Lesson No. 11 Week No. 07 Name of lesson Marking Tools

STEEL RULE Use:- for linear measurement and marking. Material:- spring steel or stainless steel. Graduation:- in 10mm, 5mm, 1mm and 0.5mm in metric system. The reading accuracy of the steel rule is 0.5mm. Size:- available in 150mm, 300mm & 600mm.

TRY SQUARE Use:- to check the squareness of machined surface, flatness of surface, make lines at 90º to the edge of work pieces & to set work piece at right angle on work holding device. Material:- hardened steel. Size:- available in 100mm, 150mm & 200mm. Types:- 1. Fixed try square 2. Adjustable try square Blade 90º Stock

CALIPER CALIPER:- Calipers are simple measuring entinstrum used to transfer measurement from steel rule to objects and vice versa. They are made from tools steel or high carbon steel. Outside Caliper Firm joint caliper:- In the cage of firm joint caliper, both legs are pivoted at one end. To take measurement of a work piece, the caliper is opened roughly to the required size. Fine setting is done by tapping the caliper lightly on a wooden surface.

2. Spring joint caliper:- For this type of caliper, the legs are assembled by means of a pivot loaded with a spring. For opening and closing the caliper legs, a screw and nut are provided. Spring joint caliper have the advantage of quick setting. The setting made will not change unless the nut is turned. The size of caliper is specified by its length, which is the distance between the pivot centre and the tip of the leg. Spring Pivot Adjusting Unit

Inside Caliper Inside Caliper:- This caliper is used to measure the inside dimensions like the width of slots, diameter of holes, etc. Legs of this caliper are bent in outward direction as shown in figure beside.

Odd leg Caliper:- This caliper is also known as Jenny caliper or Hermaphrodite caliper or leg and point caliper.They are used for marking lines parallel to inside and outside edges, locating the centre of round bars, drawing parallel lines along outer edges, scribing lines along curved edges.

DIVIDER Use:- for scribing circles, arcs and transferring and stepping of distances. Material:- tool steel or high carbon steel. Size:- 50mm to 200mm.

For the correct location and setting of the divider legs, prick punch marks of 30º are used. Both the legs of the divider should always be of equal length. Dividers are specified by the type of their joints and length. The divider point should be kept sharp in order to produce fine lines. Frequent sharpening with an oil stone is better than sharpening by grinding. Sharpening by grinding will make the points soft. Firm Joint

PUNCH Use:- Punches are used in order to make certain dimensional feature of the layout permanent. Material:- They are made of high carbon steel. Types:- 1. Centre punch(90º) 2. Dot punch(60º) 3. Prick punch(30º)

1. Centre Punch:- The angle of the point is 90º 1. Centre Punch:- The angle of the point is 90º. The punch mark made by this is wide and not very deep. This punch is used for locating hole. The wide punch mark gives a good seating for starting the drill. Centre Punch 2. Dot Punch:- The angle of the point is 60º. This punch is used for marking witness marks. Dot Punch

Prick Punch 3. Prick Punch:- The angle of the point is 30º. The 30º point punch is used for making light punch marks needed to position dividers. The divider leg will get a proper seating in the punch mark.

SCRIBER Use:- scribe lines to indicate the dimensions of the work piece to be filed or machined. Material:- They are made of high carbon steel. Types:- 1. Single ended 2. Double ended 3. Knife edge 4. Off-set. 1. Single ended:- This scriber is also known as Hand scriber. Point is made on one side only. Knurling is made on the body of this scriber. It is used for general marking purposes.

Straight Point 2. Double ended:- This scriber has one point each at both ends. One of which is bent at 90º, another point is kept straight. Centre portion of body is knurled for better gripping. This scriber is used mainly in accordance with scribing block. Grip Bent Point

3. Knife edge:- This scriber has one point each at both ends 3. Knife edge:- This scriber has one point each at both ends. One of which is knife edge, another point is kept straight. Centre portion of body is knurled for better gripping. This scriber is used mainly for plastic and wood working 4. Off-set:- Point of this scriber is made offset to facilitate the marking of minimum height and to set zero when used with Vernier Height Gauge.

SCRIBING BLOCK Use:- It is used for ; - - Scribing lines parallel to a datum surface. - - Setting job on machines parallel to a datum surface. - Checking the height and parallelism of jobs, setting jobs concentric to the machine spindle Types:- 1. Fixed scribing block 2. Universal scribing block.

Fixed Scribing Block Scriber 1. Fixed Scribing Block:- The fixed type of surface gauges consists of a heavy flat base and a spindle, fixed upright, to which a scriber attached with a snug and a clamp nut. Snug Nut Spindle Base

Universal Scribing Block 2. Universal Scribing Block:- This surface gauge has the following additional features; The spindle can be set to any position. - Fine adjustments can be made quickly. - Can also be used on cylindrical surfaces. - Parallel lines can be scribed from any datum edge with the help of guide pins. Spindle Scriber Snug Nut Fine adj. screw Base Rocker arm Guide Pin

ANGLE PLATE Use:- To support the job and to provide a vertical or angular plane for marking. Material:- Angle plates are made from Cast iron or Steel. Types:- 1. Solid Angle plate 2. Adjustable Angle Plate 3. Box Angle plate.

Solid Angle Plate:- This angle plate is most common Solid Angle Plate:- This angle plate is most common. It has the two plane surfaces perfectly machined at 90º to each other. Such angle plates are suitable for supporting work pieces during layout work. They are comparatively smaller in size. Slots are provided to clamp the work piece and to reduce the weight.

Adjustable Angle Plate:- This angle plate is available to support job in different angles. Graduations are marked on it to set the job at particular angle. Slots are provided on it to clamp the job by clamping bolts. They are available in Grade-I and Grade-II

Box Angle Plate:- They have applications similar to those of other angle plates. After setting, the work can be turned over with the box enabling further marking out or machining. This is a significant advantage. This has all the faces machined square to each other.

SURFACE PLATE Use:- Surface plates are used most widely as a datum surface in machine shop work. Material:- Gray cast iron and Granite. Specification:- Cast iron surface plates are designated by their length, breadth, grade and the Indian Standard number. i.e. C.I. Surface plate 2000 X 1000 Gr1. I.S. 2285.

SURFACE PLATE TOP Heavy Ribs BOTTOM 3 Point suspension

CONCLUS ION Thus we get the knowledge of Calipers, Trysquare, Punch, Scriber, Marking Block, Surface plate, Angle plate.

QUESTIONS List the types of Marking tools ? What are the types of Calipers? What is the use of Scriber ? What is the use of Try square ?