Metal Cutting: The Complete Guide

You cannot fabricate sheet metal without a metal cutting process.

This guide will teach you the best practices during the metal cutting process.

Whether you want to learn about techniques, methods, or applications – you will find all information right here.

What Is Metal Cutting?

It is the process of removing unwanted or excess material from a metal workpiece using a cutting tool. The process is available in different methods, and the specific one often depends on the desired ultimate result.

Metal Cutting Safety Precaution

Avoid Loose-fitted Attire
Avoid Loose-fitted Attire

Metal cutting sometimes entails using machines; thus, wearing loose clothing may get caught in the equipment and cause injuries.

Wear Eye Protection
Wear Eye Protection

Safety glasses, a face shield, or goggles are fundamental in preventing common work-related eye injuries.

Keep Cutter Deep In The Cut
Keep Cutter Deep In The Cut

Maintain the cutting tool deep into the cut as you move along and avoid creating burrs along the cut line.

Work With Sufficient Light
Work With Sufficient Light

Where possible, use natural or artificial light since most metals shine and may be challenging to see clearly under some lighting conditions.

Grip Workpiece Properly
Grip Workpiece Properly

Using a properly mounted vice is advisable to grip the piece while cutting it.

Inspect Safeguarding
Inspect Safeguarding

Ensure you inspect the safeguarding before using the machine to guarantee safety when using the equipment.

Maintain Tools & Machines
Maintain Tools & Machines

Maintaining all the cutting tools and equipment is fundamental to prevent failure likely to cause bodily harm during use.

Don’t Run Fingers Along Raw Edges
Don’t Run Fingers Along Raw Edges

Most newly cut edges tend to be sharp, and running fingers along them might cause severe cuts.

Metal Cutting Applications

They are as follows;

  • Building and construction of residential, commercial, and industrial structures.
  • Automotive industry; cutting body parts for different vehicles.
  • Metal parts assembly for numerous components to form functional units.
  • Aviation industry cuts and sizes a wide range of interior and exterior trims of aircraft.
  • Heavy machinery parts such as engine cases are also cut before assembling.
Metal Cutting Applications
Critical Conditions For Metal Cutting Process

Critical Conditions For Metal Cutting Process

They are as follows;

Cutting Speed – The relative primary motion of the cutting tool is a significant determinant of successful metal cutting.

Cutting Tool Condition – Often, tools or equipment with a sharper cutting edge tends to be more precise and efficient than a blunt one.

Relative Motion Between Cutting Tool And Workpiece – How you maneuver the cutting tool within the workpiece also defines the general efficiency of the process.

Cutting Tool Strength – The cutting tool should always be stronger than the workpiece.

Cutting Feed – Subsequent cutting needs are also necessary to determine the efficiency of the metal cutting process.

Metal Cutting History

The actual process began in Egypt, where a bowstring, a rotating device, was used to drill holes in stones. But around mid-19th Century, the scientific advancements in metal cutting began, and the first attempts to explain chip formation started between 1870-1873. In 1981, Mallock highlighted the significance of shearing and friction in the work tool interface.

By 1883, the metal cutting process had advanced, and several interventions had been put in place, such as observing the effects of cutting lubricants. However, in Mid-20th century, various cutting tools and advanced equipment were invented to enhance the overall process efficiency and reliability.

Metal Cutting History
Orthogonal Metal Cutting Process

Orthogonal Metal Cutting Process

It is a metal cutting technique with a cutting edge perpendicular to the feed direction. As such, the chip or unwanted workpiece material flow in a direction normal to the tool’s cutting edge. Simply put, the cutting tool is presented to the workpiece so that the cutting edge becomes normal to tool feed direction.

Thus, the radial force is zero and entails only two force components, simplifying the cutting motion analysis. Using a perfectly sharp cutting tool cuts the metal on rack surface. However, in many instances, the tool has a shorter cutting life in orthogonal cutting process.

Oblique Metal Cutting Process

It is a type of metal cutting process where the cutting edge is inclined at an acute angle to the direction of the feed. Hence, it enables the chip to flow sideways in a long curl in a direction at a normal angle to the tool cutting edge.

The cutting analysis includes three mutually perpendicular components of a force and is usually challenging to analyze. Moreover, the tool has a higher cutting life and produces a better surface finish than orthogonal cutting. Cuttings in oblique metal cutting may or may not necessarily be longer than the edge cut.

blique Metal Cutting Process
Sawing Metal

Sawing Metal

This metal cutting process is used for cutting the right-sized workpiece from a relatively sizeable raw material stock. Often, different saws are used in this process depending on the desired cuts and nature of material. Hacksaws are used to cut the metal in a reciprocating motion.

