Metal Machining: The Ultimate Guide

Metal machining is an operation where unwanted material is cut to the required ultimate shape and size by a regulated-material removal process.

In essence, this operation involves different technological methods to remove, shape, and design a metal work piece.

This article demystifies various machining techniques, how they work, benefits, and when to consider a specific one.

Moreover, you’ll understand the tips for choosing the most suitable metal machining operation solutions for your requirements.

Let’s dive right in:

How To Determine Cost Of Metal Machining

Metal machining

Various machinists consider a wide range of factors to establish the cost of the specific process.

Ordinarily, such considerations often vary from one manufacturer to another, but the common denominators among most machinists include the following;

Material Size

Metal machining is quite broad, and it implies you can use it on various metal materials.

However, since machining is a subtractive operation, it means the process uses more material than what you would have on final piece.

Hence, machinists often buy such materials in blocks and calculate the cost per block.

Material Type

You can machine a wide range of metals using various machining operations.

Aluminum, brass, stainless steel, zinc, copper, and magnesium are the common types of metals often machined.

However, all these materials have varying structural properties that determine complexity or simplicity of machining process.

As such, this significantly determines the actual cost of undertaking this process.

Machining Method

Metal machining cost also depends on the method, determining the type of machine to use.

For instance, CNC machining is quite costlier than drilling since the former entails use of highly advanced technology and equipment.

Besides, the former guarantees faster and more accurate results than the latter.

Also, the number of hours the specific operation is likely to take determines the actual price you’ll incur.

Labor

Different metal machining operations utilize or require different labor need for effective execution of the process.

Mostly, labor needs in such processes revolve around designing, programming, machine set-up, and post-processing.

In essence, the number of people you’ll require in such phases determines the overall cost of the machining process.

Auxiliary Operations

In metal machining, you may need various additional operations to enhance the efficiency of the specific parts depending on application needs.

Common additional operations include surface finishing and tooling.

Thus, the need for such auxiliary operations on your part is also a significant determinant of the actual cost.

Types Of Metal Machining Techniques

Metal machining processes are quite a number in the market.

Of course, this is imperative because it broadens the choice of an ideal method to ensure you attain the right solution.

Nonetheless, the common machining operations for metal materials include the following;

Metal Turning

Metal turning refers to a machining process, which involves removal of unwanted materials from a workpiece to create rotational parts.

Ordinarily, this operation entails cutting away the unwanted material using a turning machine, cutting tool, fixture, and workpiece.

Often, metal turning produces rotational axis-symmetric with several features like holes, tapers, contoured surfaces, and grooves.

You can also use it as a secondary process to enhance or refine features on components or parts, which were manufactured using different operations.

 Metal turning process

Benefits Of Metal Turning

Notably, metal turning is among the most basic machining operations; many machinists use it to create parts for different applications.

Thus, it means this process is quite beneficial in several ways in the machining industry, such as the following;

Affordable

Metal turning is arguably one of the most economical machining operations available.

Ideally, the process does not require complex machines or tools to execute.

Instead, it uses basic equipment and tools, which are also easy to set up.

In essence, these make metal machining quite an affordable operation to consider, especially for mass production.

Easy To Perform The Operation

You can efficiently perform metal turning with a basic skill set.

The most important element in metal turning process is ensuring you understand basic principles of the operation, equipment, and tools.

Technically, this is advantageous since it implies it reduces labor costs and other related elements.

Besides, it means you can easily create a part using this process without necessarily acquiring more knowledge.

Flexible Material Removal Rate

Metal turning makes it easy for you to determine the rate at which you want to remove the unwanted material from the workpiece.

Ideally, material removal rate in this operation can vary from very small to some significant amount.

In essence, it makes it easy for you to create a specific part based on the amount of material you decide to remove.

Easy To Obtain Close Tolerance Parts

This machining technique increases close tolerance in parts.

Essentially, this is beneficial because it means you can easily obtain accurate parts that suit specific applications.

