CNC Machining 101: Welding vs. Riveting

When designing something that requires two pieces of metal to be brought together, it’s important to consider whether they will be welded or riveted. Welded joints and riveted joints are two commonly used permanent joining processes. Both welding and riveting have strengths and drawbacks that will create a part that lasts a long while depending on the project at hand.



CNC riveting is a mechanical process that permanently fastens geometric shapes ranging from simple to complex. Rivets are cylindrical metal shafted tails or mandrels that have dome-shaped heads. These types of fasteners create a watertight join when connected through the glowing hot drilled holes. When the metal cools, the rivet contracts, and the two parts become one. Riveted structures are generally heavier in weight. Blind rivets are used in a variety of metals including aluminum steel, stainless steel, and copper. A hole is drilled and then the rivet is set inside of the hole. The machine or fabricator then pulls the mandrel of the rivet to reach the designated peak force until it eventually snaps off. This leaves a “blind” or flush-looking properly installed rivet. One of the biggest advantages to riveting is that there is no way to under-torque rivets. A rivet will install perfectly every time as long as the correct diameter and grip range are chosen.

Riveting is one of the oldest technologies, and was used for ships, structures, and vessels before World War II. CNC riveting can be used for a variety of operations such as for aircrafts, structural beams, small electronics, RVs, and submersibles. Many CNC riveting machines are made for manufacturing lines, making turn-around time faster with a higher degree of automation.


Welding is the more familiar method of fabrication widely recognized in the industry to join metal materials. Welding also fuses two pieces together, either manually or with the help of a CNC machine. Instead of heating up the individual parts of metal that are being formed together, welding uses an external high heat source that melts the pieces to conjoin them. Welded joints always provide very high efficiency compared to a riveted joint. When thinking about aesthetics, welding will always give a smooth, visually-appealing structure while also having comparative strength to a rivet. Welded structures tend to be light in weight compared to riveted structure due to the fact that in welding, gussets — the connecting components — are not being used. Alterations and additions can easily be made within the welded structure, whereas once a rivet is in place, there is no longer room for altering. Some disadvantages to welding include uneven heating and cooling involved in the process. This factor can inhibit additional stresses to the metal. The inspection for defects tends to take longer for welding structures due to the heating and cooling process, which will also result in more manual labor for the fabricator.


Both Great: Depends on Project & Finished Appearance Desired

 Many riveting structures were replaced by welding after World War II because welding was less time consuming. Riveting requires holes being made, proper assembly with the rivets, pressure, and correct grip diameters before being assembled, whereas welding only requires assembly without much preparation. The loss of metal due to the hole in the rivet structure ultimately makes it a weaker bind. Welding does not consist of any metal loss like so, leaving it with a rather stronger connection. Welding, whether using CNC machines or fabricating manual labor, tends to be a quicker and generally cheaper process due to fewer steps and parts needed. Drilling holes, inserting the rivets, heating the protruding end — all these steps take up a substantial amount of time in comparison to a weld. However, for very thin sheet metal, welding might not be sufficient as its possible to burn through. Rivet holes tend to stretch and have a more calculated clearance when welding may not be the best alternative. As with most things in engineering, not everything is a ‘one size fits all’ — and with riveting and welding that phrase most definitely holds true. Here at MFI we pledge to utilize the best method for conjoining metals based on the end user’s desired requirements.



CNC Machining 101: Milling and Turning

cnc machine
CNC (Computer Numerical Control) machining is a subtractive manufacturing technology where parts are created by removing material from a solid block, called the blank or workpiece, using a variety of methods. The removal of material has significant implications on the benefits, limitations, and design restrictions of CNC. Since CNC machining is a digital manufacturing technology, it produces high accuracy. The high level of automations required makes CNC machining competitive in price for custom parts and medium volume projects.

The most common metals used for basic CNC machining are aluminum, steel, brass, and plastics. However, almost every material can be CNC machined. Firstly, the engineer must create the CAD file for which the metal will be shaped. CAD is Computer-Aided Design software for engineers or architects to create two-dimensional or three-dimensional models. Once the design is complete, the machinist turns the CAD file into a CNC program and sets the machine. The CNC machine then executes the CAD file design completely automated, removing the materials necessary to create the end product.

