Glass Spider Fittings: Material Grades, Manufacturing Process, Finishing Treatments and Types

Glass spider fittings are the unseen components that hold large glass panels in modern architecture. These fittings allow designers to create the transparent and open building exteriors and interiors that are popular today. The spider fittings for glass are what connect the panels to the building’s main structure. This article will explain the different aspects of these fittings, including the materials used to make them, the manufacturing methods, the types of finishes they can have, and the various styles and sizes that are available for different projects.

What are Glass Spider Fittings?

Glass spider fittings are a kind of structural hardware used to support glass panels in a way that makes them look like they are floating. The name “spider” comes from their shape, which has multiple arms that spread out from a central body. These arms are designed to hold the corners of the glass panels, attaching them to a main frame or to a building’s structure.

This system of holding the glass gives a building a light and open appearance because there are no heavy frames blocking the view. The spider fittings are a way to make a building’s skin from glass. These specialized components are a key part of point-fixed glazing systems, which use small, discreet fasteners to anchor glass sheets directly to a support structure.

The main body of the fitting, often shaped with two or four arms, is the core of the system. At the end of each arm, a crucial component known as a rotule or articulated bolt is installed. This bolt passes through a precisely drilled hole in the glass panel. The rotule’s design allows for a degree of movement, which is essential to prevent stress on the glass. The flexibility helps the system absorb forces from wind, thermal expansion and contraction, and minor structural shifts of the building itself.

By distributing loads evenly and accommodating these movements, spider fittings guarantee the safety and long-term stability of the glass facade. Their minimalist design and high-strength engineering allow architects to realize complex and visually stunning facades, canopies, and skylights that maximize natural light and transparency.

Common Material Grades for Glass Spider Fittings

Stainless steel is the main material for making glass spider fittings. This material is strong and can withstand rust and corrosion. There are different grades of stainless steel, and the best one to use depends on the project’s location and what it needs.

Grade 304

Grade 304 is a common type of stainless steel for fittings. Its composition includes chromium, which helps it resist rust, and nickel, which adds to its toughness and durability. This makes it a cost-effective option for projects where the glass spider fittings will be used indoors and are not exposed to harsh conditions.

For example, Grade 304 is often used for glass railings inside a shopping mall, for a glass partition in an office building, or for shower enclosures in a home. It is also found in internal glass staircases and display cases in retail stores.

In these settings, it provides the needed strength and a lasting appearance because there are no corrosive elements like salt or pollution to cause damage.

Grade 316

AISI 316, also known as marine grade stainless steel, this material has better resistance to corrosion. It is used for outdoor projects, especially in places near the ocean or in areas with a lot of pollution.

The higher resistance comes from an added chemical element called molybdenum. This element helps protect the steel from damage from chlorides, which are found in salt spray, air pollution, and de-icing salts used on roads in winter. This makes Grade 316 a suitable choice for glass canopies in a city center, a glass facade on a building near the coast, balcony railings for a seaside apartment, or glass panels on a public pedestrian bridge.

The higher material cost is a balance for the longer lifespan and reduced need for upkeep in these aggressive environments.

Grade 2205

This is a more advanced material known as duplex stainless steel. It has a special structure that combines two types of steel, which makes it much stronger and more resistant to rust than Grade 304 and 316. Grade 2205 is used for projects where the fittings need to handle very heavy loads or where they will be in very harsh conditions. The extra strength allows it to support larger and thicker glass panels.

For instance, it might be used for a large glass wall that needs to withstand strong winds in a high-rise building, for a skylight canopy in a region that gets heavy snow, or for glass structures in industrial areas that have a high level of chemicals in the air. Its high performance makes it a top choice for demanding architectural projects where both strength and long-term durability are a concern.