Circular saws are available in a shape of a circular disc, and it rotates continuously as it cuts the workpiece. Bandsaws, on the other hand, is also relatively similar to circular saws and also rotate continuously. Sawing metal gives efficient results and, in many instances, provides relative accuracy.

Shaping Metal

This process uses a single-point tool usually moved horizontally along a slide in a reciprocating motion. Ideally, it comes in handy in creating a planar surface, commonly for preparing rectangular blocks likely to be used later as workpieces for machining.

Shaping metal through cutting ensures it attains the necessary dimension, which is fundamental in attaining desired results in a specific application. Moreover, it guarantees high precision, thus ideal in applications where accuracy is a primary concern.

Shaping Metal
Broaching Metal

Broaching Metal

It is a metal cutting process that uses a toothed tool known as a broach to remove unwanted material from a workpiece. This process can produce a high volume of complex geometry parts, specifically in applications where shapes are needed for machining.

Ordinarily, the broach tool used in this method contains a series of cutting teeth along the tool axis. Each tooth cuts a tiny chip as you pull the broaching tool with force along the part of workpiece you are cutting. The first few teeth sets to engage the part removes most material, and the last few give a finishing cut with a small volume of material removal.

Turning Metal

Turning is a metalworking process involves a disc or tube rotating at an extremely high speed to enable metal formation in desired configuration. Primarily, it entails applying a sharp point of a cutting tool to a metal surface, rapidly rotating it.

As such, it removes the top metal layer to a specific pre-determined size. You can use a lathe or hand to turn metal, but it requires a high level of expertise to attain the best results. Moreover, the cutter used in this process is usually a single-point cutting tool connected to the equipment.

Turning Metal
Drilling Metal

Drilling Metal

It is a metal fabrication technique that involves creating holes on exact specifications in a metal surface or component. The process applies pressure and rotates on top of metal surface or component to create the hole. Ideally, drill bit tool used in this process has a complex geometry with straight cutting teeth at the bottom and curved cutting teeth along a cylindrical surface.

The helical teeth create grooves called flutes and are essential in pushing chips out from the hole being drilled. This process efficiently creates holes for different purposes on a metal component or surface.

Reaming Metal

It is a process used for high precision enlarging a previously created hole on a metal surface or component. The technique uses a rotary tool known as a reamer to enlarge a workpiece accurately.

Primarily, reaming metal requires an existing hole as a starting point since a reamer can hardly create holes from a plain metal surface. As such, drilling is often required before reaming to guarantee efficiency and accuracy in expanding the created holes. The diameter of expanded holes varies depending on the type of application, but you can always use different reamer sizes based on your needs.

Reaming Metal
Tapping Metal

Tapping Metal

This metal fabricating technique uses a tapping tool to create material in an extruded or pre-punched hole to form threads. Often, the threads are helpful for engagement of self-tapping screws mostly needed for connecting a single piece of metal to another.

Usually, the tapping tool uses each machine stroke to produce an exact thread in specific programmed locations. The tool is thus engaged with each stroke as the tap rotates to form the material and create the pitch of thread required. Tapping tool has an in-built fluid injection mechanism synchronized with machine’s stroke to reduce tool wear.

Honing Metal

It is a process of attaining the final sizing and creating desired surface finish on cylinder bores or tubing interior. This technique is accomplished by expanding abrasive stones with suitable grade and grit against work surface.

Hence, stones are rotated and reciprocated in the metal part under controlled pressure with a hone abrasive. A combination of rotation and reciprocation yields a cross-hatch pattern in the surface of component being honed. Horning metal is a vital operation since it ensures you attain extremely accurate roundness, straightness, and size of the specific cylindrical surface.

Honing Metal
Lapping Metal

Lapping Metal

It is a specialized process designed to make metal parts surfaces as close to homogeneously flat as possible. You can also use this technique to polish metallic surfaces to a fine finish and attain a mirror finish with specific metals. It achieves a flatness tolerance of 0.0005 to 0.00002 inches.

Besides, it is easier to finely tune the pressure on parts and process duration to accommodate part material and the desired final finish. You can lap metal parts and components within 10 to 20 millionths of an inch of flatness under perfect conditions.

Boring Metal

It is the process of using a single-point cutting tool to enlarge an already existing drilled hole on a metal surface or component. This process is essential in attaining greater precision of hole diameter and can be used for cutting tapered holes.

