Lathe Machine

Introduction

If you are new to metalworking lathes and lathe work, this page will help you understand some of the basic concepts, terminology and capabilities. In essence, a lathe, whether for woodworking or metalworking, rotates a cylindrical work piece along its axis and removes material from the work piece to form it into a specific shape.

On a woodworking lathe, the cutting tools are usually hand-held against a support and are moved in and out and back and forth along the surface of the work by hand to form a shape such as a table leg.

On metalworking lathes, the cutting tools are held rigidly in a tool holder that is mounted on a movable platform called the carriage. The tool is moved in and out by means of hand cranks and back and forth either by hand cranking or under power from the lathe. The result is that material can be removed from the work piece under very precise control to produce shapes that are truly precision made. Dimensional accuracies of one-one-thousandth of an inch (.001") are typical. However, because of the inherent rotational nature of a lathe, the vast majority of the work produced on it is basically cylindrical in form. In spite of this, the lathe is an extremely versatile machine capable of producing a surprising variety of objects.

 

 

 

 

 

History

The lathe is an ancient tool, dating at least to the Egyptians and known and used in Assyria, Greece, the Roman and Byzantine Empires.

The origin of turning dates to around 1300 BC when the Egyptians first developed a two-person lathe. One person would turn the wood work piece with a rope while the other used a sharp tool to cut shapes in the wood. The Romans improved the Egyptian design with the addition of a turning bow. Early bow lathes were also developed and used in Germany, France and Britain. In the Middle Ages a pedal replaced hand-operated turning, freeing both the craftsman's hands to hold the woodturning tools. The pedal was usually connected to a pole, often a straight-grained sapling. The system today is called the "spring pole" lathe (see Pole lathe). Spring pole lathes were in common use into the early 20th century. A two-person lathe, called a "great lathe", allowed a piece to turn continuously (like today's power lathes). A master would cut the wood while an apprentice turned the crank.^[1]

During the Industrial Revolution, mechanized power generated by water wheels or steam engines was transmitted to the lathe via line shafting, allowing faster and easier work. The design of lathes diverged between woodworking and metalworking to a greater extent than in previous centuries. Metalworking lathes evolved into heavier machines with thicker, more rigid parts. The application of lead screws, slide rests, and gearing produced commercially practical screw-cutting lathes. Between the late 19th and mid-20th centuries, individual electric motors at each lathe replaced line shafting as the power source. Beginning in the 1950s, servomechanisms were applied to the control of lathes and other machine tools via numerical control (NC), which often was coupled with computers to yield computerized numerical control (CNC). Today manually controlled and CNC lathes coexist in the manufacturing industries.

What is Lathe?

A lathe  is a machine tool which spins a block of material to perform various operations such as cutting, sanding, knurling, drilling, or deformation with tools that are applied to the work piece to create an object which has symmetry about an axis of rotation.

Lathes are used in woodturning, metalworking, metal spinning, and glass working. Lathes can be used to shape pottery, the best-known design being the potter's wheel. Most suitably equipped metalworking lathes can also be used to produce most solids of revolution, plane surfaces and screw threads or helices. Ornamental lathes can produce three-dimensional solids of incredible complexity. The material can be held in place by either one or two centers, at least one of which can be moved horizontally to accommodate varying material lengths. Other work holding methods include clamping the work about the axis of rotation using a chuck or cullet, or to a faceplate, using clamps or dogs.

Examples of objects that can be produced on a lathe include candlestick holders, cue sticks, table legs, bowls, baseball bats, musical instruments (especially woodwind instruments), crankshafts and camshafts.