Other Grades

While Grades 304, 316, and 2205 are the most common for glass spider fittings, other types of stainless steel are sometimes used for special needs. For example, Grade 303 is an easy material to machine, which can make it a choice for parts with many fine details. Another type is Grade 420, which can be made very hard. This hardness makes it a good option for parts that need to resist wear and tear. However, these grades may not offer the same level of rust protection as the more common grades, so they are only used when their specific qualities are more important for the project.

Manufacturing Process of Glass Spider Fittings

The making of glass spider fittings is a detailed process that helps them meet strict standards for their use in buildings. The process transforms raw stainless steel into a finished part.

Investment Casting and Machining

The first step in making the fittings is called investment casting. This process is used to make the complex shape of the spider fitting with a high level of detail and a smooth surface finish. The investment casting process is a series of steps that begins with a wax model of the final product.

• A wax mold of the fitting is made. The wax is injected into a master die to get the exact shape.
• The wax mold is covered in multiple layers of a fine ceramic material to form a solid outer shell. This shell has the exact shape of the fitting’s details.
• The ceramic shell is heated in a furnace until the wax inside melts and runs out. This step is also called “lost-wax” casting.
• Molten stainless steel is then poured into the empty ceramic mold. The liquid metal takes the shape of the fitting as it cools and hardens.
• Once the steel has cooled, the ceramic shell is broken away from the metal, revealing the raw fitting.

After the fitting is cast, it goes through machining. This step uses computer-controlled tools to make the part fit exact dimensions. This is where holes for bolts and pins are made with high accuracy, and surfaces are smoothed to get the correct shape.

Assembly

Some spider fittings are made from more than one piece. For example, a two-arm fitting might have two separate arms that are joined to a central body. In these cases, the parts that were separately cast and machined are put together to form the final product. Assembly might involve bolting the parts together to get a full fitting.

Quality Control

After the fittings are made and put together, they are checked to make sure they are of high quality.

• The fittings are measured with special tools to make sure they have the right dimensions and that the holes are in the right places and have the correct size. This is important for a proper fit with the glass panels.
• They are inspected for any defects on the surface of the metal, such as cracks or rough spots from the casting process.
• Some tests may be done to confirm the strength and other qualities of the fitting. For example, a sample might be tested for its tensile strength to see how much force it can withstand before breaking.

Finishing Treatments of Spider Fittings

After the manufacturing process, spider fittings can receive different finishing treatments. These finishes change the way the fitting looks and also add a layer of protection to the metal. The choice of a finish depends on the design of the building and the environment where the fittings will be used.

Mirror-Polished Finish

This finish is made by rubbing the surface of the metal with fine abrasive materials. The process starts with a rough sanding and moves to finer and finer polishing until the surface is very smooth. The result is a highly reflective surface that looks like a mirror. The mirror polish finish is often chosen for its bright, shiny look, which can give a modern and clean feel to a building. It is a finish often used for high-end projects where the look of the fitting is as important as its function.

Satin Finish

This finish is made by brushing the surface of the metal with a special tool or by using a fine grit sandpaper. The brushing creates a soft, matte look with a slight texture. The satin finish is popular because it has a subtle shine that is not as reflective as a polished surface. A satin finish is less likely to show fingerprints or small scratches, which makes it easy to maintain and keep clean. It is a good choice for projects where a more understated and contemporary look is desired.

PVD Coating

PVD stands for Physical Vapor Deposition. This is a modern way to apply a finish to the fittings. The process takes place in a vacuum chamber, where a metal (like titanium or chromium) is vaporized and deposited onto the surface of the stainless steel spider fitting. This creates a very thin but very hard and durable coating. PVD can be used to give the fittings different colors, such as gold, black, or bronze. The PVD coating also adds a layer of protection to the fitting, giving it more resistance to scratching and corrosion than a standard polished or satin finish.

Types of Spider Fittings and Sizes

Glass spider fittings come in a variety of types and sizes to match the needs of different projects. The number of arms on the fitting and its overall size are two of the most common ways to classify them.

Categorization by Arms and Application

The most common way to group fittings is by the number of arms. The number of arms tells you how many glass panels the fitting can hold at a single point.

