 20°.
g) Angle of keenness: It is the included angle produced by grinding side rake and side clearance on tool bit. This angle is generally 90° for harder materials.
Lathe operations performed on workpiece:1. Facing: It is a process of reducing the length of workpiece to obtain desired size, shape and accuracy. It is usually done by a facing tool. Workpieces to be machined are generally cut a little longer than required and then end-faced to the proper length. By facing operation, the ends of a workpiece are to be machined square with its axis.
2. Turning: It is a process of reducing the diameter of workpiece to obtain desired size, shape and accuracy. It is usually performed by a turning tool. By using turning process, diameters of different parts of workpiece are to be maintained.
3. Step turning: It is a process to make different steps having different diameters such as in workpiece different diameters 14.4mm, 20.3mm, and 23.5mm are obtained by step turning.
4. Threading: It is a process of making threads on workpiece, by using threading tool. Thread cutting on lathe is a process that produces a helical ridge of uniform section on a workpiece. This is performed by taking successive cuts with a threading tool bit of same shape as the thread form required. We have to make threads of 11 T.P.I. on workpiece up to a length of 55.5mm.
5. Finishing: It is a process to make the surface of workpiece smooth. It is very important and it is usually performed at the completion of other lathe operations. It is usually performed by using abrasive paper, filing or finishing tool.
Procedure to make required workpiece on lathe:1. Cut a piece of material from which the workpiece has to be made slightly longer than the required length by using hacksaw. 2. Mounted the workpiece in chuck of lathe and firstly performed facing operation to reduce the length of workpiece up to required length and to make end face smooth. 3. Performed the turning operation up to the length of 55.5mm by using turning tool, to attain the required diameter of 14.4mm. 4. Performed the step turning to attain the diameters of 20.3mm and 23.5mm up to the lengths of 16mm and 60.5mm respectively. 5. Perform same procedure of step turning on the other side of workpiece. 6. Perform the threading operation on both sides of workpiece to make threads of 11 T.P.I. up to the length of 55.5mm.
7. At the end finishing process has to be performed to make the surface of workpiece smooth.
WORKPIECE MANUFACTURED ON LATHE (All units in mm)
Standard pitch table:- (From 3mm to 12mm)
Nominal diameter (mm)
Thread Pitch (mm)
3 4 5 6 7 8 10 12
0.5 0.7 0.8 1 1 1.25 1.5 1.75
Standard threads T.P.I.:- (From ⅛″-½″)
Nominal size
T.P.I
⅛″ ¼″ ⅜″ ½″
27 18 18 14
Formula to find drill size when performing internal threading through taps: The tap drill size for any American, National or unified thread can be found easily by applying this simple formula.
TDS= D- 1/N where
TDS = tap drill size D = major diameter of tap N = number of threads per inch
EXPERIMENT NO. 5 OBJECTIVE:CNC programming and metal cutting Introduction:The Boxford 160 TCL is British made training computer lathe featuring ISO format machine tool programming. It is a integrated bench top turning system system specifically designed for educational and training installations. It can cut sreel,brass, wood, aluminium, and plastics.It is ideally suited for classroom yet is capable of cutting steel to close tolerances, special accessories also allow the machining of wood and plastics. The lathe has a programming length built in touch sensitive control panel with programming and variable speed of spindle from 40 to 3200 rpm. It an error is made in the block of CNC code. The result is displayed on computer screen and is easily removed on computer.
BOXFORD 160 TRAINING COMPUTER LATHE (TCL)
Capacity and limits 1) Spindle speed range Range # 1
320-----------3200 rpm
Range # 2
160-----------1600 rpm
Range # 3
80-------------800 rpm
Range # 4
40-------------400 rpm
Range # 1 gives maximum speed and Range # 4 maximum torque.
2) Feed rate (G01) Feed rate 10mm/min---500mm/min
3) Rapid transverse (G00) Rapid transverse : 1200mm/min 4) 5) 6) 7)
x axis travels traveling :z axis traveling :- 125mm spindle bore :20mm Main motor :44 KW
75mm(max)
8) Unit selection:1) Imperial dimension format (G70) XX.XXX 12.345
Metric dimension format (G71) Metric dimension is expressed as XXX.XX 123.45
Programming Coordinates:Absolute dimensions:- (G90) In this system,, all programming coordinates are located from a fixed zero absolute point. This dimension is generally used for 2 axis machine.
