Chapter 11

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Layout Work and Safety IssuesUNIT 11 LAYOUT WORK AND SAFETY

ISSUES Structure

11.1 Introduction Objectives

11.2 Method of Laying Out Angles 11.2.1 Angular Layout by using a Ruler 11.2.2 Angular Layout using an Adjustable Square 11.2.3 Angular Layout using Bevel Protractor

11.3 Laying Out an External Radius

11.4 Laying Out an Internal Radius

11.5 Layout Out Hole Locations using Test and Proof Circles

11.6 Layout Operation

11.7 To Layout Hole Locations, Slots and Radii

11.8 Safety Issues in Tool Engineering and Management

11.9 Summary

11.10 Key Words

11.1 INTRODUCTION

It is necessary for an operator to layout a workpiece so that the lay out lines will provide guideline during the machining process. Most of the layouts consist of scribing straight lines, circles, arcs, and angles on the surface of a workpiece. There are many ways to layout work and the method use will depend upon the accuracy required and availability of the tools.

Objectives After completing this unit, you should be able to understand

• scribing the angle by the rule, bevel protractor, universal bevel protractor,

• choosing the proper method of angular layout,

• layout circle and arc by using dividers and trammels, and

• layout hole locations using test circles.

11.2 METHOD OF LAYING OUT ANGLES

Angular layout involves the use of straight layout lines. These lines are positioned by using a rule, a bevel protractor or universal bevel protractor.

11.2.1 Angular Layout by Using a Ruler This form of angular layout is usually not shown as an angle on the drawing. It merely shows the distance from a corner along the two adjacent sides. Figure 11.1 shows a typical layout using a ruler. The corner A is the only one that doesn’t show an angular dimension.

The procedure for laying out angle by using a ruler is as follows :

(a) Remove all burrs and clean the face of the workpiece.

(b) Apply the layout dye to the surface to be laid out.

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(c) Measure 1cm from the corner along the two sides by using a ruler and scribe the line on each edge.

Layout Design for Tool Engineering

(d) Join these points with the edge of the ruler.

(e) Lightly mark this line at interval of 6 to 9 mm by using prick punch.

1/8 2 Holes

Figure 1.1 : Layout

11.2.2 Angular Layout Using an Adjustable Square The angle at corner A is indicated in degrees without any tolerance as shown in Figure11.1. An angle of 45o on the body of the adjustable square is accurate enough to be used for laying out this angle.

(a) Scribe a short line 1 cm from the corner along the end.

(b) Place the ruler in adjustable square and lock it in position.

(c) Place the body of the square against the end and slide it along until the edge of the ruler is over the mark on the workpiece.

(d) Hold it firmly in this position and scribe a line along the edge of the ruler.


11.2.3 Angular Layout Using Bevel Protractor An angle at corner C is indicated in the degrees. This indicates that a bevel protractor can be used for laying out this angle.

(a) Scribe a short line 2 cm from the end along the side.

(b) Set the bevel protractor at 30o.

(c) Place the body of the square against the end and slide it along until the edge of the ruler is over the mark on the workpiece.

(d) Hold it firmly in this position and scribe a line along the edge of the ruler.


SAQ 1 (a) Explain various methods of laying out of angles?

(b) Explain in detail laying out of angles by bevel protractor.

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Layout Work and Safety Issues11.3 LAYING OUT AN EXTERNAL RADIUS

An external convex radius is generally found on the corners or the edge of the workpiece. The radius (corner D), shown in Figure 11.1, requires that a quarter of a circle having 1 cm radius must be laid out on the workpiece.

(a) Set an adjustable square to 1 cm.

(b) Locate the center of the quarter; in such a way that center will be at 1 cm from the edge and the end, by scribing intersecting lines at this point.

(c) Mark this intersection point by prick punch.

(d) Set the dividers to 1 cm.

(e) Scribe the arc which should just touch the two adjacent edges of the workpiece at a point 1 cm along each side.

(f) Mark this point by prick punch.

SAQ 2 How external radius can be laid?