• Two-Arm Spider Fittings: These fittings are used to connect two glass panels together. They are often used for linear connections, such as on a corner of a glass wall or where two panels meet in a straight line. They are also used at the top or bottom edges of a glass facade to hold the glass to a building beam.
• Four-Arm Spider Fittings: This is the most common type of fitting. It is used at a central point where four glass panels come together, such as in the middle of a large glass facade. The arms spread out from a central body to hold each of the panels.

Spider fittings are also designed for their specific use.

• Canopy Spiders: These fittings are made for glass canopies that extend from a building. They are shaped to support sloped glass and help direct rainwater away from the structure.
• Skylight Spiders: Used for overhead glass structures like skylights, these fittings often have special features for sealing and drainage to prevent leaks.
• Curtain Wall Spiders: These fittings are used to create large, seamless glass facades on the outside of buildings. They hold the glass panels to the main structure of the building.

Sizing and Custom Fittings

Spider fittings are made in a range of standard sizes. The size of the fitting is a factor of the glass panel’s size, its thickness, and its weight. The size of the fitting is based on the distance from the center of the fitting to the end of each arm. This distance is called the “center to center” or “c-c” dimension. For example, standard sizes include 150 millimeters, 200 millimeters, and 250 millimeters. A larger, heavier glass panel will need a larger, stronger fitting to hold it safely. For a smaller glass display, a smaller fitting is enough.

In addition to standard sizes, custom spider fittings can be made for unique projects. When a design needs a special shape or a specific size, a custom fitting can be created. This process starts with a design and a technical drawing to make sure the custom part will work for the project. Custom fittings are often used for complex architectural designs that standard fittings cannot support.

Choosing a Glass Spider Fittings Manufacturer

When you need to get glass spider fittings for a project, picking the right manufacturer is a big step. The quality of the fittings has a direct effect on the safety and look of the final building. Here are a few things to consider when you make this choice.

Experience and Reputation

A manufacturer with a history of making good products is a good place to start. A company that has worked on many projects and has a long list of completed jobs shows that it has a good understanding of what is needed. You can look at their portfolio to see the kinds of buildings they have helped with.

Taiyuan SIMIS Investment Casting Co., Ltd is a professional investment casting foundry in China with over 40 years of manufacturing experience. At SIMIS, we specialize in offering high-quality stainless steel castings, including both custom and standard glass spider fittings of various types and sizes.

Quality and Testing

A good manufacturer has systems for checking the quality of their products. They can give you reports on the material grades used for their fittings. They may also do tests on the finished fittings to confirm their strength and how they perform under load. This information is important for making sure the fittings meet all building codes and safety standards.

Taiyuan SIMIS is an ISO9001 accredited company. We conduct 100% inspection on all castings. This means that every glass spider fitting we cast goes through rigorous testing and inspection before shipping out to customers.

Technical Support

The best manufacturers offer help beyond just selling the product. They can give technical support to architects and engineers. This support can be helpful in the design phase when you are picking the correct type of fitting or deciding on a size. They can also answer questions during the building process. Having this kind of help can make a project go more smoothly.

Our brilliant customer support has made us a successful casting foundry and supplier. At SIMIS, we strive to make every client satisfied. We answer any technical questions or quality-related queries promptly. We also regularly update on production progress and lead times, and all shipping can be tracked with a provided tracking number.

Product Range and Customization

A manufacturer that has a large selection of fittings is helpful. A wide range of products in different sizes and types gives you more choices for your design. If your project has a special design, finding a manufacturer that can make custom fittings is a good idea. This lets you get a part that is made just for your building’s needs.

Here at SIMIS, customization is our expertise. We produce castings 100% based on customers’ drawing requirements and material specifications. We can help customers develop their ideas and designs and turn concepts into products. For glass spider fittings, we offer fully comprehensive services, including tooling design and manufacture, machining, surface treatments and more.

Contact us and speak with experts today to get your project started.