Glossary of Lathe Terms

Apron	Front part of the carriage assembly on which the carriage hand wheel is mounted
Bed	Main supporting casting running the length of the lathe
Carriage	Assembly that moves the tool post and cutting tool along the ways
Carriage Hand wheel	A wheel with a handle used to move the carriage by hand by means of a rack and pinion drive
Chuck	A clamping device for holding work in the lathe or for holding drills in the tailstock. Drill chucks are sometimes referred to as Jacobs Chucks, a brand name that popularized that style of chuck.
Compound	Movable platform on which the tool post is mounted; can be set at an angle to the work piece. Also known as the compound slide and compound rest.
Compound Hand wheel	A wheel with a handle used to move the compound slide in and out. Also known as the compound feed.
Cross Feed	A hand wheel or crank that moves the cross-slide by turning a screw. Also the action of moving the cross slid using the cross feed hand wheel.
Cross-slide	Platform that moves perpendicular to the lathe axis under control of the cross-slide hand wheel
Half nut Lever	Lever to engage the carriage with the lead screw to move the carriage under power
Headstock	The main casting mounted on the left end of the bed, in which the spindle is mounted. Houses the spindle speed change gears.
Lead screw	Precision screw that runs the length of the bed. Used to drive the carriage under power for turning and thread cutting operations. Smaller lead screws are used within the cross-slide and compound to move those parts by precise amounts.
Spindle	Main rotating shaft on which the chuck or other work holding device is mounted. It is mounted in precision bearings and passes through the headstock.
Tailstock	Cast iron assembly that can slide along the ways and be locked in place. Used to hold long work in place or to mount a drill chuck for drilling into the end of the work.
Tailstock Hand wheel	A wheel with a handle used to move the tailstock ram in and out of the tailstock casting.
Tool post	A holding device mounted on the compound  into which the cutting tool is clamped
Ways	Precision ground surfaces along the top of the bed on which the saddle rides. The ways are precisely aligned with the centerline of the lathe.

 

 

 

  

 

 

 

 

 

Types of Lathe Machines

Wood Lathes

The simplest lathe type is the wood lathe. As the name suggests, it is designed for turning wood. Wood lathes are small machines consisting of a bed, headstock, tailstock and tool rest. There are no precision ways as are found on a metal-working machine, since the cutting tools are moved by hand and not by machine power. Great skill is needed to control the cutting tool to accurately turn smooth curves and complex contours on the work piece.

The spindle is usually driven by a belt connected to a motor, and speed changes are made by manually moving the belt to one of several pulleys mounted to the back of the spindle.

Lathe tools are held manually against the work, with the support of the tool rest. The tool rest is adjustable and is clamped to the bed at a position convenient for the operation at hand.  

Engine Lathes

Engine lathes are the classic metal turning workhorses of the production machine shop. They come in many sizes and are adaptable to working virtually any material. These machines have a longitudinal bed to which is mounted a headstock and tailstock.

As in the wood lathe, the headstock contains the spindle. However, the spindle drive is more complex, including variable speed capability or selectable gearing to provide a much wider range of speeds.

A carriage moves back forth on bed ways for longitudinal turning. A cross-slide and compound rest are mounted to the top of the carriage to provide cross and angular cutting capability.

The lathe cutting tools are moved against the work manually using hand wheels or automatically under the power of a lead screw that is driven by gears in the headstock.

         

 Tool room Lathe

The tool room lathe is a small- to medium-sized engine lathe specially designed for high-precision work. These machines find use in tool and die shops, where custom parts and precision fixtures are produced, often in support of production machining operations.

Tool room lathes are manufactured with special attention to spindle accuracy, smooth operation and precise alignment of the carriage and cross slide. A tool room lathe is capable of better accuracy and precision than a standard engine lathe.

Turret Lathe

Turret lathes are used in production machine shops where several sequential operations are needed on single work piece. It is costly and time consuming to remove a work piece from one machine and hold it in another. Removing and beholding a work piece also introduces errors in work alignment and machining accuracy.

The turret lathe has a rotating turret mounted to the carriage so that as soon as an operation with one tool is completed, the turret is indexed to bring another tool into working position. The part is then machined again without having to remove it from the chuck or collect. Eight (or more) different operations can be performed on a work piece using this type of machine.

CNC Lathe

Computer numerically controlled lathes have largely supplanted engine lathes in production machining environments. CNC lathes offer the advantages of greater powered axis drives, feedback control to monitor and maintain tool positioning and high-speed repeatability of complex machine motions. Once a program is verified, an operation can be quickly set up again without the need for tedious manual adjustments.

CNC lathes excel at cutting curved contours without the need for specially shaped tools. This is done by programmed variation of the speed of two motion axes and the spindle simultaneously---an operation that is impossible with an engine lathe.