Incremental dimensions :- (G91) In an incremental numerical control programming each coordinate location is given in terms of distance from previous position of tool. This dimension is generally used for 3 axis machine.
Description of line number used in programming sheet:Line # 10 :- select absolute or incremental dimension (G90 or 91) Line # 20:- unit selection (imperial or metric) Line #30 ;- tool park position (x and z axis) Line # 40 :- spindle start (reverse or forward)
Preparatory codes:- (G codes) These codes are used to change the machining process performed in CNC. Some commonly used G codes are as follows.
Codes
Function
G00
Rapid transverse movement
G01
Linear interpolation
G02
Circular interpolation
G03
Circular interpolation (counter clockwise)
G04
Time Duell
G70
Imperial dimensions
G71
Metric dimensions
G81
Outer dia turning cycle
G82
Facing or grooving
G90
Absolute dimensioning
G91
Incremental dimensioning
G94
Feed per minute
G95
Feed per revolution
G96
Constant surface speed
G97
Constant RPM
Miscellaneous codes:- (M codes) These codes are generally used to change the behavior of machine. Some commonly used M codes are as follows.
Codes
Function
M02
Measure end of program for the single quantity
M03
Start spindle forward
M04
Start spindle reverse
M05
Start spindle
M06
Tool change
M30
Mark the end of program for repeat quantity
M39
Closing automatic chuck
M40
Opening automatic chuck
M81
Output ON/OFF
M97
Continuous manufacture
M99
Continuous code
Program:In catalogue 9
Enter bar information: Outer Diameter: 50mm Internal Diameter (in case of pipe) : 0mm Length : 100mm
Material:
1→ For mild steel or similar 2→ For Brass, Aluminium or similar 3→ For plastics, wax
Programming sheet: Line N10 N20 N30 N40 N50 N60 N70 N80 N90 N100 N110 N120 N130 N140 N150 N160 N170 N180 N190 N200 N210 N220 N230 N240 N250 N260 N270
G 90 71
M
X
Z
I
K
55
5
1
6
50 47
0
F
04
S
2000
01
-70
10
48 0 44 01
-70
10
45 0 40 01
-70
10
42 81
20 37
01
40
01
34 40
01
30 40
0 -30 -30 -45 -30
20
10
10
-45 -30
10
-45
10
N280 N290 N300 N310 N320 N330 N340 N350 N360 N370 N380 N390 N400 N410 N420
-30 01
27 40
01
24 40
01
20 40
01
20 -4
where
L→ Line No. G,M→ Codes X,Z→ Axis I→ Tool number K→ Turret number F→ Feed rate S→ Spindle speed
-45 -30
10
-45 -30
10
-45 -2
10
10 0
21 02
WORKPIECE MANUFACTURED ON 160 TCL (All units in mm)
Experiment No. 6 Study of Universal Milling machine and Gear cutting Milling machines are machine tools used to produce one or more machined surfaces accurately on a piece of material, the work piece, this is done by one or more rotatery milling cutters having single or multiple cutting edges.
Universal milling machine: It is a versatile machine tool that can handle a variety of operations normally performed by other machine tools. It is used not only for the milling of flat and irregular shaped surfaces but also for gear and thread cutting, drilling, boring, reaming and slotting operations.
Parts of universal milling machine: 1) Base: The base gives the support and strength to the machine and act as a reservoir for cutting fluid. 2) Column: The column is the main supporting frame. It is a heavy box like structure. Inside the column, there is space for motor and driving mechanism. The face of the column is a very accurate slide 3) Knee:
The knee is attached to the column face and may be vertically moved on the column face either manually or accurately or automatically. It houses the feed mechanism. 4) Saddle: The saddle is fitted on top of knee and may be moved in or out either manually by means of the cross feed hand wheel or automatically by crosses feed engaging lever. 5) Table: The table rests on guide ways in saddle and travels longitudinally in a horizontal plane. It supports the work. 6) Spindle: The spindle provides the drive for arbors, cutters and attachments used on a milling machine. 7) Over arm: The over arm provides for correct alignment and support of arbor and provide attachments. I t can be adjusted and locked in various positions, depending on the length of arbor and position of cutter. 8) Arbor support: The arbor support is fitted to over arm and can be clamped at any location on over arm. Its purpose is to align and support various arbors and attachments. 9) Arbor:
It is a tapered portion and end of arbor is free, so it can fluctuate. 10) Elevating Screw: It is controlled manually or automatically. It gives upward and downward movements to knee and table.
