In my series on building modular tool cabinets, several readers asked for more details on how the various fastener options work. In this post I’ll walk through the three most common methods and some tips I have picked up.
Anchor fasteners are the premium option for connecting T-slot aluminum extrusions. That’s not just because they are expensive, but because they are very strong and also extremely quick to use. Additionally, they do an excellent job of squaring up two pieces of aluminum.
Anchor fasteners require counterbores near the ends of T-slot aluminum, and while you could bore you own holes for the fastener I relied on Faztek to do the machining for me.
For the frame that was shown in the introductory post, there were 11 15-series members that needed 2 counterbores each (one at each end), for a total cost of $36.30, or $1.65 each.
For the fastener itself, there is kit that consists of the anchor, screw, and a drop-in T-Nut. You simply plug it in, and tighten it using a 1/4″ ball hex end driver. These are $2.33 each, so $51.26 total for my build.
I have no regrets using these as my primary way of building my cabinets.
Brackets are flat or corner extrusions with hole spacing that corresponds to the centering of T-slot extrusions.
Whilst brackets can be the most expensive method of joining extrusions together, they do provide a solution when the other options don’t work. As a result I have a healthy supply of the flat and corner brackets shown above for when I need them.
Each bracket will take two or more 5/16″-18 x 5/8″ flanged button head socket cap screws (FBHSCS) and 5/16-18 T-nuts.
Other Fasteners Options
I wanted to point out some alternative options for the screws. This is important because you’ll need a decent quantity for any build.
I initially bought Faztek’s 5/16-18 x 5/8 FBHSCS. Their flanged button head socket head cap screws are definitely high quality, and the size of the button head is notable. The extra surface area can be important for some applications, eliminating the need for a separate washer.
I have also purchased alternatives that I found on ebay. They are about 30% cheaper and I have no problem using them, despite the smaller head.
Stuart’s Note: I usually order 5/16″ screws from McMaster when I need them in a hurry, or Zoro when I have time or want USA-made Kerr Lakeside hardware. A 100-count box of Kerr Lakeside screws is currently $12.43. If you use washers, you might need slightly longer screws, but not too long because they can bottom-out in the T-slot. For filleted corner brackets, flanged button head screws don’t always sit flat for me.
End fastener require a bit of work, but they are the cheapest option. They work by fastening the end of one piece of extrusion to the side of another. To do this you need to tap a screw thread into the end of one extrusion, and drill an “access hole” so you screw it in.
You need an end fastener assembly hardware kit, costing $1.47 each. This includes the screw and an end clip that adds to the strength of the connection and helps with square alignment.
For stationary installations, such as my 3D printer cabinet (more on this in another post) I have saved some money by only using a screw. This is where Faztek’s button head screws with the larger head are preferable, but you can also just use a washer to increase the surface area. This still give you a nice rigid installation but it may not be suitable for builds that experience vibrations.
To do the installation you need a couple of tools:
- Hole tapping jig – Faztek and 80/20 sell them (or you can make your own)
- 9/32″ drill bit
- 3/16″ Hex End T-Handle Driver – I like the Bondhus ProHold
- 5/16″-18 tap – I have the Cle-Line C62160 on Amazon
- Cutting fluid, I have been amazed at the difference this stuff makes
First, you use the hole tap to create a thread for the screw.
The hole is appropriately sized throughout the length of the extrusion already, and so it’s ready to be tapped. This is also something that Faztek or 80/20 can do for a fee.
Then, you drill an access hole using the jig in the piece it will connect to.
Finally, you start the screw in the threaded hole, slide it into the T-slot of the mating extrusion, and use a hex driver to tighten the screw through the access hole.
You can attach your casters to the frame using the same 5/16″-18 x 5/8″ button head hex head screws, a locking washer, and a 5/16-18 T-nut.
The locking washer is particularly important because these fasteners do take a hammering as the casters move.
I have had no problem with my plate casters mounted to the extrusions on 3 corners. It would be ideal to have them mounted on all 4 corners, but that will require custom machining of a special intermediate component. A more robust connection would be required for heavy-duty applications.
Carriage bolts are also worth including in this discussion. A 5/16″-18 bolt can be screwed into the end of one extrusion, and the square part of the bolt can be locked into the T-slot of another 1515 series extrusion. This provides a cheap and non-permanent method of joining two pieces.
I have used them to hold a vertical pieces into a position with a horizontal piece, such as shown in the photo. You can tighten the bolt down to get the fit nice and tight, then the weight of everything above adds to the rigidity.
What you don’t want to do is put the carriage bolt in such a position where you have to choose between square alignment or full tightness. This makes them far less suitable in a horizontal orientation, although they can be used in such a manner if you have round bars that can be fully tightened.
The size of the square flats also need to be taken into consideration, since they can protrude beyond the T-slot and hamper tightening. In such a case, the connection can feel tight when it’s not, if the square shoulder reaches beyond the T-slot and touches the surface of the mating piece.
Given the endless possibilities of building with aluminum extrusions, it is only fitting that there are a variety of different ways of fixing it all together.
It can be a little overwhelming, but hopefully the choices are clearer now.
Tools and Materials
- Faztek’s 15-series Fasteners
- Faztek’s 15-Series Brackets
- Bondhus 3/16″ Hex End T-Handle Driver ProHold
- Cle-Line C62160 Plug Chamfer Spiral Point Tap, 5/16-18 UNC
- CRC 03400 16oz Truetap Cutting Fluid Heavy Duty Bottle – whatever cutting fluid you use, make sure it’s suited for aluminum