Hardware Guide for Aluminum Extrusions: T-Slot & Advanced

Extruded aluminum makes its way into a wide variety of applications that require an industrial-grade frame. It’s popular among engineers and designers for its modularity and ease of use.

What’s the secret to this flexibility? It’s in the hardware.

Although the profiles and brackets are important overall, it’s the ability to add nuts, T-bolts, and other accessories that makes these systems so versatile. Because there are many similar-yet-different options, let’s dissect the when, what, and how of using T-slot hardware (and advanced alternatives) effectively.

Why Use T-Slot-Style Hardware Over Other Systems?

There are many clear-cut cases where aluminum modular framing makes more sense than permanent assembly methods such as welding. Look out for them – even in heavy-duty projects. (We’ll explain why in a bit.)

Welded steel frames aren’t user-friendly. They require skilled labor to assemble, and multiple people and/or pieces of equipment to move the heavy weldments. Fixing a mistake or adding a modification later is a several-step process. 

Move away from welding and steel, and toward aluminum modular systems, when:

• Your turnaround time is tight
• You’ll need to disassemble & reassemble the structure often
• You might want additional features later

Aluminum extrusion hardware systems include traditional T-slots as well as more advanced, self-aligning systems for durability-minded projects. In either case, you receive the power to craft tailored structures, apparatuses, and machinery without intricate machining or welding. 

Basics of T-Slot Hardware & Other Aluminum Framing Fasteners

Long, aluminum profiles make up the bulk of an extrusion framing system, but their slots are the mounting point for even more important features.

Aluminum extrusions are cleverly designed to harbor a variety of fastening elements for a variety of components and accessories.

T-Nuts

T-nuts differ from standard nuts in that they fit onto a T-shaped profile, after which you can position it anywhere along the profile’s length. They’re a staple of bracket, panel, and accessory mounting.

T-slot nuts come in subtypes with their own use cases. Some unique options include:

• Sliding T-nuts – These slide into the side slot of a profile. This “stepped” nut has a large surface area, making it a sturdy option for heavy-duty mounting and support.
  
  
• Drop-in T-nuts – These go into the T-slot from the top, allowing for post-assembly insertion without disassembly. They’re particularly useful when you want to add an accessory to an existing structure, or when you missed a connection point during assembly. Most designs include a flange that sits flush with the profile surface, ensuring a snug fit.
  
  
• Spring-loaded T-nuts – These have a small coil mechanism so that you can roll them into the end of the extrusion. The spring keeps the nut in alignment, even before threading of the bolt. These are ideal for fast-paced, repetitive, or awkward assembly situations, including vertical or overhead applications where gravity might render a regular drop-in nut useless. They’re a lifesaver when you have to mount a large, flat surface.

Drop-in nuts are trickier to use than standard nuts – that’s the price you pay for the added flexibility. To install a T-nut:

1. Screw it loosely onto the component
2. Align the nut and slot it into the profile
3. Carefully turn the fastener head until the nut has turned 90° and is seated in the slot
4. Finish tightening the fastener

Fasteners

Now you need something to connect all those nuts to the frame and its accessories. 

In the context of aluminum extrusion hardware, there are important differences between bolts and screws. The size and type of screws, bolts, or washer you use will determine the reliability of your connection.

If using traditional T-slots, there are two steps you must complete before installation:

1. Tapping extrusion #1
2. Drilling a hole in extrusion #2 so you can reach the fastener head with a hex key

Plates

Joining plates allow you to reinforce aluminum extrusion joints at various angles without machining. They’re a common site on machine bases and other industrial structures where vibration creates a durability risk. They also provide a flat, stable surface for mounting other components, machinery, or equipment to the frame.

Common types of framing plates include joining, gusset, base, and mounting. You might also include end caps here – they aren’t a plate per se, but they do cover an extrusion’s ends for a clean, finished look.

Considerations in choosing plates for your structure’s frame include:

• Material: Most plates on a structural frame are made of aluminum or steel. Aluminum plates are lighter and easier to work with, while steel plates offer high strength and rigidity. However, self-aligning aluminum systems are stable enough to mimic the rigidity of steel weldments, making for a nice hybrid option of lightness and stiffness.
  