You can view it as the internal-diameter counterpart to tuning that cuts external diameters. Boring is available in numerous types, but the common ones include line-boring and back-boring. The main tools in boring metal are solid boring bars, rough boring heads, twin cutter boring heads, digital boring heads, and damping bars.

Boring Metal
Boring Metal

Milling Metal

It is a material removal process used for creating a wide range of features on a part by cutting away unwanted or excess chips from a workpiece. Milling metal is mainly designed for creating holes that need flexibility when used in different applications. However, the amount of chips the mill can remove from the workpiece is dependent on mill’s diameter and material’s hardness.

Ideally, the maximum thickness which can be removed from the workpiece at a go is the diameter of the milling tool. The mill goes through the workpiece severally if the workpiece is thicker than what the milling tool can remove.

Grinding Metal

This is a cutting process used in metal fabrication designed to remove rough edge components by deburring, smoothening out welds, and creating sharp edges. It is always done using a grinding machine, but in larger operations, the process uses dedicated finishing machines.

Grinding wheel is mainly used in this process hence often manufactured with precision-shaped grains of conventional grains. Thus, it remains the primary element in determining the efficiency of this process from the perspective of abrasive grains the wheels employ.

Grinding Metal
Cutting Metal Through Welding

Cutting Metal Through Welding

In this case, welding involves application of high heat to the metal surface, which brings it up to an exceptionally high temperature. The temperature softens the metal and, consequently, allows it to break a long, precise line.

This process forms an arc between the workpiece and an electrode manually guided along the joint. The purpose of the electrode is to convey the current between the tip and the workpiece. As such, the arc produces a relatively high temperature, which melts the base material and electrode to smoothen and cut the metal.

Flame Cutting Metal

It entails oxygen cutting where the appropriate workpiece part to be cut is raised to an ignition temperature by an oxy-fuel gas flame. This process is used for separating and shaping a wide range of metal components. Ideally, it is conducted using a torch where oxygen and fuel gas are passed.

In essence, the torch nozzle has outer rings of jets used in preheating the metal workpiece. A different oxygen stream is directed to the specific section to be cut from a central jet in the torch nozzle. Consequently, rapid metal workpiece oxidation occurs, and the gas pressure separates the material.

Flame Cutting Metal
Water Jet Cutting Metal

Water Jet Cutting Metal

It is a metal cutting process that uses immense pressure jets of water offered by pressurized pumps. These pumps deliver a stream of water at supersonic pressure to cut and shape metals in different sizes. Water jet cutting is pressurized to about 392Mpa and directed using a small precision nozzle.

Hence, it becomes easier to manipulate the nozzle to cut different metal sizes into various shapes. This process is available in two forms; abrasive and pure water jet cutting, each designed for specific types of metal surfaces.

Plasma Cutting Metal

It is a cutting process where a jet ionized gas at extremely high temperatures melts and expels material from the cut. Primarily, an electric arc is struck between workpiece and electrode. The electrode is recessed in water or air-cooled gas nozzle that strains the arc and causes narrow, high velocity, and high-temperature plasma jet formation.

Once the plasma jet hits the workpiece, recombination takes place; hence gas reverts to its ordinary setting. This technique is relatively new in metal fabrication but is commonly used to form or cut different types of metallic materials.

Plasma Cutting Metal
Laser Cutting Metal

Laser Cutting Metal

It refers to a technology that utilizes a laser to vaporize metal surfaces leading to a cut edge. This process guarantees utmost precision, control, and speed. In laser cutting metal process, a highly concentrated light beam at high temperature is utilized in cutting a component in specific sizes and shapes.

The precision levels of laser cutting metal arise from a computer system used in tandem to manage the process. Such high accuracy levels make laser cutting metal ideal in fabrication, where adherence to plans is of utmost significance. Besides, it is quite expensive and one of the most intensive processes.

Parameters Influencing Metal Cutting

Parameters Influencing Metal Cutting
Parameters Influencing Metal Cutting

The primary factors that determine metal cutting are as follows;

Machinability

Different metal materials have unique properties that determine their machinability. Hence, it is important to establish the machinability of the specific metal you are cutting. Machinability determines the power, force, tool life, and ultimate surface finish.

Temperature

It is imperative to determine the level of temperatures used in tandem with material property. Besides, it should never be too high since it could lead to thermal damage to workpiece, tool wear, and dimensional accuracy.

Cutting Fluid

This element reduces friction during metal cutting to ensure a smooth and seamless process. But you must ensure you are using the recommended one depending on the method you are using.