When CNC milling, the workpiece is held stationary directly on the machine bed. Milling incorporates the technical aspects of both drilling and cutting processes, and CNC milling uses a rotating cylindrical cutting tool just like in drilling. Precise positioning and alignment are key for manufacturing accurate parts and special metrology tools (touch probes) are often used for this purpose. Material is removed from workpiece using cutting tools or drills that rotate at high speed. The tools are attached to a spindle, which moves along a linear axis. The cutter and workpiece move along several axes with tight tolerances. If the model has features that cannot be reached by the cutting tool in a single step, then the part needs to be flipped and the prior steps then repeated. After milling, the part is then sent off to be deburred. Deburring is a manual process of removing the small defects on sharp edges due to material deformities from the CNC machining.

CNC turning is when the part is mounted on a rotating chuck and materials are removed using stationary cutting tools. The metal part to be worked on is then placed along the center axis. Like milling, a CAD model and blank material are loaded in the CNC machine. The part starts to rotate at high speeds and a stationary cutting tool traces its profile, gradually removing material until the designed CAD model is created. CNC turning systems (lathes) are normally used to create parts with cylindrical profiles. Non-cylindrical profiled parts can be manufactured using a multi-axis CNC turning center, which are furnished with milling tools. Milling and turning are very similar processes but different in how the part is executed.

Drills and other cutting tools are used often along the center axis to create different geometries when milling and turning. The most commonly used milling tools in CNC include the flat head, bull head, ball head, drills, slot cutter, and fact cutters. Drills are a quick way to create holes. Flat heads, bull heads, and ball heads are used to create the grooves, cavities, and walls. The difference in each of the head’s geometry allows different, detailed features. A slot cutter’s diameter shaft is smaller than the diameter of their cutting edge to cut T-slots and undercuts from sides of vertical walls. Face milling cutters are used to remove material from large flat surfaces. With a larger diameter, they require fewer passes to machine large areas, producing clean flat surfaces.

CNC machining not only increases productivity, but it saves time and money in the process. It can produce parts with tight tolerances, making it ideal for high end applications. CNC machining is great for both one-off jobs and low-to-medium volume production, especially for metal prototypes as it is the most price-competitive option. At Merchants, depending on the project requested, our talented fabricators utilize CNC machining milling and turning to make a variety of parts.


Sheet Metal Finishes for Aesthetics and Longevity

sheet metal finising
You may think sheet metal finishes sole purpose is for aesthetic. Why else would it have that beautiful matte finish that’s so symmetrical and perfect? You may not be aware that certain finishes aren’t just for eye catching designs — they are also for protecting the product depending on its use. For example, sometimes a special chemical coating is used to change the surface of the metal to make it more adaptable for its intended use. The process of applying a specialized finish to sheet metal is not new. In fact, sheet metal finishes are everywhere. Generations of manufacturers utilize different finishing techniques to enhance their corrosion resistance, scratch resistance, and overall functionality. We’ve outlined some neat finishes and coatings to look out for when designing the functionality and appearance of a fabricating project.

Chemical conversion coatings have specialized purposes tailored to particular types of sheet metals. The most common types are anodized, chromate, zinc, and passivate. These coatings help limit the corrosion that would normally happen when steel, stainless steel, or aluminum are exposed to elements. For instance, if you want to improve electrical properties of stainless or aluminum parts, chromate would be the chemical treatment used. To improve corrosion resistance yet also add some color for aesthetics, you’d want to anodize.

Powder coatings are one the most common sheet metal finishes. First, a small electrical current is run through the metal. Then, a powered polymer pigment is sprayed on with a nozzle, forming a bond with the metal through electrostatic attraction. Powder coatings top paint for aesthetic reasons due to quick drying and a more uniform solid finish, and they come in several different colors. Powder coatings are decorative and protective from corrosion and heavy usage.

Silk screening is strictly for aesthetics, and the process is the same way people add logos to T-shirts. A fine mesh screen allows ink to transfer through, but only in designated areas that you choose. It is recommended that you choose a smooth powder coat finish before silk screening so the graphics produced have a greater effect.

Anodizing is an electrochemical process that increases the corrosion resistance of a metal part by forming a layer of oxide on its surface. Submersing aluminum in an acid electrolyte bath while passing an electrical current through it forms an aluminum oxide coating right from the aluminum itself. The results are a hard, durable coating that’s resistant to corrosion and never peels or chips.

Metal plating is one of the most common metal finishes. It’s when you cover the surface with a thin film of another metal. These metals usually consist of nickel, silver, gold, etc. to make it corrosion resistant in certain environmental conditions. Metal plating is typically used to decorate certain projects, like jewelry, instruments, electronics, and furniture.