11.4 LAYING OUT AN INTERNAL RADIUS

Internal radius or corner radius is shown in Figure 11.1 at corner E. The laying out internal radius by divider is quite tedious work because it is necessary to position the point of the divider on the edge of the workpiece. A block of metal or wood held against the edge of the work will make the job much easier. If the workpiece is of steel or cast iron, a magnet placed on the edge will work well.

(a) Clean the edge of the workpiece and remove all burrs.

(b) Mark off the position of the center of the internal radius 8 cm from the corner.

(c) Set the divider to 2 cm.

(d) Place the magnet on the edge of the workpiece at the marked position. Or, hold the flat metal or wooden block against the edge of the work at this point.

(e) Place the point of the divider on the mark and in the small groove between the magnet and the work.

(f) Scribe a semicircle, do not allow the point of the divider to slip out of the position.

(g) Mark this arc by the prick punch.

SAQ 3 Explain laying out of an internal radius.

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Layout Design for Tool Engineering 11.5 LAYING OUT HOLE LOCATIONS USING TEST AND

PROOF CIRCLES

When the hole location is required to be accurate, the position of the hole must first be laid out and then test and proof circles should be scribed to indicate the exact position of the hole. Test circles are scribed on the workpiece to show the operator about the relation of the drill point to the location of the hole. This permits the drill point location to be moved over, if necessary, before drill cuts to the full diameter.

Figure 11.2 : Layout Showing Test and Proof Circle

(a) Place the workpiece on the edge against the angle plate.

(b) Scribe a center of diameter 4 cm from one side of the workpiece with the surface gauge.

(c) Rotate the workpiece by 90o and scribe another line intersecting the first.

(d) Set the surface gauge to 8 cm and scribe another line intersecting the first.

(e) Mark the intersection of these lines by the prick punch.

(f) Set the divider to 2 cm and scribe two circles of the diameter 4 cm. These are proof circles and indicate the location of the hole. Figures 11.2 and 11.3 shows the layout showing test and proof circles.

Test Circle

Proof Circle

Figure 11.3 : Steps in Layout Out Test and Proof Circle

(a) Set the divider to 1 cm and using the same center points, scribe the circle inside each of the other circles. These are the test circles and will indicate whether the drill point is central with the proof before it reaches the full diameter.

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Layout Work and Safety Issues

(b) Place four light punch marks on both sets of circles at the intersection of the lines if the circles are of diameter under 2 cm. If the diameters of circles are over 2 cm, eight equally spaced punch marks should be made. The punch in proof circle will indicate whether the hole has been drilled in the proper location.

SAQ 4 What is test and proof circle? Where and how do you use these circles?

11.6 LAYOUT OPERATION

The layout is not same for all the workpieces, but there is a procedure which should be followed in making layout. It is recommended that lines will be laid out in following order during laying out :

(a) Horizontal lines and centerlines.

(b) Vertical and intersecting lines.

(c) Arcs and circles.

(d) Straight line, connecting arcs and circles. (It is much easier to connect the line to circle or arc than connecting the circle or arc to line).

(e) Angular layout lines.

SAQ 5 List the recommended order of laying out the lines.

11.7 TO LAYOUT HOLE LOCATIONS, SLOTS AND RADII

Following are the steps involved in laying out the hole locations, slots and radii :

(a) Study Figure 11.4 and select proper stock.

(b) Cut off the stock, allowing enough material to square the ends if required.

(c) Remove all burrs.

(d) Clean the surface thoroughly, and apply lay out dies.

(e) Place a suitable angle plate on a surface plate.

Figure 11.4 : Layout

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(f) Clamp the work to the angle plate with a finished edge of the part against the surface plate. This is known as the reference surface. Leave one end of the angle plate protruding beyond the workpiece. (All measurement for any location must be taken from the base line or finished edge).


(g) Scribe the centerline as shown in Figure 11.5 for full length of the workpiece with the surface gauge set to the proper height.

Figure 11.5 : Lines Scribed Parallel to the Base

(h) Set the surface gauge as required and scribe the centerlines for all hole and radii locations using centerline as a reference. The scribing of centerline for holes is shown in Figure 11.5.