Lathe Specifications

FEATURE	4000(4100)	4400(4410)
Swing over bed	3.50" (90 mm)	3.50" (90 mm)
Swing over carriage	1.75" (45 mm)	1.75" (45 mm)
Distance between centers	8.00" (200 mm)	17.00" (430 mm)
Hole through spindle	.405" (10 mm)	.405" (10 mm)
Spindle nose thread	3/4"-16 T.P.I.	3/4"-16 T.P.I .
Spindle nose taper	#1 Morse	#1 Morse
Travel of crosstie	4.25" (110 mm)	4.25" (110 mm)
Taper of tailstock spindle	#0 Morse	#0 Morse.
Protractor graduations	0° to 45° by 5°	0° to 45° by 5°
Hand wheel graduations	.001" (.01 mm)	.001" (.01 mm)
Length overall	24" (610 mm)	32.25" (820 mm)
Width overall	7.5" (190 mm)	8.75" (220 mm)
Height overall	6" (150 mm)	8" (200 mm)
Shipping weight	24 lb. (10.9 kg)	30 lb. (13.6 kg)
Motor/Speed Control	90 Volts DC with electronic speed control that accepts any incoming current from 100VAC to 240 VAC, 50 Hz or 60 Hz. Click here for more detailed motor and other machine specifications.
Spindle speed range	70-2800 RPM continuously variable by electronic speed control

Lathe Safety

1.      YOU are responsible for your own safety and proper machine operation.

2.      As small as it is, the mini lathe, like any power tool, can be dangerous if used improperly. If you are new to metal working, get in the habit right from the start of rigorously following good safety practices. Here are some tips:

3.      Always wear eye protection - preferably industrial quality safety glasses with side-shields. The lathe can throw off sharp, hot metal chips at considerable speed as well as spin off spirals of metal that can be quite hazardous. Don't take chances with your eyes.

4.      Wear short sleeve shirts, if possible, or shirts with snugly fitting cuffs if long sleeve. Loose sleeves can catch on rotating work and quickly pull your hand or arm into harm's way.

5.      Wear shoes - preferably leather work shoes - to protect your feet from sharp metal chips on the shop floor and from tools and chunks of metal that may get dropped.

6.      Remove wrist watches, necklaces, chains and other jewelry. It's a good idea even to remove your wedding ring since it can catch on rotating work and severely damage your ring finger and hand. 

7.      Tie back long hair so it can't get caught in the rotating work. Think about what happens to your face if your hair gets entangled.

8.      Always double check to make sure your work is securely clamped in the chuck or between centers before starting the lathe. Start the lathe at low speed and increase the speed gradually.

9.      Get in the habit of removing the chuck key immediately after use. Some users recommend never removing your hand from the chuck key when it is in the chuck. The chuck key can be a lethal projectile if the lathe is started with the chuck key in the chuck.

10.  Keep your fingers clear of the rotating work and cutting tools. This sounds obvious, but I am often tempted to break away metal spirals as they form at the cutting tool.

11.  Avoid reaching over the spinning chuck. For filing operations, hold the tang end of the file in your left hand so that your hand and arm are not above the spinning chuck.

Never use a file with a bare tang - the tang could be forced back into your wrist or palm.

Application

Ø  A CNC lathe is a machine tool designed to remove material from a rotating work piece, using a cutting tool. Some lathes can form hollow parts by a process called metal spinning. These parts have circular cross-sections. Metal and other materials can be turned on a lathe, including wood and plastics. CNC controlled lathes use a computer to control the process of making each part with repeated

Ø  A metal lathe usually spins the work piece along a horizontal axis. A mandrel or chuck is mounted to the Headstock of the lathe. A follower block or tail block is mounted to the tailstock. A blank piece is clamped to the

Ø  Lathe and pressure is applied to the blank via a cutting tool. Material is cut away on each pass across the blank.

Ø  After each pass, the lever arm is moved closer to the final position. Eventually, when the proper amount of material has been removed, the part is completed.

Ø  Yukawa AC drives can be interlocked with the CNC control systems so the operation of the CNC controller and the AC drive are synchronized.