Brushed metal and metal polishing finishes are similar, but not entirely the same. Brushed metal finish is ideal for removing imperfections from the surface using special abrasive brushes and is generally used to achieve a granular/scratched texture. Metal polishing can be seen as removing imperfections as well, but on a smaller scale. Tending mostly to stainless steel, copper, and aluminum metals, polishing and smoothing entire objects is generally used to give a really glossy, polished finish to damaged or neglected metals.

Dual action or directional finishing is utilized after the course of handling the material after it gets nicked or scratched.  Removing these defects involves a mild grinding of the surface in a non-directional or random pattern.  In effect, it adds small scratches randomly across the entire surface.  Direction finishing is the “graining” or scratching of the surface in a particular uniform direction.  For example, a widely recognizable use of this type of directional finishing is on stainless steel kitchen appliances.  The appearance can vary given the grit or grain size of the abrasive use to produce the finish.

There are many different types of metal finishes to which metals are subjected. Originating from engineering, a metal component passes through the sheet metal bending, punching, threading, and other processes before arriving to the final phase of work: the metal surface finishing process. A variety of factors should be taken into consideration when choosing a metal finishing process. If your operation requires a quick turnaround time, you’ll need to choose a process that is compatible with tight deadlines. Another factor is the hardness of the metal or other material you’re working with. A process that is overly abrasive could damage the metal, while one that is too gentle may not achieve the preferred result. Here at Merchants, the option to choose any of these finishes for your desired project is attainable. Our master fabricators have a solid reputation for superior quality parts and finishes along with excellent turnaround time and delivery.



Not All Welding Techniques are Created Equally

Welding can be called an art form. Like art, there are many different ways to weld metal. Welding is the process by which two pieces of metal can be joined together through the use of extreme heat. Sometimes utilizing specific gases and metals can also cause the metallic structures to become one. Some welding techniques call for arc welding, tungsten inert gas (TIG), spot welding, and underwater welding.

Arc welding is a fusion welding process used to join metal. An electric arc from an AC or DC power supply creates intense heat of around 6,500°F that melts the metal to join it together. These metals react chemically to oxygen and nitrogen at such high temperatures. If you are familiar with what soldering is, you may assume that this process of welding is essentially a larger format of soldering. These two operations are fairly similar, but sub-techniques vary. The big difference between soldering and welding is melting points and metals used. Soldering is similar to welding because both use a filler metal into the joint; however, not all welding involves fillers. The filler can be aluminum silicon, brass, copper, copper-silver, gold-silver, nickel alloy, or silver. Unlike arc welding, soldering uses a lower temperature to join metals. While both arc welding and soldering heat up electronically, soldering metals tend to be softer and more conductive. Popular soldering metals include silver, copper, brass, and iron. Soldering also doesn’t hold as strong of a bond as welding because it is not connected mechanically through fasteners like bolts, rivets, or screws. Soldering is usually more small scale, used to form a permanent connection between electronic components.

Tungsten inert gas welding (TIG) became popular in the 1940s for joining magnesium and aluminum. Using a gas shield protects the weld from harmful gases in the atmosphere such as oxygen, carbon dioxide, nitrogen, and water. Also known as noble gases, inert gases are colorless, odorless, and non-chemically reactive. Argon and helium are most used in welding. Argon is present in 1% of air and is a by-product of the air-reduction processes used when producing oxygen. This gas is specifically good for deep pits in the metal or welding in flat positions. Argon is most suitably used with aluminum and nonferrous metals. Adding helium improves the heat properties of argon. However, pure helium is ideal for copper, magnesium, and aluminum. Semi-inert gases have low reactivity like hydrogen, oxygen, carbon dioxide, and nitrogen. Semi-inert gases can be used pure but yield better results when used in combination with other pure inert gases. Combining gases such as argon, carbon dioxide, and hydrogen, for example, can raise the temperature and improve weld penetration. Anyone interested in welding needs to be aware of the roles these gases play and how exactly they interact with each other. The chemistry — the small details — are very important in the world of welding.

Spot welding is one of the oldest techniques used for welding. It’s primarily used for joining parts that are up to 3mm-12.5mm in thickness, and it works through conductive heating that’s created by an electrical current. Two copper electrodes hold the two pieces of metal together as copper is high in thermal conductivity with low electrical resistance. Welds are repeated at regular intervals to effectively solidify the metal into one secure joint. Steel is a great metal for spot welding as it has a higher electrical resistivity for lower thermal conductivity than the copper electrodes, making it relatively to weld.

