Fundamentals of Workshop Technology and Machine Tools

Cutting processes are those in which a piece of sheet metal is separated by applying a great enough force to caused the material to fail. The most common cutting processes are performed by applying a shearing force, and are therefore sometimes referred to as shearing processes.

Cutting tools include all of the consumable tooling involved in milling, drilling, turning and other lathe and CNC machining center operations.

Single-point tools are used in turning, shaping, planing and similar operations, and remove material by means of one cutting edge. This lecture discusses the nomenclature of the same.

Tool signature is the numerical code that describes all the key angles of a given cutting tool.

The mechanism of metal cutting can be explained in a single sentence - "A wedge-shaped tool with a straight cutting edge is made to move relative to the workpiece and a layer of metal called chip is removed."

Chips formation is part of machining process. It is formed during cutting of workpiece by some mechanical means. The chips depend on the material of work piece,tool and cutting condition. There are mainly three chips types - Continuous,Discontinuous and Continuous with Built Up Edge.

Cutting fluids are used in metal machining for a variety of reasons such as improving tool life, reducing workpiece thermal deformation, improving surface finish and flushing away chips from the cutting zone. It also helps in shaping and cutting of metals.

In this lecture, We will discuss about various types of Lathe machines in detail. As such ::

1. Bench Lathe.

2. Speed Lathes.

3. Engine Lathe.

4. Tool Room Lathe.

5. Capstan and Turret Lathe.

6. Automatic Lathe.

7. Special Purpose Lathes.

The main parts of the lathe are the bed, headstock, quick changing gear box, carriage and tailstock. Some of the most prominent parts of Lathe are discussed in this lecture.

1. Bed: The bed is a heavy, rugged casting in which are mounted the working parts of the lathe. It carries the headstock and tail stock for supporting the workpiece and provides a base for the movement of carriage assembly which carries the tool.

2. Legs: The legs carry the entire load of machine and are firmly secured to floor by foundation bolts.

3. Headstock: The headstock is clamped on the left hand side of the bed and it serves as housing for the driving pulleys, back gears, headstock spindle, live centre and the feed reverse gear. The headstock spindle is a hollow cylindrical shaft that provides a drive from the motor to work holding devices.

4. Gear Box: The quick-change gear-box is placed below the headstock and contains a number of different sized gears.

5. Carriage: The carriage is located between the headstock and tailstock and serves the purpose of supporting, guiding and feeding the tool against the job during operation. The main parts of carriage are:

a). The saddle is an H-shaped casting mounted on the top of lathe ways. It provides support to cross-slide, compound rest and tool post.

b). The cross slide is mounted on the top of saddle, and it provides a mounted or automatic cross movement for the cutting tool.

c). The compound rest is fitted on the top of cross slide and is used to support the tool post and the cutting tool.

d). The tool post is mounted on the compound rest, and it rigidly clamps the cutting tool or tool holder at the proper height relative to the work centre line.

e). The apron is fastened to the saddle and it houses the gears, clutches and levers required to move the carriage or cross slide. The engagement of split nut lever and the automatic feed lever at the same time is prevented she carriage along the lathe bed.

6. Tailstock: The tailstock is a movable casting located opposite the headstock on the ways of the bed. The tailstock can slide along the bed to accommodate different lengths of workpiece between the centers. A tailstock clamp is provided to lock the tailstock at any desired position. The tailstock spindle has an internal taper to hold the dead centre and the tapered shank tools such as reamers and drills.

There are many lathe accessories provided by the lathe manufacturer along with the lathe, which support the lathe operations. The important lathe accessories include centers, catch plates and carriers, chucks, collets, face plates, angle plates, mandrels, and rests. These are used either for holding and supporting the work or for holding the tool. Attachments are additional equipment provided by the lathe manufacturer along with the lathe, which can be used for specific operations.

The lathe attachment include stops, ball turning rests, thread chasing dials, milling attachment, grinding attachment, gear cutting attachment, turret attachment and crank pin turning attachments and taper turning attachment.

Specification of a Lathe:

1. Swing- the largest work diameter that can be swung for the lathe bed.

2. The distance between the headstock and tailstock center.

3. Length of the bed in a meter.

4. The pitch of the lead screw.

A lathe is a machine tool that rotates a workpiece about an axis of rotation to perform various operations such as cutting, sanding, knurling, drilling, deformation, facing, and turning, with tools that are applied to the workpiece to create an object with symmetry about that axis.

When the diameter of a piece changes uniformly from one end to the other, the piece is said to be tapered. Taper turning as a machining operation is the gradual reduction in diameter from one part of a cylindrical workpiece to another part. Tapers can be either external or internal.

Thread cutting on the lathe is a process that produces a helical ridge of uniform section on the workpiece. This is performed by taking successive cuts with a threading toolbit the same shape as the thread form required.

Cutting speed is defined as the speed (usually in feet per minute) of a tool when it is cutting the work. ... Feed rate is defined as tool's distance travelled during one spindle revolution.Feed rate and cutting speed determine the rate of material removal, power requirements, and surface finish.

