Reamer Fitting Shop is related to assembly of parts, after bringing the dimension or shape to the required size or form, in order to secure the necessary fit.
The operations required for the same are usually carried out on a work bench, hence the term bench work is also added with the name fitting. The bench work and fitting plays an important role in engineering.
Although in today's industries most of the work is done by automatic machines which produces the jobs with good accuracy but still it (job) requires some hand operations called fitting operations.
The person working in the fitting shop is called fitter.
FITTING TOOLS: Fitting shop tools are classified as below:
I-Work Holding Devices/ Clamping Tools.
II-Measuring Tools
III-Marking Tools.
IV-Cutting Tools.
V-Striking Tools.
VI-Drilling Tools.
VII-Threading Tools.
I. WORK HOLDING DEVICES /CLAMPING TOOLS:
1. Work Bench: A fitting process can be done at various places, but most of the important operations of fitting are generally carried out on a table called work bench. The work bench is a strong, heavy and rigid table made up of hard wood. The size of the work bench required is about 150 to 180 cm length, nearly 90 cm width and approximately 76 to 84 cm height.
2. BENCH VICE: It is firmly fixed to the bench with the help of nuts and bolts. It consists of a cast Iron body and cast iron jaws. Two jaw plates are fitted on both the jaws. The holding surface of the jaw plates is knurled in order to increase the gipping. Jaw plates are made up of carbon steel and are wear resistant. One jaw is fixed to the body and the second slides on a square threaded screw with the help of a handle. The jaws are opened upto required length; job is placed in the two jaws and is fully tightened with the help of handle. Handle is used to move the movable jaw
3. V Block: In V Block, V grooves are provided to hold the round objects longitudinally. The screw of the clamp applies the holding pressure. When the handle is rotated there is movement in the screw.
II. MEASURING TOOLS
1. Steel Rule: These are made up of stainless steel and are available in many sizes ranging from 1/2 ft. to 2 ft. These are marked in inches or millimetres. All the faces are machined true. The edges of steel rule should be protected from rough handling.
2. Calipers: These are generally used to measure the inside or outside diameters. Different types are:
i. Outside Caliper: It is used to measure the outside dimensions. ii. Inside Caliper: It is used to measure the inside dimensions. iii. Spring Caliper: Spring is provided to apply the pressure and lock nut is provided to lock any desired position.
iv. Hermaphrodite, Jenny or Oddleg Caliper: One leg is bent at the tip inwardly and the other has a straight pointed end. It is used to scribe lines parallel to the straight edges.
3. Vernier Caliper: It is used for measuring the outer dimensions of round, flat, square components and also the inner size of the holes and bore. A narrow blade is used to measure the depth of bar slots etc. The reading accuracy in metric system is 0.02 mm and British system it is 0.001”. It is made of stainless steel
III. MARKING TOOLS:
1. Surface Plate: It is used for testing the flatness, trueness of the surfaces. It is made up of cast iron or graphite. Its upper face is planed to form a very smooth surface. It is also used in scribing work. While not in use, it should be covered with a wooden cover.
2. Angle Plate: It is made up of cast iron in different sizes; it has two planed surfaces at right angles to each other and has various slots in each surface to hold the work by means of bolts and clamps. Never do hammering on the angle plate to fasten (lighten) the nuts and bolts.
3. Scriber and Surface Gauge: It consists of a cast iron bass on the center of which a steel rod is fixed vertically. Scriber is made up of high carbon steel and is hardened from the front edge. It is used for locating the centres of round bars or for marking of the lines. Fig. Scriber and Surface Gauge
4. Punches: Punches are used for marking purposes. Dot punches are used for marking dotted line and centre punch is used to mark the centre of hole before drilling. Punches are made up of high carbon steel or high speed steels. One end is sharpened. Hammering is done on the second end while working. For dot punch, angle of the punching end is 60 degree while in centre punch; angle of punching end is 90 degree.