Ø  In addition, the Energy Saving Mode in Yukawa AC drives automatically detect changes to the amount of torque required during shaping and finishing phases. This feedback enables the drive to quickly detect changes as the cutting tool becomes dull.

TECHNOLOGY FORECASTING

1. TECHNOLOGY  FORECASTING

Introduction:-

Technological forecast is a prediction of the future characteristics of useful machines, products, process, procedure or techniques. This implies following two points

1.         A technological forecast deals with certain characteristics such as levels of technical performances (eg. speed power, safety). Role of technological advances (introduction of paperless) office, picture phone new materials, costs, etc). The forecaster need not state how these characteristics will be achieved. His forecast may even predict characteristics which are beyond the present means of performing some of these functions .However ,it is not within his scope to suggest how these limitations will be overcome.

2.         Technological forecasting also deals with useful machines, procedures, or techniques. Technology forecast and technology innovation chain:-

    There are five stages of any technological innovations

           1.          Basic scientific findings /discovery of a principle:-

These establish minimum knowledge on basis of sound scientific principles from which a solution to specific problems could be found.

           

2.         Laboratory or bench level feasibility:-

At these stages depending on the identified problems, a laboratory workable model could be found /fabricated without violating any natural physical laws this would generally be able to work in the desired way only in laboratory environment, under control conditions and supervision of trained scientists, technology, and technician.

3.         Operating prototype /pilot plant:-

On reaching these stages it would be possible to obtain design/ engineering Parameters to construct a device/ system which would be capable of working in an operational environment using commercially available inputs.

4.         Commercial introduction /operational use:-

This stage represents not only technical and design adequacy, but also economical feasibility. Generally, first production model is benchmark of completion of this stage.

5.         Widespread adoption:-

At this stage having demonstrated the technical and /economic And / environmental superiority, the technology is now poised to supershed and replaces Prior devices, procedures, etc on a wide scale.

6.         Diffusion to other areas:-

At this stage new technology not only replaces old one ,but it is also adopted to perform such function as were not being performed by earlier devices techniques .

7.         Social and economic impact:-

At this stage, the innovations will affect the behaviour of the society and its use may reach point where its impact will be felt by society.

2. Necessity of technology forecasting:_

Historically US navy was one of major institutions which started formal technological forecasting to support the preparation of 15 year plan to identify likely opportunities and threats and to develop technological setting for future. Technology forecasting has now assumed importance in India due to structural reform introduced In our economic system with a view to create market driven economy. Essentially the Technology forecasting is used for purpose of

1.         scanning the technological environment

2.         anticipating emerging technological changes

3.         identifying suitable technologies by evaluating various alternatives

4.         scanning for technologies for future needs

We can identify four elements of forecast which can be specified and/or estimated. These are

1.         Time period 

2.         Nature of technology

3.         Characteristic to be exhibited by technology 

4.         Probability associated with characteristics

The time period may be stated generally or it may be given precisely The technology. Being forecast may be narrowly defined or it may encompass very broad range The characteristic may be stated only in general terms or may be given precise quantitative values The probability associated with characteristic may be given only generally, as high or low or it may be stated in precise quantitative terms and for each of these elements of forecast ,degree of precision may vary anywhere between two end points of generality and precision .The precision associated with each element of forecast should be determined by use to which forecast will be put The forecast should be thus tailored to the decisions making situation and precision associated with of the elements should be appropriate to this situations

 There may be three types of situations:-

1.         Absolutely no control

2.         Partial control

3.         Full control

We would attempt to analyses the efficacy of forecasting in the Situations.

1.         Absolutely no control :-

Let us consider a commuter seeking a forecast of the commercial availability of a solar powered car, say by year 2000. While he might seek the forecast out of simple curiosity, more likely he wants to make plans for some activity which will be affected by this forecast, say whether to buy a petrol driven car or not .Naturally he wants. To plan correctly, for if he bases his plans on a forecast of a solar or becoming wailable. And it does not materialize, the forecast has been useless to him or worse ,it has misled him into foregoing his buying a petrol car.

2.         Partial control:-

Most day to day decisions fall in the area of partial control over outcome .The decision maker is interested in influencing the out come of situation in away as favourable as possible to him .If he is presented with a forecast which he considers desirable, he will exert such control as he possesses to ensure that the forecast is realized, Thus influencing either reliability or time frame of the forecast.