(i) Turn the angle plate by 900 and scribe the base line at the bottom of the workpiece as shown in Figure 11.6.

(j) Locate and scribe the other centerlines for each hole or arc using baseline as a reference line. Location and scribing of other centerlines is shown in Figure 11.6.

Figure 11.6 : Lines Scribed Parallel to the Base

(k) Locate the starting point for the angular layout.

(l) Remove the workpiece from the angle plate.

(m) Mark the center of all holes by prick punch with care.

(n) Scribe all circles and arcs using divider set as shown in Figure 11.7.

Figure 11.7 : Circles and Arcs Scribed

(o) Scribe any line required to connect arcs or circles as shown in Figure 11.8.

(p) Draw the angular lines as shown in Figure 11.8.

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Figure 11.8 : Arcs and Circles Connected by Straight Line

SAQ 6 How do you lay out the hole locations, slots and radii?

11.8 SAFETY ISSUES IN TOOL ENGINEERING AND MANAGEMENT

Hand and machine tools are dangerous if used improperly or carelessly. A person operating the machine tools must be aware of the safety rules and necessary precaution for each tool to avoid any accident. The main cause of accident is carelessness in working area.

11.8.1 Prevention of Accident It takes many years to become expert operator and one moment of carelessness may cause severe damage. Since accidents can be avoided, a person learning the machine shop trade must first develop safe work practice :

(a) Be neat and tidy all the time.

(b) Build personal responsibility.

(c) Learn to consider the welfare of fellow workers.

(d) Derive satisfaction from performing work accurately and safely.

Safety in machine shop is generally divided into four categories : Personal grooming, housekeeping, handling tools and materials, and operating machine tools.

Personal Grooming

Many accidents in machine shop are caused by careless habit of worker. The major causes of accidents are lack of proper eye care, loose or improper clothing, personal grooming, horseplay etc.

The accidents can be prevented by :

(a) Wearing safety glasses or goggles during working in machine shop to protect eyes. Glasses with side shield provide better eye protection. Chips may fly to a great distance during metal cutting operation; hence it is necessary to wear glasses. Many hand cutting tools are made of hardened steel, which can break due to the excessive force; hence it is wise to wear safety glasses in machine shop.

(b) Never wear loose clothing while working around any machine. Loose clothing may come in between revolving parts of machinery. Hence it is generally recommended that fold the sleeves of shirt up to the elbow and ties be removed. Also sweater with long hair should not be worn in a machine shop.

(c) Always wear footwear in machine shop because the sharp edge chips are produced during metal cutting operation. Therefore, it is necessary to wear at least leather shoe to avoid any accident. Sandals and sport

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shoes don’t offer any protection for the feet and should never be worn.

(d) Long hair must be protected by a hair net. Long hair may come in between revolving drill. It can cause serious head injury.

(e) Remove bracelets, watches, rings. Jewellery should never be worn in machine shop, since these items can be caught in the machine and draw a finger or entire hand in the machine. If ring is worn by operator and heavy piece of steel fall on hand, the ring may bend and cut the finger.

(f) Always avoid horseplay as the tools are sharp and machines are made of steel, which is hard. An accidental slip or fall can cause serious body injury. In many industry workers are dismissed because of horseplay as many accident has occurred in the past.

(g) Never use compressed air to clean machines. Sharp chip can fly to a great distance when blown by compressed air. This can be hazardous to a person cleaning the machine and also to the other workers as well.

House Keeping

Poor housekeeping has resulted number of accidents in a machine shop. Good housekeeping will not only provide safe working conditions but also improve efficient of the job.

These accidents can be prevented by :

(a) Keep the floor around a machine free of tools and raw materials. Tripping over material which is lying on floor, especially round bars can cause dangerous injuries. Make sure that area around a machine is neat and clean so that operator can move safely.

(b) Keep the floor free from oil and grease. If oil, grease, cutting fluids is dropped on the floor, be sure to remove the same as early as possible to prevent dangerous fall.

