ANGLE PLATES-SURFACE PLATES-MARKING MEDIA-FITTER ONLINE NOTE

1. MARKING

i)- If we have decided to construct a house then according to size of plot its design is kept in mind and accordingly its map is prepared .

ii)- Then i have a layout plan or make a marking on the plot. 

iii)- If without marking it is built, then it may not be good. 

iv)- Similarly before making any job its marking or layout according to the drawing or blue print should be done. 

v)- If not done like this then job may not be correct and accurate.

vi)- Marking on the job as per blue print is known as layout or marking out. 

vii)- The most important step in the marking of a machine part.

viii)- The particular fitting operation is the marking or layout of guidelines on the metal before machining or cutting by hand tools.

PURPOSES OF MARKING

1)- It acts as guidelines during making of job by the worker with the result he can make the job quickly and correct in sizes.

2)- Marking save the time because worker knows the quantity to be cut by machine or file.

3)- After marking it is not necessary to check the job frequently.

4)- Worker will know the sequence of operation to be carried out after marking.

DIFFERENT MARKING MEDIA 

The different marking media are A)- Whitewash, B)- Marking blue, C)- Prussian Blue, 

D)- Copper Sulphate and E)- Cellulose Lacquer. 

A)- Whitewash:-  

i)- There are so many methods to make it like chalk and water, chalk and spirit and white lead with tarpin oil.

ii)- Remember white wash is used for rough, rusty or mild steel jobs and not for finishing job.

B)- Marking blue:- 

i)- A Chemical dye, blue based colour mixed with methylated spirit used for marking on workpieces which are reasonably machined surface.

C)- Prussian Blue:- 

i)- This is used on filed or machine-finished surfaces. 

ii)- This will give very clear lines but takes more time for drying  than  the other marking media.

iii)- It is normally used on machining or filing surface. 

iv)- The lines drawn with this looks bright and clear.

v)- Today it requires more time and during work it may wash out on

D)- Copper Sulphate:-

i)- The solution is prepared by mixing copper sulphate water and a few drops of nitric acid.

ii)- The copper sulphate is used on filed or machine-finished surfaces.

iii)- Copper sulphate needs to be handled carfully as it is poisonous.

iv)- Do not use the job in wet condition having solution of nitric acid, wait till it dry then only start marking on it otherwise it will spoil the marking tool.

E)- Cellulose Lacquer:- 

 i)- This is a commercially available marking medium. 

ii)- It is made in different colours and dries very quickly.

iii)- Its lines look very bright and clear.

iv)- It is the best marking material or media. 

2. SURFACE PLATES

i)- When accurate dimensional features are to be marked by surface plate.

ii)- It is essential to have a datum plane with a perfectly flat surface. 

iii)- Surface plates are generally made of good quality cast iron.

iv)- Its available in three grades - Grades 1, 2 and 3.  

v)- The grade 1 surface plate is  more acceptable than the other two grades. 

vi)- Specifications of Cast iron surface plates are designated by their length, breadth, grade and the Indian Standard number. 

v)- For example:- Cast iron surface plate 2000 x 1000 Gr 1. I.S. 2285.

TYPES OF SURFACE PLATE ACCORDING TO MATERIAL 

(A) Cast Iron Surface Plate: 

I)- Surface plate is normally made of close grained cast iron. 

ii)- Two mild steel handles for lifting are attached to it. 

iii)- The edges of surface plate is bigger than its base so that job can be clamped with these as and when required.

iv)- Its upper surface is very accurately made by scraping and machining. 

v)- Its accuracy is classified in grades like ' A' grade

vi)- surface plate is used for marking with precision instrument by placing the job over the surface plate. 

vii)- It is also used for setting and measuring purposes. 

viii)- Its accuracy is 0.005 mm and ' B' grade plate has 0.02 mm accuracy which can be tested by dial test indicator. 

ix)- The surface plate is always designed for perpendicular from its adjoining four sides. 

x)- Cast iron base is fixed to its bottom and its below surface is made plain by with the help of machine. 

xi)- It is placed horizontally over the rigid support so that it should be at working height from the ground level. 

xii)- It is used to level the flat surfaces, checking of try square accuracy during angle plate marking, surface gauge and ' V'block smooth base.

B) Granite Surface Plate:- 

i)- It is made from stone called granite. 

ii)- It is rust proof and has no effect of heat and temperature.

iii)- There will be no effect on its accuracy if any scratch is made while working. 

iv)- According to work it is available in different sizes.

C) Glass Surface Plate:- 

i)- The surface plates made of glass are available in different sizes like 15 cm x 15 cm to 60 cm x 90 cm.

ii)- Accuracy up to 0.004 to 0.008 mm. 

iii)- It has no effect of rust. 

iv)- According to working these are available in different shapes and sizes. 

v)- It is used for small work. 

Advantages:

1. It is light in weight,

2. It is free from burning.

3. It is free from rust and no effect of environment.

4. Its accuracy last long.

Care & maintenance:-

i)- Clean before and after use.

ii)- Do not keep job on the surface plate.

iii)- Don't keep any cutting tool on the table.

3. ANGLE PLATES

i)- Angle plates have two plane surfaces and machined perfectly flat and at right angles.

ii)-  Generally these are made of closely grained cast iron or steel.

iii)- Angle plates are available in two grades - Grade 1 and Grade 2.

iv)- Care & Maintenance- a)- Clean before and after use. b)- Apply oil after the use.

Specification of angle plates:- 

a) Size 6 Grade 1 Box plate will be designated as - box angle plate-No 6 /Gr 1 / IS 623. 

b) Size 2 - Grade 2 angle plate will be designated as Angle plate- No2 / Gr 2 / I.S 623. 

Types of angle plates:-

a)- Plain solid angle plate, b)- Slotted type angle plate, c)- Swivel type angle plate, d)- Box angle plate.

a)- Plain solid angle plate:-

 i)- The plain solid angle plate is the most common.  

ii)- It has the two plane surfaces perfectly machined at 90° to each other. 

iii)- Such angle plates are suitable for supporting work-pieces during layout work.  

iv)- They are comparatively smaller in size. 

b)- Slotted type angle plate:-

i)- The two plane surfaces of  this type of angle plate have slots milled.  

ii)- It is comparatively bigger in size than the plain solid angle plate.

iii)- The slots are machined on the top plane surfaces for accommodating clamping bolts.

c)- Swivel type angle plate:-

i)- This is adjustable so that the two surfaces can be kept at an angle.  

ii)- The two machined surfaces are on two separate pieces which are assembled. 

iii)- Graduations are marked on one to indicate the angle of tilt with respect to the other. 

iv)- When both zeros coincide, the two plane surfaces are at 90° to each other. 

v)- A bolt and nut are provided for locking in position.

 d)- Box angle plate:-

i)- They have applications similar to those of other angle plates. 

ii)- After setting, the work can be turned over with the box enabling further marking out or machining. 

iii)- This is a significant advantage. 

iv)- This has all the faces machined square to each other.