  
• Size: The thickness and overall dimensions will depend on the load requirements. Thicker and larger plates are necessary for higher stress loads. Again, this is where you may prefer an advanced-self-aligning system over your current solution. A single such assembly can replace stitched-together weldment-and-T-slot frames, allowing you to use a plate with less footprint.
  
  
• Compatibility: Obviously, the plate must be compatible with your chosen profile series and size. You don’t want any clearance or misalignment coming from those bolt holes.

(Related Resource: How to Pick Angle Brackets for Framing Systems)

Tips for Taking T-Slot Hardware to a Higher Level

With aluminum frame hardware, how you use it is just as important as what you use.

Here are some points to consider as you search for the fastest, most cost-effective way to complete your project:

Use Size & Strength in Moderation

Watch out for wasteful practices when it comes to sizing fasteners and shoring up your structures.

T-slot nuts, for example, are available in many sizes. Examine the size of the threaded hole to ensure it can accommodate the threaded stud you plan to use. Don’t waste precious lead time sourcing the wrong part!

Don’t assume you need to err far on the side of bigger and stronger. In T-slot framing, bolts are almost comically oversized to give the illusion of strength. In reality, an M6-size bolt with a 12.9 strength rating will match up surprisingly well with an M8 bolt with a 10.9 rating.

If you care about strength and stability, it’s better to pay attention to the engineering of the connections, rather than the size. There’s a reason self-aligning frames get away with sleeker builds with no cross-bracing.

Ignore (Most of) the Noise of Variety

The variety of T-slot hardware options is staggering – and they all seem to do slightly different things. Sometimes they do the same thing, but are a slightly different material, which can also be a pain. 

For example, 80/20 aluminum hardware listings include the same corner in die-cast aluminum and die-cast zinc. For the purposes of modular framing, there’s not really a performance difference.

Likewise, it’s common for T-slot hardware sellers to show off a huge variety of bolts. These nearly countless variations of almost-identical products (i.e. die-cast zinc and die-cast aluminum versions of the same bracket or screw). Yet each variation doesn’t add much value, and makes ordering more confusing and time-consuming.

At least many of the products are cross-compatible with other systems. This is slightly less true with self-aligning framing, but there’s a growing number of universal products in that realm, too.

(Tip: The hardware’s product ID usually tells you what category of T-slot width it falls under. Check this to gain an understanding of compatibility with a particular profile size.)

Speaking of self-aligning extrusion framing, taking this route can help you avoid many of the selection hassles of T-slots. Instead of making you waste 30 minutes researching the parts you need, self-aligning system manufacturers package the hardware right with your order. With all connection components presorted, there’s no work to organize the hardware when it arrives at your doorstep.

Cut Down on Assembly Trial-and-Error

Finally, some further tips to get you up and running more quickly:

• When you anticipate adding to or moving the hardware someday, go with T-nuts you can drop directly into the assembly. This way you’ll avoid having to disassemble the structure.
  
  
• Choosing self-aligning aluminum over T-slots also cuts down on assembly and check-in time. If you have to check in one self-aligning kit, that’s a simple process. Some T-slot sellers will ship everything in one kit, but when it arrives it’s still segregated in the same unhelpful way. (Yet the seller does this at an extra cost.)
  
  
• Come assembly time, double-check that you mounted all assembly plates correctly and didn’t miss any fasteners. In the case of self-aligning framing, don’t forget any of the angle nuts you’ll need to connect brackets later in assembly!

Now, on to Bracketing & Profiles

The modular format of aluminum framing enables swift and straightforward building, breakdown, and modification. In the right application, and with the right engineering, it can be the perfect solution for prototyping, automation, and on-the-move designs. What’s more, self-aligning framing adds refined and professional performance and appearance that isn’t possible with classic T-slots.

Now that you know how to use it, get going! Learn more tips on the design of structural, modular systems at our blog library: