T-Slot extruded aluminium profile joints – Stronger connection

Profile Joints – Part 2

As a person who is regularly building all manner of things using T slot aluminium extrusions, I occasionally come across a situation where a simple joint using a fixing screw just isn’t going to cut it.  Today I am going to introduce you to just a few of the many different methods of joining T slot aluminium profiles using items found in the Fixing Accessories section of the Alusic catalogue.

Late last year I was putting together a batch of custom designed workbenches when the owner announced that they wanted an LED light panel mounted about 1200mm above the main work surface of each workbench.  No problem, I thought.  Just add a pair of upright sections at the back of each workbench, build a frame to hold each panel and attach to the uprights.

That was all fine until it was let slip that some of the workbenches were to be indirectly attached to pieces of equipment that would put some not insignificant vibrations into the workbenches a number of times per day.  I quickly realised that the simple jointed cantilever design I’d thought of would likely not cope with the dynamic loads generated by oscillations, caused by vibrating machinery, of the panel and frame on the uprights.  Even though that simple jointed cantilever design would be fine with the panel as a static load.

So, a quick design review later.  It was decided to use fixing angles (084.305.033) for the main joints and make braces for the uprights using some joint angles (084.305.011).

fixing angle 43 x 86  joint angle for 40 x 40 profile


The fixing angles made the joints very much stronger than they would have been otherwise.  Using joint angles to make braces for the uprights stiffened the structure enough to almost eliminate oscillations that would be generated by the vibrating machinery.  Thinking about it now, just the braces may have been adequate to keep oscillations, and hence joint loads, down enough for the original simple joint design to cope.  Oh well … I think there is a saying in the engineering world that has something to do with “belts and braces”.

A few months after that, the same owner said they wanted some more workbenches (different design of course) also with the LED light panels.  This time though, they wanted to be able to adjust the braces up or down a little for operator head clearance.

At first that seemed a bit complex, not to mention costly.  A stock of different length braces to be removed and replaced by maintenance people as and when required.  I could see there would be no way to guarantee that adequate length braces would not all soon be replaced by the shortest braces, or even removed completely.  Not a viable option in my view.

Then the Alusic catalogue came to the rescue.  Instead of using a joint angle at the end of each brace and making different size braces it was decided to use a screw swivel joint (084.311.010) at the end of each brace.  That would ensure every LED panel support would be adequately braced as well as have a small amount of adjustment using just a hex key.

brace using screw swivel joints

To get your own PDF of the Alusic catalogue, fill in your name and email address on our site main page and we will send an email with the download link.










T-Slot extruded aluminium profile joints – Standard connection

Standard Connection

The standard connection is the simplest and most cost effective joint for Alusic aluminium T slot profiles.  It is a perpendicular (or square) joint using a single socket head screw (fixing screw) without the use of any fancy accessories.

In this simple joint the central hole in the first profile piece to be joined has a thread tapped into it.  The thread -diameter & depth- is to suit the fixing screw being used.  In the second profile piece, a hole is drilled perpendicularly through at the desired location of the joint.  The hole is to allow a hex key access to tighten the fixing screw.

T-Slot extruded aluminium profile joints - Standard connection - aluminium extrusion

Details of how to make one of these joints are at this blog post.

Since this joint type is the simplest and most cost effective, it is by far the most commonly used in light, medium, and many heavy duty applications.  For more heavy duty and not so simple applications, other solutions are available.

The standard connection joint type is not limited to use with square profiles either.  It can be used to join rectangular profiles to square profiles as well as rectangular profiles to rectangular profiles.

Probably the only drawback of this simple joint is that it is not readily re-located along the second profile piece should the need arise.  Another hole needs to be drilled to suit the hex key at the desired new location.  Admittedly, this situation doesn’t often crop up, but it does occasionally.  For details of one of many alternative solutions, see this blog post; what are clamping plates.

Full Body Joint

One variation of the standard connection is known as a full body joint.  A full body joint can be used where slightly heavier duty demands.  The main difference in this joint variation is that the drilled perpendicular hole is to suit the fixing screw rather than the hex key.  This adds a small amount of complexity, and hence time, to preparing the joint, but it remains a very cost effective joint.

T-Slot extruded aluminium profile joints - Standard connection - aluminium extrusion                            T-Slot extruded aluminium profile joints - Standard connection - aluminium extrusion

Diagrams from the Alusic catalogue showing two forms of a full body joint.

Joining the other size aluminium profiles

This basic type of T slot connection is not only cost effective it is also incredibly versatile. All of our profiles can be connected this way without the use of any accessories and different size profiles can be joined in this way.

Determining the deflection of a profile under load


Using the information supplied in the catalogue you can calculate the amount of deflection you can expect to get when applying a specific load to a specified span of profile.


Engineering Calculations Load - Deflection Chart



Using this diagram we can work out how much a given profile is expected to deflect under a given load condition. The example shown here is for an 800mm long section of profile with a moment of inertia of 10cm^4 and an applied load of 3000N.

Please note that the moment of inertia, Ix & Iy, of each profile is included in the Alusic catalogue along with other information such as section modulus and mass per metre.

Starting along the bottom of the chart, find the length of the profile, in this example the blue vertical line at 800mm. On the left side of the chart find the applied force, in this example the blue horizontal line at 3000N.

Now, from the intersection of the horizontal and vertical lines, draw an oblique parallel line. Then, on the right side of the chart find the moment of inertia of the profile, in this example the blue horizontal line at 10cm^4. Where this horizontal line intersects with the drawn oblique line, draw a vertical line up through the deflection bars above the chart.