5. Try Square : It is used for checking squareness of two surfaces. It consists of a blade made up of steel, which is attached to a base at 90 degree. The base is made up of cast iron or steel. It is also used to mark the right angles and measuring straightness of surfaces. Never use try square as a hammer.
6. Vernier Height gauge: A Vernier height gauge consists of a heavy base, a graduated beam, a sliding head with Vernier sliding jaws holding the scriber and a fine adjustment clamp.
It is similar to large Vernier calipers in construction, except that it consists of a heavy base which allows the gauge to stand upright instead of a fixed jaw in a Vernier. The movable jaw of Vernier height gauge consists of a projection or extension which is levelled to sharp edge for scribing lines at any required height.
IV. CUTTING TOOLS -
1. Hacksaw: Hacksaw is used for cutting of rods, bars, pipes, flats etc. It consists of a frame, which is made from mild steel. The blade is placed inside the frame and is tightened with the help of a flange nut. The blade is made up of high carbon steel or high speed steel.
The points of the teeth are bent in a zig-zag fashion, to cut a wide groove and prevent the body of the blade from rubbing or jamming in the saw cut. The teeth of the blades are generally forward cut so in the case, pressure is applied in the forward direction only. Depending upon the direction of cut, blades are classified as: o Forward cut o Backward cut.
Depending upon the pitch of the teeth (Distance between the two consecutive teeth) blades is classified as:
Coarse (8-14 teeth per Inch)
Medium (16-20 teeth per inch)
Fine (24-32 teeth per inch)
2. Files: Files are multi points cutting tools. It is used to remove the material by rubbing it on the metals.
Files are available in a number of sizes, shapes and degree of coarseness.
Classification of files-
i. On the basis of length 4”,6”,8”,12”
ii. On the basis of grade:
Rough (R)(20 teeth per inch)
Bastard (B)(30 teeth per inch)
Second cut (Sc) (40 teeth per inch)
Smooth file (S)(50 teeth per inch)
Dead smooth (DS)(100 teeth per inch)
Rough and bastard files are the big cut files- When the material removal is more, these files are used. These files have bigger cut but the surface produced Is rough.
Dead smooth and smooth files have smaller teeth and used for finishing work.
Second cut file has degree of finish in between bastard and smooth file.
iii. On the basis of number of cuts:
Single cut files.
Double cut files.
Rasp files.
In single cut files the teeth are cut in parallel rows at an angle of 60 degree to the face.
Another row of teeth is added in opposite direction in case of double cut files. Material removal is more in case of double cut files.
iv. On the basis of shape and size:
The length of the files varies from 4' to 14*.
The various shapes of cross-section available ar5e hand file, flat file, triangular, round; square, half round, knife-edge, pillar, needle and mill file.
a. Flat file: This file has parallel edges for about two-thirds of the length and then it tapers in width and thickness. The faces are double cut while the edges are single cut.
b. Hand file: for a hand file the width is constant throughout, but the thickness tapers as given in flat file. Both faces are double cut and one edge is single cut. The remaining edge is kept uncut in order to use for filing a right-angled corner on one side only.
c. Square file: It has a square cross-section. It is parallel for two-thirds of its length and then tapers towards the tip. It is double cut on all sides. It is used for filing square corners and slots.
d. Triangular file: It has width either parallel throughout or upto middle and then tapered towards the tip. Its section is triangular (equilateral) and the three faces are double cut and the edges single cut. It is used for filing square shoulders or comers and for sharpening wood working saws.
e. Round file: It has round cross-section. It carries single cut teeth all round its surface. It is normally made tapered towards the tip and is frequently known as rat-tail file.
f.Parallel round files having same diameter throughout the length are also available. The round files are used for opening out holes, producing round comers, round-ended slots etc.
g. Half-round file: Its cross-section is not a true half circle but is only about one-third of a circle. The width of the file is either parallel throughout or upto middle and then tapered towards the tip. The flat side of this file is always a double cut and curved side has single cut. It is used for filing curved surfaces.
h. Knife edge file: It has a width tapered like a knife blade and it is also tapered towards the tip and thickness. It carries double cut teeth on the two broad faces and single cut teeth on the edge. It is used for finishing sharp corners of grooves and slots h. Diamond file: Its cross-section is like a diamond. It is used for special work.
i. Needle file: These are thin small files having a parallel tang and a thin, narrow and pointed blade made in different shapes of its cross-section to suit the particular need of the work. These are available in sizes from 100 mm to 200 mm of various shapes and cuts. These files are used for filing very thin and delicate work.