(c) Sweep up metal chips from the floor frequently. Sharp Metal chips quickly embedded in the soles of shoe. Sole of shoe become slippery due to these chips and further cause dangerous fall.

(d) Always keep machine clean. The clean machine will provide pleasant working environment during operation. Always use brush to remove metal chips from machines. Oily surface should be cleaned by jute clothes.

(e) Always stop a machine before trying to clean it. If machinist try to clean the machine during operation, it may result in severe injury. A rag can easily be caught in the revolving work or part of a machine and draw the entire hand in a machine. Thus, It is wise to shut off the main switch for cleaning purpose.

Operating Machine Tools

The safety measures may vary from for different cutting tools to different machining procedures. Still, there are some common safety rules which should be religiously practiced during the operation of machine tool.

These accidents are prevented by :

(a) Never try to operate the machine tool until one is fully conversant with its mechanism.

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(b) Ensure that all the safety guards are in place before starting any machine tool.

(c) Never wear loose clothing around machine tool.

(d) Keep your hands away from moving parts of the machine.

(e) Always wear safety glasses in a machine shop, especially when operating machine tool.

(f) Stop the machine before trying to clean it or to measure the dimension of the workpiece.

Handling Tools and Material

Many serious cuts are caused by handling sharp tools or material improperly. Similarly, permanent back injury can be resulted due to improper lifting techniques.

These accidents can be prevented by :

(a) Always remove the burr or sharp edges from workpiece. Sharp edges are hazardous. Whenever part is to be removed from a machine, ensure to remove burrs with a file.

(b) Never handle sharp tools or cutters by hand. When handling sharp tools such as milling cutters, it is wise to use a rag to avoid cuts if they should have tendency to slip.

(c) Use proper lifting techniques for lifting tools and materials. Many back injuries have been caused by improper lifting of heavy workpieces. The method of lifting material is as follows :

(i) Seat on your heels, bending your knees and make sure that your back is straight.

(ii) Grasp the material securely and use your leg muscles to raise the load. Keep your back straight; bending the back can put excessive strain on it.

(iii) Lower the material to the floor by bending the knees.

SAQ 7 (a) What are various causes of accident?

(b) Discuss the various safety norms in the industry.

11.9 SUMMARY

It is necessary for an operator to layout a workpiece so that the layout lines will provide guideline during the machining process. This unit deals with scribing angles, internal and external radius. Bevel protractors, rules, adjustable square are used for laying out angle. Holes are located by means of test and proof circles. Accident is generally caused by carelessness in working area. The safety in machine shop is divided into four groups: personal grooming, house keeping, operational machine tool and handling tools and material. Many accidents in machine shop are caused by careless habit of worker. Poor housekeeping has resulted number of accidents in a machine shop. Good housekeeping will not only provide safe working conditions but also improve efficiency of the job. Permanent back injury can result from using improper lifting techniques. Hence it is necessary to follow safety precaution while operating any machine.

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Layout Design for Tool Engineering 11.10 KEY WORDS

Bevel Protractor : The bevel protractor is used to layout and check the angle.

Proof Circle and Test Circle : Used to scribe the exact position of the hole.

FURTHER READINGS Kibbe R. R, Neelay J. E., Meyer R. O., White W. T., Machine Tool Practices, Prentice Hall Publication, New Jersey.

LAYOUT DESIGN FOR TOOL ENGINEERING Layout Work and Safety Issues

Layout is very important for cutting the stock, filing, grinding, drilling and milling etc. Before cutting operations, layouting is an essential operation in machine shop. This block, comprising 3 units, will be discussing about tools required for basic layout, various types of basic layout operations and layout work and safety issues.

Unit 9 explains the concepts of layout operations, and tools required for layout. It also describes the necessity for accurate layout and purpose of layout tools.

Unit 10 deals with the preparation of layout surfaces, layout parallel tones to an edge and layout lines at right angles. It also explains the concepts of checking the accuracy of the centre layout.

Finally Unit 11 discusses the various methods of laying out angles and laying out internal and external radii. Lastly it concludes with briefing on some safety issues in tool engineering.

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Chapter 11