 Tool Geometry

Ultimately, the tool geometry determines the cutting force, shape, and dimension of the desired result. Moreover, it influences the chip flow direction and type of chips.

Tool Wear

The condition of cutting tool plays a fundamental role in determining the overall efficiency of metal cutting process. It determines temperature rise, power and force requirement, dimensional accuracy, and surface finish.

Types Of Chips In Metal Cutting Process

Continuous Chip
Continuous Chip

This is a relatively large plastic deformation of metal workpiece occurring ahead of tool cutting edge. It involves compressing metal workpieces and sliding over tool force in form of a long continuous chip.

Discontinuous Chip
Discontinuous Chip

It is a form of segmented chip produced in the form of tiny pieces. Often, these chips are produced when cutting a wide range of brittle metals.

ontinuous Chip With Built-Up Edge
Continuous Chip With Built-Up Edge

This refers to small metal particles sticking to the cutting tool and machined surfaces due to high temperature, frictional resistance, and pressure during machining. As such, chips build up and break down, then decreases, and the cycle repeats.

Metal Cutting Tools

Oxy-Acetylene Torch
Oxy-Acetylene Torch

It mixes oxygen with acetylene from tanks and allows high-temperature flame to cut metal pieces upon lighting its nozzle.

Tin Snip
Tin Snip

This handheld tool cuts metal in straight, curved, and circles.

Metal Air Shears
Metal Air Shears

It is a power tool designed for cutting relatively hard metal surfaces and mostly suitable for cutting in bulk.

Angle Grinder
Angle Grinder

This tool uses a cutting wheel to cut-off metals into different pieces, sizes, and shapes.

Cold Saw
Cold Saw

It uses a coolant feature to reduce friction between workpiece and cutting blade while offering clean and precise cuts.

Metal Cutting Circular Saw
Metal Cutting Circular Saw

This tool is more or less similar to cold saw and allows you to carry-out spark-free cuts on numerous types of metal materials.

Sheet Metal Nibbler
Sheet Metal Nibbler

As the name indicates, this is a power tool designed for making cuts on metal sheets.

Reciprocating Saw
Reciprocating Saw

It is an aggressive power tool with reciprocating metal blades offering accuracy, speed, and multiple blades to choose from.

Hole Saw
Hole Saw

It is primarily a drill bit attached to a drill press for cutting circles.

Plasma Cutter
Plasma Cutter

This is equipment designed to cut through electrically conductive materials by means of an accelerated hot plasma jet.

Laser Cutter
Laser Cutter

It is a prototyping and manufacturing tool that uses a thin, focused laser beam to cut through different materials.

Metal Cutting Terminologies

Flank Surface
Flank Surface

It refers to the surface between cutting tool bottom and workpiece.

Rack Surface
Rack Surface

It is the area between cutting tool top surface and chip.

Rack Angle
Rack Angle

This is the angle between the ordinary metal workpiece and rack surface.

Relief Angle
Relief Angle

It is the angle between horizontal machined surface and flank surface.

Primary Deformation Zone
Primary Deformation Zone

This is the zone between cutting tool tip and shear plane AB.

Secondary Deformation Zone
Secondary Deformation Zone

It is the area between chip and tool rack surface.

Tertiary Deformation Zone
Tertiary Deformation Zone

This is the zone between workpiece machined surface and tool flank surface.

People Also Ask:

How Can You Cut Thick Metals?
  • Using rotary tools such as drills
  • Using power tools like angle grinder, cold saw, metal air shears, and metal nibblers among others.
  • Using computerized tools like laser cutter
  • Using improved technology like water jet cutter, plasma cutter, and oxy-acetylene torch.
What Is Metal Cutting Tool?

It is a hardened metal tool used for cutting, shaping, and removing excess or unwanted material from a workpiece by machining.

What Is Metal Cutting Machine?

It refers to a type of machine tool used for fabricating parts by removing material from the metal surface or component.

How Can You Cut Thin Metal?
  • By using a tin snip to cut through the thin metal sheet.
  • Using a Dremel blade when you are making detailed cuts in thin metal
  • Using a nibbler
  • Using an electric metal shear in applications where speed and high volume are needed.
Can Multi Tools Cut Metals?

Yes.

However, an oscillating power tool is the best option to choose for cutting metals.

Related Resources:

Plasma Cutting

Water Jet Cutting

Sheet Metal Laser Cutting

Sheet Metal Shearing

Cutting Sheet Metal

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