Indexing It is a process of maintaining same distance or gap between grooves. It can be performed by holding the work piece and rotating it the exact amount for each groove or slot to be cut.
Methods of Indexing 1) Direct Indexing: In direct indexing, the index plate is directly mounted on the dividing head spindle. The intermediate use of worm and worm wheel is avoided. For indexing, the index pin is pulled out on a hole, the work and the index plate are rotated the desired number of holes and the pin is engaged. Direct indexing is the most rapid method of indexing but fractions of a complete turn of spindle are limited to those available with the index plate. 2) Simple Indexing:
In simple or plain indexing, an index plate selected for the particular application is fitted on worm shaft and locked through a locking pin. To index the work through any required angle, the index crank pin is withdrawn from a hole in index plate. This spindle and hence work is indexed through the required angle by turning the index crank through a calculated number of whole revolutions and holes on one of hole circles after which index pin is relocated in required hole. To calculate the indexing or number of turns of crank for most divisions, it is necessary only to divide 40 by number of divisions (N) to be cut or Indexing=40/N Where N = No. of teethes to be cut The usual ratio is 40 turns of index crank to 1 turn of spindle, in other words a ratio of 40 to 1. Now since the index crank make 40 revolutions to 1 of the spindle, one revolution of crank would cause spindle to rotate 1/40 revolution. 3) Compound Indexing: When none of the index plates has a hole circle which would enable the work to be divided by simple indexing method, more involved methods are employed. One method is compound indexing. The compound indexing is achieved in two stages, by using two different hole circles of one index plate. By a movement of the crank in the usual way as in simple indexing, say n1
holes in hole circle N1, with the lock pin engaged in circle N2 of index plate.
By adding or subtracting a further movement by rotating the crank and the
index plate together forward or backward through n2 spaces in the N2 circle by disengaging the locking pin of index plate so that it is free to turn. 4) Angular Indexing: When the angular distance between divisions is given instead of the number of divisions, the setup for simple indexing may be used, however the method of calculating the indexing is changed. One complete turn of index crank turns the work one fortieth of a turn or one fortieth of 360° which equals to 9°. When angular dimension is given in degrees then, Indexing in Degrees = No. of degrees required / 9
If dimensions are given in degree and minutes, then Indexing in Minutes = No. of minutes required / 540 5) Differential Indexing: When it is impossible to calculate the required indexing by simple indexing method, that is when fraction 40/N cannot be reduced to a factor of one available hole circles, then differential indexing is used. With this method, the index plate must revolve either forward or backward a part of turn while index crank is turned to attain proper spacing or indexing. In differential indexing, the index crank rotates dividing head spindle, spindle rotates index plate
after locking pin has been disengaged by means of change gears connecting the dividing head spindle and worm shaft. The rotation of plate may be in same direction (positive) or in opposite direction (negative) of index crank. This change of rotation is affected by an idler gear or gears in gear train. When it is necessary to calculate the indexing for a required number of divisions by differential method, a number is chose close to required divisions that can be indexed by simple indexing.
Index plate: Dividing needs are usually furnished with a set of three index plates having six concentric holes with different number of equally spaced hole side. A typical set has following number of holes. Plate # 1: 15, 16, 17,18,19,20 Plate # 2: 21, 23, 27,29,31,33 Plate # 3: 37, 39, 41,43,47,49
Gears: Gears are used to transmit power from one shaft to other by engaging teeth. Gear terminologies:
Knowledge of more common gear terms is desired to understand gearing and to make calculations necessary to cut a gear.