The expected maximum deflection of the length of profile can now be read directly from the deflection bar for each of the three figured load cases; cantilever, pinned supports, fixed supports. In this example the expected deflection would be 73mm, 4.7mm, or 1.4mm respectively.

The Load-Deflection diagram we are using here can be found in the Alusic catalogue. The catalogue is available as a FREE download from our web site. Please be aware that this is an 88MB, 796 page PDF file

Obligatory caveat.

This example provides only a general indication. The exact dimensions of, and loads on, each structure must be calculated by the customer separately from this example.

Technical Specifications of T-Slot Aluminium Profile

Extruded Aluminium T slot profiles

Our extruded T slot Aluminium profiles generally come in one of the 3 standard slots as shown below. Please contact us if you need more information

6mm Slot – 30 & 60 Series

Detail of 6mm slot in 30 series extrusions

8mm Slot – 40 & 80 Series

Detail of 8mm slot in 40 series extrusions

8mm Slot – 45 & 90 Series

Detail of 8mm slot in 45 series extrusions

Technical Data for Alusic Aluminium Profile

All extruded aluminium profiles are manufactured by Alusic SRL (Italy) using a primary aluminium alloy EN-AW 6060 (Al Mg Si  0.5).  The metallurgical state of the extruded aluminium bars is T5/T6 (solution heat treatment, tempered and artificially aged) to ensure long lasting dimensional and mechanical property stability.

The dimensional tolerances for aluminium profile extrusion are in compliance with the European standard UNI-EN 12020-2 for precision extrusions.

Chemical composition of alloys:

 Alloy  Cu  Fe  Mn  Mg  Si  Zn  Cr  Ti  Al
 6060  0.10  0.1–0.3  0.10  0.35–0.6  0.3–0.6  0.15  0.05  0.10  Rest
 6063  0.10  0.35  0.10  0.45–0.9  0.2–0.6  0.10  0.10  0.10  Rest

The mechanical properties after heat treatment:

 Alloy Maximum Stress
(N / mm2)
Yield Stress
(N / mm2)
 6060 190 150  8 70
 6063 215  170  8 75

Characteristics for the design of aluminium structures:

Elastic (Young’s) modulus 69000 N/ mm2
Electrical resistivity 0.033 Ω mm2/ m
Thermal conductivity 210 W/ mK
Melting temperature 615 – 655 oC
Thermal expansion coefficient 25 x 10-6 K-1

In addition to a guarantee of high quality and dependability of aluminium products, ALUSIC is also certified to comply with the international standard for quality assurance ISO 9001:2000.

Further information, including R&D advice can be obtained in collaboration with Profilium and Alusic’s technical and commercial departments.  Please contact us for more information.

Need more information?

If you want more information on how to use our profiles, the benefits of using the Alusic profile system or you simply want a brochure or catalogue, then go to the downloads page.

Alusic aluminium profile and accessories – faster, more cost effective assembly


A simple, yet strong joint can be achieved by using both
a socket head screw, with a square washer, screwed into theCONNECTION.JPG core hole of the profile (see image on right).  A small pilot hole is drilled opposite where the joining profile is to be located.  This is the access for a hex key to tighten the screw. 

This is the standard joint for the Alusic range and is a very cost effective outcome.  ⇒ The cost per Alusic connection as shown is $0.34 using an M8x20 bolt (084.301.003) and 13×13 washer (084.303.001).
⇒ Achieves an extremely simple, yet strong connection in under a minute.

A leading competitor’s equivalent connection costs $3.35 each and takes about 3 times longer to achieve.  In some applications you may also add our anti twist device that replaces the square washer in the standard connection.  The twin tabs on the anti twist device go into the slots of the connecting profile to prevent the joint twisting – a simple and effective solution.


The total time taken to complete a standard Competitor’s connection is 2-3 minutes depending on available tooling; with the cost of the competitor’s connection being up to 300% greater in labour costs alone, let alone the higher material cost of the connectors. 

With a competitors connection, the distance from the profile end to the centre of the cross bush, is critical to ensure the connector works effectively.  If this is not achieved accurately this length of profile is left unusable.  Whereas, with the Alusic connection system the pilot hole is simply re-drilled and the adjoining profile tapped accordingly.


The distance of the pilot hole with Alusic profile is predetermined by the drilling jig with several millimetres of adjustment from side to side.  With the Alusic connecting system there is also the option of self tapping the screw into the adjoining profile as opposed to pre-tapping to ensure the connector has the best possible fit and to eliminate any possibility of vibration affecting the joint.  The potential for a loose join can also be eliminated with the use of thread locking products like LocTite although this very rarely needed as the connection is extremely effective without this process.


To demonstrate some of the labour savings that can be achieved using the Alusic system a cost comparison exercise was undertaken on the structure shown above.  The resulting time and motion study estimated the labour saving that could be achieved using the Alusic aluminium system when compared with another high quality European competitor’s profile.

There are 350 individual connection points on this frame with a saving of between 300% to 500% in labour costs using Alusic standard connectors.  In other words, if using a competitor’s connector that takes up to 3 minutes per connection point, you would require 1,050 minutes or 17.5 hours just to complete the connections on this structure and cost it would cost $1,172.50* for the connectors. 

Using the Alusic connector it takes less than 1 minute per connection point, and you would complete the connections in 5.8 hours and it would only cost $119.00* for the connectors! That is 3 times faster than the competitor and an enormous cost saving in labour costs alone. That is a saving of 11.7 hours per structure and $1053.50* in parts!!