Easy To Use A Single Tool For Multiple Operations

You can use a single tool in metal turning to carry out various operations.

Ordinarily, you do not necessarily need to use different tools for different operations in metal turning.

The most important aspect is ensuring you change the machine’s set-up to fit the requirements of the specific operation but use the same tool.

Technically, this is beneficial since it enhances convenience and reduces unnecessary tooling costs.

Easy To Obtain Desired Surface Finish

Metal turning operation makes it easy to get the ideal surface finish on your final machined product.

You can use it to prepare the surface material for the respective finishing operation.

Eco-friendly

Metal turning is an ideal environmentally friendly machining approach.

Notably, this process is a low-emission operation, which in many instances produces insignificant waste.

Besides, there are no toxic compounds involved in the operation. In other instances, you can recycle and use the materials as your blank.

Short Lead Times

It is quite a fast process making it possible to attain short lead times.

In essence, it means you can easily use metal turning to create several parts within shortest time possible.

Common Metal Turning Defects

Surface defects during metal turning

Essentially, the most common defects you are likely to encounter in metal turning operations are part dimensions inaccuracies or surface roughness.

A number of factors can be attributed to causing these defects, such as the following;

• Dull cutting tool – While using the tool, the sharp edge wears down and becomes dull, turning it relatively incapable of making precision cuts.
• Indecent cutting parameters – Some cutting parameters such as spindle speed, depth of cut, or feed rate can occasionally be high.

Such makes the workpiece surface a bit rough than expected results. Moreover, a considerable depth of cut may as well lead to tool vibration, causing imprecisions in the cut.

• Loose workpiece – If the workpiece is improperly clamped, it is likely to cause friction of turning, which may cause it to shift and change the expected results.

How Metal Turning Process Works

Metal turning process

Generally, metal turning involves removing unwanted material by rotating a workpiece across, which removes the material.

The entire process is facilitated by cutting fluids, a lathe or turning machine, a workpiece, and a fixture.

So, the workpiece is held in a specific work holding device like a chuck, and the tool is fixed in a tool post.

The tool gradually generates a surface by removing chips from a workpiece, rotating, and feeding into a cutting tool.

The chips are swept away by the rotating workpiece.

Once the chips are cut from the workpiece to the desired level, the workpiece produces cylindrical external and flat surfaces during the operation.

When To Choose Metal Turning Process

Metal turning process is an ideal choice to consider under the following circumstances;

• When producing rotational, axis-symmetric parts that typically have several features. For instance, if you want a part with holes, diameter steps, contoured surfaces, threads, grooves, and tapers among others.
• When enhancing or refining features on different parts manufactured using various processes.

Essentially, metal turning adds precision rotational features to a part with an already formed basic shape.

Different Process In Metal Turning

Metal turning is available in a wide range of processes, which include the following;

Grooving – It involves cutting grooves into the internal and external surface material of metal to a specific depth.

Drilling – This is a metalworking operation of removing material from the internal surface. It uses drill bits, which are held stationary in the lathe’s tool turret.

Boring– It is an operation, which involves enlarging an already existing hole on a workpiece using a single-point cutting tool.

Hard turning – It is more or less similar to grinding since it is often done on a workpiece once it is heat-treated.

Parting – This turning operation creates deep grooves, which remove a partially- done or completed part from its primary stock.

Threading – It involves creating screwing threads on a lathe using an ideal cutting tool.

Reaming – This is a sizing operation used for removing a small amount of material from an already drilled hole to attain accurate diameters.

Knurling – It is a metal turning operation that involves cutting serrated patterns on a part’s surface using a dedicated knurling tool.

Facing – In the context of metal turning, it entails moving the selected tool at correct angles to the workpiece’s rotation axis.

Contour turning – This operation involves cutting tool axially following the path using predetermined geometry.

Polygonal turning – It is a turning process of machining non-circular forms without interrupting workpiece’s rotation.