3.         Full control:-

All the other extreme, when decision maker has complete control over the outcome, he does not even need a forecast The outcome will be what he wants it to be .Someone else may perhaps find a forecast of his decision useful, but he himself does not need a forecast of what he is going to do.

3. Role of technology forecasting

The forecast serves as an input to process of making plans and decisions. The role of forecast in is as follows:-

1.         The forecast identifies the limits beyond which it is not possible to go;

2.         It establishes feasible rates of progress, so that the plan can be made to take advantages of such rates; conversely it does not demand an impossible rate of progress.

3.         It describes the alternatives which are open and can be chosen from;

4.         It indicates possibilities which might be achieved; if desired;

5.         It provides a reference standard for a plan .The plan thus can be compared with the forecast at any point of time ,to determine  whether it can still be fulfilled or whether, because of changes in the forecast, it has to be changed, and

6.         It furnishes warning signals, which can alert the decision maker that it will not be possible to continue the present activities. Thus the purpose of the forecast is to be improving the quality of his decisions.

4. Classification of technology forecasting approaches

               There are two approaches to technology forecasting, namely

                1.     Exploratory

                2.     Normative

                  

                 1.    Exploratory forecasting  in to the future from the post performance or experience Its technology deals with the analysis of the technological  capability ,features etc of the past ,evaluation of the present ,looking forward to the future taking in to account the dynamic progression which brought us today’s  position .

2.    Unlike exploratory forecasting, the normative approach  begins from future and works out desired land works backwards to  the present state .In other words the mind is projected in to the future  by postulating  a desired  or possible state of technological  development to specify a specific need the forecaster then works backwards to identify the steps or landmarks necessary to be achieved with assessed level of probability, in order to reach end point or goal set hence fore

Thus the above two approaches are not competitive. They do not substitute one another. Essentially they are complementary to each other and have to be used together.

Methodologies of forecasting:-

Different techniques have been developed over the years to deal with forecasting methodologies .The forecaster has to judiciously select a techniques or a combinations of techniques depending on the methodology and the end objective in to view.

            Use of combination of methods will generally be more reliable than dependence on a single parameter or single forecasting methods. It may be useful to have the user of a technology, generator of a technology, manufacturer’s suppliers and designers involved in an integrated exercise to shape the combined perspective in to forecast.

5. TECHNOLOGICAL FORECASTING METHODS

            Some of the TF methods are now elaborated in this section

1.         Brain storming (BS)

            This is the oldest   method for forecasting it is conducted by a group of people to forecast about a specific technology by a collecting or contributing all the ideas spontaneously. The basis of the method is that the ideas should not be evaluated at the generation stage during many new ideas emerge. Thus, there is a separation of the idea generation and evaluation stages. The reason for this is that new ideas can emanate even people who even though not have through expertise in given field. The major objective of BS is to stimulate the generation of ides on given technology. It does not matter even if they are wild, highly impractical or exotic. Ideas are formed /offered spontaneously in a relatively unstructured environmental. After they have been presented, they analysed and evaluation is carried out in depth.

Steps involved in Brain Storming (B.S.) :-

1.         Identification of a person as a group leader .It is necessary that he is chosen by his age or his position or seniority or expertise in the technology, he must have the requisite experiences of integrating or channeling ideas to lead to solution.

2.         Identification of the problems by a group so that the multiple dimensions of the problems involved are carely highlighted

3.         Definition and redefinition of the problems so that it is unambiguously understood by the group possible solution are deliberately avoided.

4.         Idea generation process is initiated .Once number of ideas are collected, a number of triggering questions are initiated to help combine ideas or approaches.