Circular pitch: It is distance of one point on one tooth to the corresponding point on next tooth. Circular pitch=length of arc ABC =circumference of pitch circle / number of teeth Or with symbols C.P=3.1416*D / N
...... (i)
Where C.P=circular pitch D=Diameter of pitch circle N=Number of teeth From (1) N=3.1416*D / C.P
......(ii)
D=CP*N / 3.1416
......(iii)
Diameteral pitch: It is the ratio of number of teeth for each inch of pitch diameter of the gear. Diameter pitch=number of teeth/pitch of circle diameter D.P=N / D
.....(i)
From (i) following relations are obtained N=D.P*D D=N/D.P
Relation Between circular & diametral pitch: Diametral pitch=3.1416/diametral pitch
.....(i)
Sometimes it is convenient to change circular to diametral pitch or vice versa. So Circular pitch=3.1416/diametral pitch
Addendum:
.....(ii)
It is radial distance between the pitch circle and outside diameter or height of the tooth above the pitch circle In general Addendum = 1 / diametral pitch
Deddendum: It is the radial distance from the pitch of the circle to the bottom of tooth space. Deddendum is equal to addendum. Accordingly, deddendum is found in same way as an addendum that is, Deddendum = 1 \ Diametral Pitch
Working Depth: The sum of addendum and deddendum is called the working depth. It is the actual theoretical length of the tooth.
Clearance:
It is the radial distance between the top of one tooth and the bottom of mating tooth space. Gear must be so proportioned that when a tooth is in mesh with the groove or space between it and adjacent tooth, the top of the tooth will not touch the bottom of the groove, the reason for this, it is impossible to machine the teeth to the exact dimension and accordingly there must be a margin of space to allow for any slight errors and this margin is called the clearance. Clearance = .157 \ DP
Face and Flanks: By definition the face of tooth is that part of the tooth curve which lies between the addendum and the pitch circle. The flank of a tooth is that part of the tooth curve that lies between the pitch circle and the deddendum circle.
Circular thickness It is the tooth thickness measured on the pitch circle. It is also known as the Arc Thickness.
Module :*( Metric gears)
It is the pitch diameter of the gear divided by the no. of teeth. It is an actual dimension.
Pitch Circle: It is a circle that has the radius of half the pitch diameter with its center at the axis of the gear.
Pressure Angle: It is an angle formed by line through the point of contact of two mating teeth and the tangent to the two base circles and a line at right angles to center line of gear.
Root Circle: It is the circle formed by the bottom of tooth spaces.
Whole Depth: It is full depth of tooth or the distance equal to addendum deddendum.
Cutting Spur Gears: Eight cutters for each pitch are as follows,
No. 8 cutter will cut gear from 135 teeth to a rack.
No.7 will cut gear from 55 to 135 teeth.
No.6 will cut gear from 35 to 54 teeth. No.5 will cut gear from 26 to 34 teeth. No.4 will cut gear from 21 to 25 teeth. No.3 will cut gear from 17 to 20 teeth. No.2 will cut gear from 14 to 16 teeth. No.1 will cut gear from 12 to 13 teeth.
Procedure: Mounted the milling cutter on the milling machine arbor. Make sure that the cutter teeth point is in the direction of arbor rotation. Mounted the work-piece in milling machine. Switch on the milling machine and run the work under the cutter. Set the index plate such that the crank pin is inserted in any one hole of 49 hole circle. Raise the table until the cutter just touches the top of work-piece. Now set the automatic feed according to the depth of tooth. After cutting 1st tooth,
move the work-piece back, loose the knee clamp, set the crank pin in 35 holes out of 49 hole circle.
Again placed work-piece under cutter after tightening the clamp. Cut the 2nd tooth to its whole depth.
Repeat this procedure till the completion of total teeth (560. Now remove the work-piece and cutter from machine.
Circular pitch
whole depth
Top
Dedendum
Working depth
Thickness
Pitch diameter
addendum
Face
clearance
Flank Module Outside diameter
outside circle
Root circle
Dimensions of Gear to Be Cut: Outer Diameter of Gear = 87.8 mm No. of Teeth = 56
Whole Depth = 3.27 mm Module = 1.51 But Module Used = 1.5 Index Plate = 17, 19, 21,24,29,33,39,43,49 So, by using simple indexing,
40\n = 40\56 = 5\7 = 5*3\7*3 = 15\21 i.e. 15 holes out of 21 hole circle Or 5*7\7*7 = 35\49 i.e. 35 holes out of 49 hole circle.