Spherical turning – This operation creates a ball shape on a workpiece.

Metal Drilling Process

Metal drilling machine

This operation involves using a drill bit to create a circular cross-section hole in materials.

In several instances, metal drilling is done by different drill bit designs.

However, you can also execute it using drill presses or attaching drilling tools to compatible lathes or mills.

Technically, this operation involves pressing the drill bit against workpiece and rotating it at different rates in revolutions per minute.

In turn, this forces the cutting edge against workpiece cutting off swarf from the hole as it is drilled.

How To Choose Drill Bit For Metals

Parts of drill bit

Ideally, it is imperative to find the right drill bit to enable faster and convenient boring of holes.

Some of the fundamental factors you can look into when choosing an ideal drill bit include the following;

Type Of Material Used For Making The Drill Bit

Ordinarily, the suitable drill bit material is often determined by the element of hardness.

Thus, it is recommendable to choose a drill bit designed from a harder metal, especially if you are drilling harder material substrates.

Simply put, always choose a harder drill bit than the substrate.

Type Of Drill Bit Point

Technically, the point type often used for a wide range of general-purpose applications is known as a conventional point drill bit.

Among these drill bit points, the 135° drill point angle is usually used in relatively heavy-duty applications.

It is suitable for tight tolerance applications, and the increased angle bites often bite into the material preventing the bit from straying.

Length

Intrinsically, drill bits are available in five standard length categories, which include the following;

• Jobber length– They are commonly used for general drilling purposes and have a flute length of about 9-14 drill diameter.
• Taper length – Are the ones engineered for pre-drilling pilot holes
• Extra length – Also referred to as aircraft-length drill bits are designed for drilling through an Aeroplane fuselage.
• Mechanics length – The designs of these drill bits feature shorter flute length and shorter overall length than typical jobber length drill bit. Hence, they are less susceptible to breakage and ideal for drilling harder materials.
• Screw machine length – They are the shortest of the drill bits available and have the lowest length-to-diameter ratio.

Ordinarily, the bit diameter often determines its actual length.

Type Of Surface Coating

Coated drill bit

Most drill bit manufacturers usually apply coating materials on their respective bits to enhance their overall durability.

Besides, such surface coatings often enhance the performance advantages of the drill bits under certain conditions.

The commonly used surface coatings on drill bits include the following;

• Black oxide coating – It helps in retaining lubricants often used for smoother and cooler drilling.

However, it is not necessarily ideal for non-ferrous metals such as aluminum.

• Bright finish – This generally means the drill bit does not have a surface coating. Instead, the drill bits are polished to enhance chip removal ability hence ideal for non-ferrous metals like aluminum.
• TiN coating – It is a coating that provides extra lubricity at the drill point for relatively high drilling speeds and extended tool life.
• TiAIN coating – This is the most effective drill bit coatings for applications where higher drill speeds and feed rates are required.

Hence, when selecting the ideal drill bit for your application demands, it is important to consider the specific surface coatings on the bits.

Process Of Determining Drilling Speed For Metals

Drilling speed for metals is determined by revolutions per minute (RPM).

Often, when drilling into relatively hard metal materials, it is advisable to go slower.

While the bit turns, it starts biting into the surface material.

Hence, it causes friction, heating the material and the drill bit.

You need to watch whether the material begins to show signs of discoloration or smoke.

It is likely to imply that drill bit creates excessive friction that is likely to overheat and cause warping and damaging the material.

In determining the drill speed, here are the important elements to figure out;

• Establish the material you are using
• Find the appropriate drill bit suitable for material you are drilling
• Figure out the size of the hole you want to drill in the material
• Determine if you wish to get the job done faster or preserve the drill bit’s life
• Always start on a slow RPM setting ensure you test the bit
• Pay attention to material always, especially at high speeds
• Gradually increase the RPM of the drill if the bit is cutting fine and you desire a faster pace
• Always adjust accordingly

Best Machines To Use In Metal Drilling

A suitable drilling machine increases efficiency, performance, and reliability.