Underwater welding is actually not as much different from dry land welding as you would think. Many people instantly start getting concerned with the danger of mixing water and electricity. This welding method involves years of training and abundance of knowledge, as well as a certification from the commercial dive school. This is said to be one of the most dangerous occupations in the world. In underwater welding, a dry chamber system is utilized, and hyperbaric chambers are used to prevent water from entering the work area. These chambers can typically hold up to three welders at a time. The chambers are pressurized by the crew on land to exchange air and replace it with new air and minimize potential pressure sickness. Wet welding on the other hand isn’t always done in a pressurized chamber. It’s quicker and cheaper, but also trickier as it cools down more quickly due to the water. Underwater welders and wet welders are able to identify and deal with what comes at them relatively quickly which is what keeps them alive. So, if repairing pipelines, ships, sea habitats, and nuclear power facilities — with a touch of an adrenaline rush — interests you, be warned to approach this trade with much caution and grit.

Different techniques are obviously utilized based on the particular project at hand. It’s important to know and understand all the necessary precautions before beginning welding. Safety and knowledge of chemistry are of main importance when utilizing which procedure will suit your needs most. Regardless of what the task at hand is, MFI has exceptional fabricators with decades of experience ready to tackle any requirement requested of them.

Sheet Metal Fabrication 101

Sheet metal fabrication is the process of turning flat sheets of steel or aluminum into metal structures by cutting, punching, folding, and assembling. Sheet metal can be shaped or stretched into nearly any shape which is normally done by cutting and burning the metal.

Sheet metal fabrication uses press brakes to create bends and angles within the metal. Press brakes are tools that deliver different level of force to bend such metal. Mechanical, pneumatic, hydraulic, and CNC are common forces used with metal bending. The main advantage to mechanical press brake is speed and accuracy. Pneumatic is when a compressor is used to supply air power for bending the metal sheets. This type of press brake is often used when less pressure is needed, and best for bending small pieces of metal. Hydraulic press brakes are usually best used for precise metal sheet bending. Computer Numerically Controlled (CNC) machines produce very accurate results being safer and easy to use; and able to bend from a couple millimeters across to sections that are meters long on the larger machines. While press brakes are the most common way to create bends and angles within the sheets, other ways to create these angles include rolling machines, stamping, folding, and machining.

Aside from press brakes creating various levels of bends within the sheets, another important aspect of sheet metal fabrication is welding. Welding techniques are used in sheet metal fabrication to prevent warping of the metal or other deformities that may arise. Many people use fabricating and welding as interchangeable verbs, but that’s not always the case. Fabrication is the process of creating a project out of metal, and welding can be a singular operation involved during that process. Since welding is a sheet metal forming technique, it’s a cohesive necessity involved with sheet metal fabrication.

Sheet metal fabrication is a multi-step job that requires several tools and skilled experts working together to completion. An engineer creates the initial blueprints that will then be used to determine which sheet metal product specifications are necessary for rough drawings to be made. Those rough drawings then need to be checked over by many different eyes to make sure all requirements are correct. The final drawing will include in-depth calculations of the metal stress levels needed and load limitations. The metal fabrication process involves cutting, bending, joining, and finishing. The cutting process utilizes shear force either by shearing, punching, or blanking depending on the task. It’s also possible to cut sheet metal without shear force. These ways of cutting involve using water jets, plasma, and laser beams. These three methods specifically work best to produce precise cuts for large, industrial scale projects.

When the sheet metal is formed into the desired shape for the project, the ends of the sheet metal need to be joined together. This is the stage where the welding technique comes into play. In many projects, the completed piece is a combination of various pieces. They become one either by welding, brazing, riveting, or adhesives. Lastly, once the project has come together, it’s important to pick the right finishing. The finish of the metal depends on the project. Aside from aesthetics and protection, many treatments are used to increase resistance or conductivity, making these treatments an important final step to finishing the job.

At Merchant’s Fabrication, we are proud of the high quality services we offer and are meticulous with craftsmanship. Our highly talented master fabricators have over a decade of experience and consistently deliver high quality, on-time projects. Serving the aerospace, medical, food and beverage, manufacturing, and paper industries, Merchant’s is able to support our customers needs to the exact detail requested.