INTRODUCTION TO METAL CUTTING:
Metal cutting is the process of producing a job by removing a layer of unwanted material from a
given workpiece. Fig. shows the schematics of a typical metal cutting process in which a wedge
shaped, sharp edged tool is set to a certain depth of cut and moves relative to the workpiece.
Under the action of force, pressure is exerted on the workpiece metal causing its compression
near the tip of the tool. The metal undergoes shear type deformation and a piece or layer of
metal gets repeated in the form of a chip.
If the tool is continued to move relative to workpiece, there is continuous shearing of the metal
ahead of the tool. The shear occurs along a plane called the shear plane.
All machining processes involve the formation of chips; this occurs by deforming the work
material on the surface of job with the help of a cutting tool. Depending upon the tool
geometry, cutting conditions and work material, chips are produced in different shapes and
sizes. The type of chip formed provides information about the deformation suffered by the
work material and the surface quality produced during cutting.
Types of Chips:
Continuous chips: While machining ductile materials, large plastic deformation of the work
material occurs ahead of the cutting edge of the tool. The metal of the workpiece is
compressed and slides over the tool face in the form of a long continuous chip
Discontinuous (segmented) chips: A discontinuous chip is a segmented chip produced in the
form of small pieces. The discontinuous chips are produced when cutting brittle materials like
cast iron, bronze and brass. The working on ductile materials under poor cutting condition may
also sometimes lead to the formation of discontinuous chips.
Continuous chips with built-up-edge: The term built-up-edge refers to the small metal particles
that stick to the cutting tool and the machined surfaces as result of high temperature, high
pressure and high frictional resistance during machining. The building up and breaking down of
the built-up-edge is periodic; its size first increases, then decreases and again increases-the
cycle gets repeated rapidly.
KINDS OF CUTTING TOOLS USED IN MACHINING
From the guts of a car to the components of an airplane, machining cutting tools craft hunks of
metal into reliable precision parts. Machining cutting tools range from rough cutting
equipment, like chop saw or grinder, to programmable, production oriented machines, like the
metal mill. Learn about the different types of cutting tools used by machinists so you can deck
out your shop with basic tools for hobby pieces or heavy equipment for industrial-level
projects.
Lathe
If you have ever wondered how to turn stairway posts,
a lathe is the answer. The lathe of a machinist
functions like a wood-burning table, but gives the
power and precision for milling metal. Mount the
material at each end to the lathe, then turn the lathe
and press the cutting edges against the material as it
rotates. You can also manually press cutting edges
against the material, or program and operate the cuts
via computer input.
Drill Press
The drill press bores precision holes,
reams openings and cuts threads.
The drill press features an arm that
suspends a drill over a stationary
base. Put the material at the base,
then activate the drill and lower it
through the material. Drill presser
lower on a fixed axis; they cut
precisely straight up and down.
Milling Machine
A machine otherwise known as metal mills; milling
machines refer to a variety of metal cutting and shaping
machines that can be specially built, commercially
available or proprietary. Programmable milling machines
that perform numerous cutting operations on various axes
are called CNC machines. Most milling machines feature
mobile, rotary cutting tools that pierce, cut and shape a
piece if fixed material.
GRINDER
A handheld power tool that spins abrasive or
sharpened discs to grind, shape and cut
materials. The portability of the grinder allows
it to cut and shape in areas where stationary
cutting tools cannot.
Chop Saw
The chop saw is a stationary
rough cutting tool that can be
used to cut materials to length.
A chop saw features a spinning
abrasive or sharpened blade
suspended from an arm above a
stationary base. When lowered,
the blade cuts through material
resting on the base in a
chopping motion.
WELDERS
Welding tools use ultra-hot,
concentrated flame to cut
through material. A welders
flame can melt its way through
hard and thick materials without
physical resistance. However,
this usually results in rough or
dirty edges.
Handheld Rotary Tools
The spin attachments of rotary tools, called
bits, are used for carving, cutting, reaming and
de-burring. Handheld rotary tools usually
weight less than a pound and, because their
attachments are small, can be used to complete
detail or precision work by hand.
If you have some training or experience, you
should be able to handle some cutting tools on
your own. But if you are still fairly new to this
trade, it would be best that you contact a
machining San Jose company. This way, you are
assured of quality and precise cuts for your
hobby or machine parts.