Ordinarily, drilling machines are designed based on different industrial needs are often categorized as manual or automatic drills.

Nevertheless, both have different applications and can create small to bigger holes.

Hence, some of the best machines to consider in metal drilling operations include the following;

Radial Drilling Machine

It is suitable for drilling materials of different sizes that range from small to medium.

This drilling machine comprises a bigger circular base with a raised heavy round column.

Its drill head mechanism is fixed over its radial arm, which can swing 360°.

Radial drilling machine’s mechanism allows it to move throughout its arm’s length.

Multiple Spindle Drilling Machine

It comprises several spindles attached to a single motor.

Often, this drilling machine is mounted on a drill bit and used for production work.

The design of the multiple spindles allows you to adjust them for desired speeds easily.

Upright Drilling Machine

It is made of a vertical column often mounted over the base.

The design construction of this machine is sturdy and excellent for medium-sized jobs.

Gang Drilling Machine

This machine comes equipped with single spindle drilling columns placed side by side.

It is easy to alter the feed and speed of each spindle with most of the gang drilling machines.

Even so, some gang drilling machines are not necessarily adjustable because they are fixed permanently.

Step-by-step Metal Drilling Process

Metal drilling is quite a straightforward process as long as you have all the suitable materials, tools, and equipment.

However, the process may vary based on the specific drilling technique you are using.

When using a drill bit, here are the primary steps to follow;

• Get the appropriate drill bit for the task – HSS drill bits are ideal for numerous metal materials. But for tough metals such as steel, it is advisable to use carbon steel bits coated with TiN.
• Tighten loose workpiece you are drilling – Clamp the workpiece tightly to your workstation or set it in a vice. However, this process is unnecessary if you are drilling into a large and heavy object like a stud or wall.
• Mark the drilling points using a pencil – Measure the dimensions precisely, given it’s harder to patch a mistake in metal.
• Set the drill bit in place on divot – Ensure the drill is set to level to desired drill angle.
• Apply consistent pressure to drill metal – When drilling harder metals, always keep the drilling speeds relatively slow and steady. But you can apply faster drilling speeds on softer metals.
• Remove the drill bit after reaching desired depth – Let the drill bit spin until you remove it wholly from the metal.

Always ensure you wear protective gear such as eye goggles and gloves when drilling metals.

Common Metal Drilling Problems

During metal drilling, you are likely to encounter different challenges arising from various factors.

However, most of such problems are easily avoidable or easy to fix.

Some common challenges you are likely to encounter when drilling metals include the following;

• Broken drill bit

It can happen due to many reasons such as dull twist drill, using improper point, excessive speed, end of the hole, clogged flutes, cheap drill bits, etc.

• Slipping drill bit

Often caused by loose workpiece and worn out or chuck.

• Drill bit blunting faster

Mostly, this arises due to failure of coolant to reach the drill point or using insufficient coolant during drilling.

It could also be a result of too much speed, insufficient feed, and using wrong type of point.

• Breaks in the outer corners

The leading causes of this metal drilling defect are using incorrect or insufficient coolant, excessive speed, and hard spots on metal surfaces.

• Chipping on cutting edge

Excessive cutting speeds are the main cause of this particular defect.

• Wandering drill bit

Insufficient friction on work surface and using incorrect drill bits are the major causes of this problem in metal drilling.

Safety Rules When Drilling Metals

Metal drilling produces tiny, curly, and sharp chips that are somewhat hazardous, especially to your skin and eyeballs.

Therefore, it is always advisable to ensure you put on the necessary safety gear before beginning this process.

This is an important safety measure since it allows you to protect your eyes and skin from the loose metal chips produced during drilling.

Besides, it increases convenience and productivity since you are less likely to pause to deal with loose chips in your eyes.

Another critical safety measure when drilling metal is always ensuring you clamp your workpiece appropriately.

