Fundamentals of Machining & Machining Operations

Flashcards covering fundamentals of machining, chip formation, tool geometry, lathe and drilling operations, and machine specifications.

Mechanics of Chip Formation

The process where a wedge-shaped tool moves relative to a work piece, exerting pressure that results in compression and shear-type deformation, eventually separating material when the compression limit is exceeded.

Shear plane

The plane along which material ahead of the tool is sheared continuously during the machining process.

Shank

The main body of the tool at one end of which the cutting portion is formed.

Flank

The surface (or surfaces) below and adjacent to the cutting edge of a single point cutting tool.

Face

The surface of the tool on which the chip slides.

Heel

The intersection of the flank and the base of the tool.

Nose

The point where the side cutting edge and the end cutting edge intersect.

Neck

The portion of the tool which is reduced in section to form necessary cutting edges and angles.

Cutting edge

The edge on the face of the tool which removes the material from the work piece.

Side cutting edge angle

Also known as the 'lead angle,' it is the angle between the side cutting edge and the side of the tool shank, typically ranging from $15^{\circ}$ to $30^{\circ}$.

End cutting edge angle

The angle between the end cutting edge and a line normal to the tool shank, with values typically between $8^{\circ}$ to $15^{\circ}$.

Side relief angle

The angle between the portion of the side flank immediately below the side cutting edge and a line perpendicular to the base of the tool.

End relief angle

The angle between the portion of the end flank immediately below the end cutting edge and a line perpendicular to the base of the tool, ranging from $5^{\circ}$ to $15^{\circ}$.

Back rake angle

The angle between the face of the tool and a line parallel to the base of the tool, measured in a plane perpendicular through the side cutting edge.

Side rake angle

The angle between the tool face and a line parallel to the base of the tool, measured in a plane perpendicular to the base.

Tool signature

A system for designating the principal angles and nose radius of a single point cutting tool, typically following the sequence: Back rake, Side rake, End relief, Side relief, End cutting edge, Side cutting edge, and Nose radius.

Continuous chip

Ribbon-like chips produced while machining ductile materials; they provide a good surface finish but can be difficult to handle and may injure the operator.

Discontinuous chip

Chips produced in segments while cutting brittle materials, leading to unstable cutting but better handling.

Built-up chip

Occurs when work material gets welded to the cutting edge due to high temperature and pressure, forming a built-up edge (BUE) that protects the tool edge but causes rough surface finish.

Cutting Speed

The relative surface speed between the tool and the job, expressed in $m/min$, or the length of work material passing the cutting edge per unit time.

Feed

The distance the tool advances for each revolution of the work, expressed in $mm/rev$.

Depth of cut (Lathe)

The thickness of the layer of metal removed in one cut, measured perpendicular to the machined surface, calculated as $\frac{D_1 - D_2}{2}$.

Machining time

The calculation of time taken for a complete cut, expressed as $\frac{L}{S \times N}$, where $L$ is length, $S$ is feed, and $N$ is RPM.

Bed

The heavy rigid casting, usually made of grey Cast iron, that serves as the foundation of the lathe to support all other parts.

Head stock

Permanently fastened to the left end of the bed, it supports the spindle and driving arrangement, and may be hollow to allow long bars to pass through.

Tail stock

Situated at the right hand end of the bed, it is used to support the right side of the work and hold tools like drills and reamers.

Carriage

The assembly that controls and supports the cutting tool, consisting of the saddle, cross slide, compound rest, tool post, and apron.

Saddle

An H-shaped casting fitted over the bed that move along the guide ways and carries the cross slide and tool post.

Cross slide

Mounted on the saddle, it provides cutting tool motion perpendicular to the center line of the lathe.

Compound rest

Mounted on the cross slide and marked in degrees, it is used during taper turning to set the tool for angular cuts.

Apron

Attached to the saddle and hanging in front of the bed, it contains gears and levers for moving the carriage with the lead screw.

Chuck

A device used for holding and rotating a work piece in a lathe, attached to the spindle by bolts.

Steady Rest

Also called a centre rest, it is a stationary attachment with three adjustable jaws used to support long workpieces and prevent deflection or bending.

Facing

A lathe operation to produce a flat surface at the ends of a work piece by feeding the tool perpendicular to the axis of rotation.

Taper

A uniform increase or decrease in diameter of a piece of work measured along its length.

Taper turning

A method to produce a conical surface by feeding the tool at an angle to the axis of rotation of the work piece.

Knurling

The operation of embossing a diamond-shaped pattern on the surface of a workpiece to provide an effective gripping surface.

Threading

An operation of cutting helical grooves on the external cylindrical surface of a work piece.

Reaming

An operation using a multi-tooth cutter to finish an existing hole smoothly and accurately to a specific size.

Boring

An operation of enlarging an existing hole using a single point cutting tool.

Counter Boring

An operation of enlarging a drilled hole partially up to a specific length to accommodate socket head screws or bolts.

Spot Facing

The operation of smoothing and squaring the surface around a hole to provide a seat for a nut or screw head.

Counter Sinking

An operation of forming a conical shape at the end of a drilled hole, typically at angles of $60^{\circ}$, $82^{\circ}$, or $90^{\circ}$.

Cutting speed (Drilling)

The peripheral speed of a point on the surface of the drill in contact with the work piece, expressed in $m/min$.

Depth of cut (Drilling)

Defined as the distance from the machined surface to the drill axis.