FILE CARD: It is a device fashioned like a wire brush used to clean dirt and chips from the teeth of a file. When particles of metal clog the teeth the file is said to the pinned, a condition that causes scratching of the surface of the work.
Files, therefore, require cleaning by means of a file card or by dislodging the material between the teeth by means of a piece of soft iron, copper, brass, tin plate and so on, sharpened at the end. Hardened steel should never be used
V-STRIKING Tools-
Striking tools have a wide use in fitting work like chipping, cutting and punching etc. These types of operations need striking on chisel and punch. Normally, this light type of striking is done by striking tools, known as hand hammer. All the hand hammers used in fitter’s work are similar in design to the smith’s hand hammers as such as ball peen, cross peen and straight peen etc. The only difference lies in weight. The hammers which are used in fitter’s work are comparatively lighter than the smith’s hand hammers.
Ball peen Hammer: The peen has a shape of ball which is hardened and polished. Particularly this type of hammer is used for riveting and chipping purpose.
Cross Peen Hammer: It is similar to ball peen hammer except the peen which is across the handle. It is mainly used for bending and hammering into shoulders etc.
Straight Peen Hammer: It has a peen straight with the handle that is parallel to the handle and is specially used for peening or stretching the meta
VI-Drilling Tools-
These tools are used for making hole in a given metallic piece. Drills are made of high carbon steel or high speed steel. All the drills are specified according to maximum size of hole that can be drilled by a drill.
There are three types of drill such as flat drill, straight fluted drill, and twist drill. All the three types of drill are shown in Figure 2.24. Generally, flat and straight fluted drills are not preferred in fitter’s work. They are simply used in carpentry work.
Twist Drill It is usually made of high speed steel. Twist drill has a cylindrical body carrying the spiral flutes cut on its surface. The drill should be ground with both lips at 59˚ to the axis of drill so that the lip angle or cutting angle may be obtained 118˚, i.e. the best cutting angle.
Reamer- It is used just to finish a drilled hole or to bring it to the correct size as shown in Figure 2.2
It consists of two main parts which are Shank and Body. The hand reamer has a square shank for holding in a tap wrench. Body is also in cylindrical shape carrying straight flutes cut on its surface. Reamers are made of high speed or high carbon steel.
VII-THREADING Tool-
Die - It is used for cutting external thread on a cylindrical surface such as bolt and stud etc. Dies are made of high carbon or high speed steel.
Two types of dies – solid die and adjustable or slip die – are in common use these days.
Different Types of Die-
Solid die has fixed dimension and cannot be adjusted for larger and smaller diameter.
Adjustable Die means it can be set to cut larger or smaller diameter. The tool used for holding the die is known as die-stock.
Tap It is used for cutting internal thread in a cylindrical hollow surface such as nut and hollow shaft. Taps are also made of high carbon or high speed steel.
Hand Taps are usually made in sets of three pieces. They are usually known as taper, second or intermediate and plug or bottoming.
Taper tap is used to start the thread so that the threads are formed gradually. Tapered surface of this tap enables the tap to enter the hole easily.
After full length of the toothed body of the tap has been screwed down in the hole, this is withdrawn and then follows the intermediate tap. It is also screwed down to its full length and thus the threads are cut and finished to the desired size.
Plug or bottoming tap is especially used to cut the threads in a blind hole. Tool used for holding the taps is known as tap wrench.
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