Drill bits tend to be quite powerful and continuously vibrate; hence likely to loosen the workpiece is incorrectly secured.

Besides, drill bits tend to grab metal just as they break through the material.

In some instances, the drill bit stops cold, which transfers the spinning force to the workpiece.

Thus, the workpiece must be adequately secured; it can jerk and or spin suddenly, and this could be hazardous to the operator.

Milling Metals

Metal milling process

Milling is a machining process that uses rotary cutters to remove unwanted material by advancing a cutter into a metal workpiece.

Ordinarily, this process requires a milling machine, workpiece, fixture, and cutter.

In milling, the workpiece is pre-shaped by a sharp cutting tool secured in a high-speed rotating milling machine.

This machining operation is typically used for producing parts, which are not axially symmetric and tend to have several features.

Benefits Of Metal Milling Process

Metal milling is one of the most common machining processes used for creating parts for different applications.

Some of the notable benefits this operation presents include the following;

• Guaranteed quality product

Metal milling produces identical outputs, which is vital in making bulk parts for a similar application.

• Reduced production cost

This process allows you to save money related to manufacturing of parts.

Ordinarily, milling machines are powerful, precise, high-speed, and can handle large orders accordingly.

Thus, from a business perspective, you can save money and increase your profit margins when using metal milling process.

• Produces accurate components

The settings of milling machine and the cutting tool allow you to attain the utmost precision in metal milling.

Of course, this is advantageous because you get parts that match your exact application requirements.

• Less-laborious

Metal milling hardly requires relatively less labor since the machine carries out all the operations.

Notably, this process only needs the machine operator to adjust its settings accordingly to ensure an efficient method.

How Metal Milling Compare To Metal Drilling

Metal milling and metal drilling are among the common machining operations for producing different parts.

However, these two operations tend to vary in a wide range of aspects, which include the following;

• Metal milling process entails use of a multi-point rotary cutter to remove unwanted material from a workpiece rapidly.

On the other hand, metal drilling creates drilled holes in a workpiece using a single-point rotary drill bit.

• In metal drilling, drills use up and down motions with a rotating bit to create holes into the surface.

Metal milling machine bits also use more or less same motion, but they can also cut sideways to enlarge a hole or taper it off.

• In metal milling, the milling machines have tables, which you can use to secure your workpiece into place.

However, in metal drilling, you have to find an ideal surface to clamp the workpiece tightly.

• Metal drilling is relatively mobile, and you can do it in almost every location since the drilling machines and related accessories are fairly portable.

On the other hand, metal drilling only occurs at designated places such as workshops since even the small milling machine is still bulky.

• Metal milling nowadays uses integrated technology, thus guaranteeing high-quality results and final products.

On the contrary, metal drilling still uses the traditional drill bit movements, which in many instances tend to compromise quality of a final product.

Classification Of Metal Milling Process

Metal milling is classified under two main categories as follows;

• In face milling

It refers to the cutting process, which takes place at the end corners of the milling cutter.

This type of metal milling is usually used for cutting relatively flat surfaces into the workpiece or for cutting flat-bottomed openings.

• In peripheral milling

The cutting action in peripheral milling takes place along the circumference of the cutter to allow a milled surface cross-section to attain the cutter’s shape.

In this instance, the cutter blades scoop out material from the workpiece.

This type of metal milling process is suitable for cutting threads, deep slots, and gear teeth among others.

Choosing Metal Milling Tools And Equipment

Ordinarily, choosing the most suitable milling tool and equipment narrows down to a balance between quality, speed, and cost.

Some fundamental factors to consider when selecting a milling tool include the following;

Metal milling process

• Diameter

Often, a milling tool with a large diameter can mill the part relatively fast.

However, limitations tend to depend on part geometry.

• Tool coating

Different milling tools are coated with various products, essentially to protect them from wear.

For instance, titanium nitride coating increases the tool’s durability but is also a bit expensive.