5.         The recorded ideas are reviewed, classified and streamlined in to related ideas and clusters.

6.         Rearranged ideas are evaluated, possibly through reverse brainstorming that is the series of eliminating questions .Least favored ideas are rejected. Preferred once are analyzed and forecast are prepared in consultation with other functional efforts .The structure of the problem solving group is a major factor which determines the goodness of forecast .A group, to be effective, has to have a variety of people, such as

a.         Users of tech

b          Expert, knowledgeable in tech

c          Expert, knowledgeable in market

d          Economists /financials analysts

e          Dreamers with new ideas

f           Persuaders who can help acceptance of idea

g          Technology forecaster and consultants

            Based on experience it has been found out that the session could be structured, to some extent to facilitate the solution of the problem during BS .This in away involves first establishing a method for obtaining a variety of emergent ideas and then converging it on to the given solution.

Application of Brain storming (B.S.):-

            It has been applied to a wide rang of R&D, technological and business problem solving. This   method has been used for following purposes namely,

a)         for obtaining new ideas of products /processes /services /procedures

b)         for over coming new uses or market segments

c)         for over coming bottles necks

d)         for identifying alternative options or methods

       

             The group can have 5 to10 members. If there are more than 10 members, the processing of the proposed ideas become difficult. In some cases, the outsiders are used as leaders.   

Advantages and disadvantages:-

            The advantage of B.S. is that it is easy to organize and the resources needed are the modest. But it requires and experienced person to conduct it. A number of sessions are required since at the initial stages the participants are skeptical or hesitant sufficient time is needed for organizing a brainstorming exercise.

            Further, a considerable preparation has to be made before the actual exercise begins.

B)        Delphi technique:-

            Delphi is a programmed, sequential questionnaire approach. The word has its origin in once of Delphi in which a group of learned persons used to make forecasts. Instead of an individual making a forecast, a group prepares a forecast but with certain characteristics;

a)         Anonymity

b)         Iteration with controlled feed back and

C)        Statistical group response taking in to consideration minority views. The detailed steps involved in a Delphi exercise are as follows:-

1)         Identify the specific area or field in which Delphi exercise has to be carried out.

2)         Identify a set of user, technology generations /experts/equipment manufacturers, development bankers and social scientists and others who can help in preparing a set of questions for forecasting technological developments in the given area.

3)         A small core group is formed to prepare the questionnaire with the help of persons at step 2 to cover among other the desirability of the technological development, it feasibility, time frame and recourse needed for commercial use, and impact.

4)         The questionnaire is then administered to a number of participants to cover a wide cross–section of interests.

5)         The first round responses for the questionnaire is obtained and processed, where in minority and even extreme views etc. are also included.

6)         The second round questionnaire is sent back to the participants to give there revised comments.

7)         The second round result is than processed to get the consensus results.

            Thus, Delphi provides a consensus view based on the opinion of a large number of participants and can be considered as a way of combining /integrating forecasts.

Application of Delphi Technique:-

            The Delphi method is used to:-

a)         Identify new factor likely to influence the future sate of technological development;

b)         Obtain probabilistic estimates of technological performance over a specified time horizon;

c)         Obtain forecasts of a time scale foe an event where other methods can not be used;

d)         Ascertain the feasibility of a given event occurring under specified conditions; and

e)         Obtain subjective quantitative measures of technological performance in the absence of objective data.

                                   

            The preparation of the questionnaire has to be done very carefully and should, among other conditions, ensure that:-

a)         The issues are unambiguously specified

b)         The questions are un conditional and not interlinked to conditionality specified elsewhere

c)         The definition of probability for occurrence of an event etc. sought in a question should be clearly defined /explained.

Advantages:-

            It is a useful technique for

a)         Obtaining forecasts when there is a limited amount of historical data, and

b)         For fields which are highly interactive and interdisciplinary involving diverse parameters such as social, economic, political and managerial.

Disadvantages:-

                                         

a)         It does not have any logic underlying each prediction and if repeated, it may not 5 reproducible results and

b)         Although it may produce a high degree of convergence yet this convergence does not imply high degree of reliability.

   

6. Conclusion

            Today is an era of global competition & Companies are implementing new technique and methods to reduce cost of manufacturing and increase productivity and in turn profitability. One of the best solution to this problem is Technology Forecasting i.e. T.F.

            T.F is totally new approach which really worth and worth. It is a concept that goes beyond conventional method and approaches of maintenance activities. It provides new idea which can prevent further crisis.

            Both B.S. and D.T. if use successfully they provide new idea of activities that prevents quality defects breakdown, makes work easier.