The basic parts of a drilling machine are a base, column, drill head and spindle. The base made of cast iron may rest on a bench, pedestal or floor depending upon the design. Larger and heavy duty machines are grounded on the floor. The column is mounted vertically upon the base.

Types of Drilling Machine

• Portable Drilling Machines.

• Sensitive Drilling Machines.

• Upright Drilling Machines.

• Radial Drilling Machines.

• Gang Drilling Machines.

• Multiple Spindle Drilling Machines.

• Automatic Drilling Machines.

• Deep Hole Drilling Machines.

A drill is one of the handiest additions to the home toolbox and is essential in just about any project, whether it's a quick decor DIY, a major room upgrade or building addition. But a good drill is useless without the correct drill bits for the job.

Geometrically, the twist drill is one of the most complex metal cutting tools in use. It's designed with a cone-like internal structure – narrow at the top of the web with a gradually increasing thickness to the shank. This structure provides added strength and rigidity.

The drilling process, or complete operation, involves selecting the proper twist drill or cutter for the job, properly installing the drill into the machine spindle, setting the speed and feed, starting the hole on center, and drilling the hole to specifications within the prescribed tolerance.

Drilling machines are specified according to their type. A portable drilling machine is specified by the maximum diameter of the drill that it can handle. The size of the sensitive and upright drilling machines are specified by the size of the largest workpiece that can be centered under the spindle.

Cutting speed is defined as the speed (usually in feet per minute) of a tool when it is cutting the work. ... Feed rate is defined as tool's distance traveled during one spindle revolution.Feed rate and cutting speed determine the rate of material removal, power requirements, and surface finish.

A shaper is a type of machine tool that uses linear relative motion between the workpiece and a single-point cutting tool to machine a linear tool-path. The ram is typically actuated by a mechanical crank inside the column, though hydraulically actuated shapers are increasingly used.

In this short video lecture, Various types of shapers are discussed.

Shaper Parts:

• Base

• Column

• Cross-rail

• Workbench Table

• Ram

• Tool Head

In a standard shaper, cutting of material takes place during the forward stroke of the ram and the return stroke remains idle. The return is governed by a quick return mechanism. The depth of the cut increments by moving the workpiece, and the workpiece is fed by a pawl and ratchet mechanism.

There are 4-types of operations performed in a shaper machine, and those are: Horizontal cutting. Vertical cutting. Inclined cutting. Irregular cutting.

In this lecture,We will discuss about various types of Planer.

The working principle of the planer machine is the same as the shaper machine which is a Quick return motion mechanism. While the workpiece moving forward the forward strokes complete and while it moving back the return stroke complete. In a forward stroke, the material is cut and in backward no material is cut.

A Shaper is traditionally a small machine and preferred for smaller jobs. In a planer machine, the tool is stationary and work piece travels back and forth under the tool. In a shaper, machine work is held stationary and the cutting tool on the ram is moved back and forth across the work.

A Slotter machine consists of these following parts:

• Base.

• Column.

• Saddle.

• Cross-slide.

• Rotating or Circular table.

• Ram and tool head.

• Ram drive.

• Feed drive.

Slotting operation is a machining process whereby a work piece is held on the machine table, which is then advanced into the path of a reciprocating ram, upon which is mounted a single-point cutting tool.

Working Principle: The workpiece is holding on the worktable of the machine. The table movement controls the feed of workpiece against the rotating cutter. The cutter is mounted on a spindle or arbor and revolves at high speed. Except for rotation the cutter has no other motion.

There are two types of milling methods - UP Milling & DOWN Milling. In up milling, cutter rotates against the direction of table feed. In down milling, cutter rotates along the direction of table feed. Chip load on teeth (or uncut chip thickness) increases gradually from zero at the point of engagement to maximum at the point of disengagement.

Milling cutters are cutting tools typically used in milling machines or machining centres to perform milling operations. They remove material by their movement within the machine or directly from the cutter's shape.

Milling is the process of machining using rotary cutters to remove material by advancing a cutter into a work piece. ... Milling covers a wide variety of different operations and machines, on scales from small individual parts to large, heavy-duty gang milling operations.

Milling machines are very versatile. They are usually used to machine flat surfaces, but can also produce irregular surfaces. They can also be used to drill, bore, cut gears, and produce slots. The type of milling machine most commonly found in student shops is a vertical spindle machine with a swiveling head.

Indexing is the process of evenly dividing the circumference of a circular work piece into equally spaced divisions, such as in cutting gear teeth, cutting splines, milling grooves in reamers and taps, and spacing holes on a circle.

In this lecture we will discuss about various milling operations. This is the last lecture of this course.I hope you have enjoyed the ride. Feel free to contact me via Q/A regarding any doubts or queries you have. All the contents of the course is attached herewith. Also do remember to collect your completion certificate.

All the very BEST !!

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So this here is the last lecture of the course. I hope you understood everything. The complete contents are attached herewith.

All the very BEST !!