• Helix angle

Angle of helix along with spindle rotation speed influence the cutting speed or feed rate.

If you are machining relatively soft materials, a steeper angle would be ideal.

• Number of flutes

Technically, flutes are the channels on a milling bit.

The more flutes, the higher the feed rate since less material is removed.

While at it, this increases the available diameter of the milling cutter, leaving less room for swarf.

Common Operations In Metal Milling Process

Metal milling involves a wide range of operations often performed to the workpiece to produce the desired part shape.

Mostly, these operations are defined by specific type of cutter used and its path to remove material from the respective workpiece.

Here are the everyday operations you are likely to come across in metal milling process include the following;

• Face milling
• End milling
• Boring
• Counterboring
• Chamfer milling
• Reaming
• Countersinking
• Tapping
• Angular milling
• Side milling
• Thread milling
• Straddle milling
• Profile milling
• Helical milling
• Gang milling
• Form milling
• Plain milling
• Milling key

Cutting Parameters In Metal Milling Process

Generally, speed and motion of cutting tools in metal milling are often specified through various parameters.

However, selection of these parameters is usually based on the workpiece material, tool size, and tool material among others.

Nevertheless, some of the common cutting parameters in this process include the following;

• Cutting speed – It is the workpiece’s surface speed relative to the cutting tool edge during a cut. Often, it is measured in square feet per minute.
• Feed rate – This refers to the actual speed of cutting tool’s movement relative to workpiece as the tool makes the cut, usually measured in inches per minute (IPM).
• Cutting feed – It refers to distance the cutting tool or workpiece progresses for every spindle and tool revolution. This parameter is measured in inches per revolution (IPR).
• Cut axial depth – This is the tool depth along its axis as it cuts.
• Spindle speed – It is the rotational spindle and tool speed often measured in revolutions per minute (RPM)

Common Metal Milling Defects

Often, defects in metal milling usually surface roughness or inaccuracies in a workpiece’s dimensions.

Several causes are attributed to such defects such as the following;

Dull cutter – The cutter teeth often wear down and become dull as it is used, making them less capable of making precision cuts.

Incorrect cutting parameters – If the cutting parameters in milling process are too high, the workpiece’s surface becomes rougher than expected results. Moreover, such parameters could lead to vibration and cause inconsistencies in the cut.

Unsecured workpiece – If the workpiece is not tightly secured in the fixture, milling friction may trigger it to shift and change the desired results.

Benefits Of CNC Metal Milling

Some of the benefits of CNC metal milling include:

• Cost-effectiveness

Ordinarily, conventional milling process needs an operator for every machine.

CNC milling, on the other hand, one operator can run various machines simultaneously, which reduces operating costs.

• Guarantees ultimate accuracy

CNC milling provides accurate results, which you can repeatedly repeat, thus ideal for mass production.

• Safety

Using CNC milling machines is quite safer since they are equipped and integrated with several safety features.

• Increases production output

The entire CNC milling process is automated, increasing manufacturing speed and quality.

This increases production output, which is fundamental, especially in mass production.

Recommended Surface Finishing Operations After Metal Machining Process

Metal machining process supports a wide range of surface finishing operations.

But the most commonly used options include the following;

• Vacuum deposition
• Electroplating
• Powder coating
• Thermal spray painting
• Anodizing
• Chemical plating
• Plasma electrolytic oxidation

How To Check Quality Of Machined Metal Parts

Ordinarily, machined metal parts are usually taken through various quality assessments to determine whether they meet the required standards.

Such quality tests often vary depending on the specific application of the machined parts.

However, the best method to establish quality of machined metal parts is by ensuring they contain quality standard certifications from reputable agencies.

Often, different countries give a mandate to various quality standard certification agencies to approve quality of products.

Such company certifications make it possible for you to determine whether the machined metal part meets the required standard.

Some of these certifications include; ISO, ASTM, ANSI, UL, CE, and RoHS among others.

For any questions or inquiry on metal machining, contact us now.