Introduction
Bench working involves the use of hand tool for performing various operations such as cutting, scraping, threading etc. on metal pieces. Fitting involves aligning and assembling of finished parts in position.
The operation results into some assembly of machine Fitting work involves bench working operation for cutting and finishing the metal parts to ensure required fit between the mating components to fulfill functional requirements during service.
Tools
Tools may be defined as the device used to carry out different operations in fitting shop like cutting, filling etc. Tools may be classified further into following types on the basis of applications of tools.
(1) Holding Device:
It is used holding the job in appropriate position firmly.
Vice: The job is supported and holding in between the jaws. The vice may be classified in to following types.
(a) Parallel jaw bench vice
(b) Pipe vice
(C) Leg vice
(d) Hand vice
(e) Machine vice
(f) Pin vice
Parallel Jaw Bench Vice: This vice is generally used after mounting on bench and its jaws are parallel to each other. Generally, it is used to support and holding jobs during filing, chipping and hack sawing etc. The main parts of parallel jaw bench vice are.
(a) Fixed jaw (Grey cast iron)
(b) Movable jaw (grey cast iron)
(c) Jaw Plate (tool steel)
(d) Spindle (mild steel)
(e) Handle (mild steel)
(f) Box nut (gun metal)
(2) Measuring Tools:
This tools used for taking measurement or checking dimensions are called measurement device. As per the measuring methods tools may be classified into following types.
(i) Direct measurement tools
(a) Scale
(b) Vernier caliper
(c) Micrometer
(d) Feeler gauge
(e) Screw pitch gauge
(ii) Indirect measurement tools
(a) Calipers - These are indirect measuring tools used to measure or transfer liner and radial dimension for ex-length, width, height & diameter etc. calipers may be further classified as outside caliper (used for outside measurement) Inside caliper (use for inside Measurement) Odd leg caliper (used for making center of circular object) and driver.
(b) Try square: It may define as a measuring and marking tools for 90 angles. It’s generally made of hardened hand tempered low/high carbon steel.
(3) Marking Tools
Marking is necessary to achieve desired dimension before doing any operation its works as a basic reference during various operations with job. The marking tools are-
(a) Scriber - It is made up of hardened and tempered carbon steel.
Tip of scriber is grinded at 12 to 15 degrees and is generally available in 125 mm to 250 mm it is used for temporary marking .scriber are of two types single ended & double ended
(b) Punch- It is used for permanent marking and it is made up of hardened and tempered high carbon steel. It is specified by it is length and diameter of center punch .They may be further classified as center punch (90 angle) Dot punch (60 angle) Prick punch (30 angle).
(4) Cutting Tools:
(a) Chisel - It is used for cutting surplus material from any object which is generally difficult by hack sawing. It is made by low carbon and high carbon steel depending upon material of job. It is specified by it is width of cutting edge and total length. They are classified into two types- cold chisel and hot chisel.
(b) Hacksaw frame - It is made up of case hardened mild steel in “c” shape having a wooden handle and a wing nut used for tightening the blade. It is used for mounting hacksaw. The process of cutting by it is called hacksaw. They are classified into three type adjustable frame, fixed frame and deep cutting frame.
(c) Blade - It is metal strip having two holes’ end and cutting teeth at on e side in length. It is used to cut any material after fixing in hacksaw frame it is high carbon steel , high speed steel and low carbon steel It is hardened and tempered .
(5) Finishing Tools -
(a) Scraper - It is to remove high spot on the finished surface. It is made up of hardened and tempered tool steel. It may be classified in three types as per their shape as flat scraper, half round scraper & triangular scraper.
(b) File- It is fine cutting tool having number of cutting teeth on it is face and it is used for finishing purpose. Process of metal removing by this tool is called filling. It is made up high carbon steel and cast steel. Except of tang all body is made of hardened and tempered. Files are classified according to their shape, cut & grade as given under
According to shape - Flat file, half round file, triangular file, knife edge file, square file, diamond file,
According to cut - Single cut, double cut, rasp cut.
According to grade - Rough file (8 TPC), basted file (12TPC) second cut (16TPC) smooth file (20TPC) dead smooth file (40 TPC).
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