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.
Related: Bondhus T-Handle Ball Hex Drivers Review
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.
Additional Sources: McMaster | Zoro
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
Thank you, Ben ,for a very informative post. I will definitely bookmark this. Nice workshop too in your last post!
Love the cutting fluid recommendation! Oh. And your well paced story too.
Thumbs up x2, for the fast response with these details!
Gives a better understanding and visual confirmation of how thing fit together, as I have not yet worked with it.
You’re welcome, thanks for the feedback.
For visible corner joints I generally use these as they are the nicest looking solution:
I haven’t used these, but they will give you a clean mitered outside corner as well:
Glad you put this together – and outlined some options.
It is costly but like you say money for speed of build.
Being in aviation I have some appreciation for the AL.
(I haven’t looked but I assume you could anodized it I would have to have some green in there)
IIRC, most aluminum framing is clear anodized.
Quick story: many years ago, a customer insisted that we use aluminum framing for a machine (I guess to match the other machines on that production line). But it needed to be ESD safe, and anodized aluminum isn’t (for ESD safe, the framing needed to be conductive or dissipative, but the anodized layer is an insulator).
So all the framing (Parker Parframe) was shipped out to get stripped, and then electroless nickel plated, at substantial expense. After all of that, a welded steel frame would’ve been less expensive but much more rigid.
For a large enough order, I’m sure that framing can be ordered without anodizing.
While not relevant to ESD-safe requirements, there’s an interesting anodize breaker accessory that helps create a grounding pathway across mated profiles.
It wasn’t a large enough order (only one machine), and I’m not sure how big an order would have to be. For example, only one company, Banner Engineering, makes ESD safe light curtains. Changes include electroless nickel instead of paint or anodizing, and ESD safe plastic for the optical window.
Another tip I remembered when working with extrusions like this is to use thread forming taps. No chips, and you can run them in with a cordless drill without issue as long as you drill the correct thread forming tap size hole (the hole will be bigger than for a standard tap).
These extrusions tend to be pretty gummy, which can make it easy to break taps. I usually cheat up the hole size a bit as well, because thread pull out is rarely an issue.
I might try that one day. Cutting threads into the center hole is easy enough with spiral taps, but cleaning the chips out can be a pain. Do you have any particular brand recommendations?
Balax is one of the bigger names.
There is a drill chart in the link, 65% thread engagement is fine for most applications if you have more than 3 threads of engagement. Hole size is very important with these, so buy a few matching tap drills at the same time.
The only other trick with these is you need to countersink the hole just larger than the major thread diameter. Otherwise the first thread is funky.
Oh and just for fun while we are discussing taps:
High speed rigid tapping on a Brother Speedio
T-slot aluminum has pre-formed center holes. You can enlarge them a little, but it can be hard to center the existing hole. There’s no way to make the hole any smaller in case a smaller hole size is recommended.
A form tap will always use a larger hole than a cutting tap. Material is pushed to fill towards the minor diameter.
The ideal approach is start with a countersink that has a wider angle than your drill point. 120 deg 6 flute MA Ford countersink:
Follow up with 118 deg. drill. The initial countersink will keep the drill centered and provide a good first thread from the form tap.
Good idea, thank you, I’ll give that a try!
Great post to go with the other one! Good to finally see how these extrusions work in detail. Excellent reference.
Agreed! I’ve never been inclined to go down this road because I don’t want to evaluate all the options for joining rails, installing hardware for drawers, doors and what not. The visuals here really made it simple. In 5 minutes I understood several options, pros and cons and some cost references. Thank you Ben!
No problem! Thanks for the feedback!
OpenBuild, DIY CNC makers, introduced slip fittings in 10 packs that may be money savers.
That looks interesting, but also potentially a lot weaker. 8020 has an internal corner bracket, and it’s not as strong as any of the methods discussed here. With these brackets, it looks like you could and should double up to have them on both sides of a joint for strength and squareness, but that closes the price gap if you’re able to use an end fastener instead.
IMHO, end fasteners are the only way to fly, simply because the other methods get eye-wateringly expensive when multiplied across a whole assembly. They can also be incredibly fast to make:
Get a spiral-tap and chuck it into a drill. With cutting fluid, you can tap a profile end in about 4 seconds. I tried spiral taps on a lark and they changed my life.
For corners, the access hole is always the same distance from the end of the piece. Skip the (again needlessly expensive) drilling jig from 8020, and just set up some blocks on your drill press. You can make this hole in seconds for free.
The end-fastener clip thingy is also probably not necessary. Just hold the pieces flat (clamp ’em?) while tightening the fastener. Once it’s torqued down, it’s unlikely to rotate. If you’re really worried about rotation, you can also plan your corner overlaps to lock certain members against others.
With this, your cost per joint is down to a single screw, and time is probably 20 seconds all-in. Build everything cheaper and faster!
excellent, cleared up any questions I had from the other post, as the old song goes, Now I see clearly
The photo of the End Fastener joint isn’t assembled correctly. The flat part of the bracket should be inside the T-slot and under the head of the fastener like a washer and the “wings” should engage the slots on the piece with the tapped threads to prevent rotation. Perhaps this is because of the flanged head screws you used, I’ve never tried that combination.
One other distinction between the end fasteners and the others options is adjustability, you can’t move a joint with an end fastener unless you drill another access hole for the wrench.
Oh well spotted! I purchased four and only used them to take this photo!
This article is why I love this website so much, thank you!
which one is the strongest?
I believe anchors.
Agreed, that’s my understand to.
I checked their catalog and they have load ratings for the extrusions but not for the brackets.
I’ve been curious about this material and you’ve provided some well-written insights.
Would a capable welder be able to do what this system does?
Keep up the great work Team TG!
In terms of functionality, yes. In terms of reusability and easiness, no.
I’m in the process of rebuilding my Router table and it would have been way harder if I had to cut the welds and redo them. Instead I’m just moving things around, and cutting the occasional piece of aluminum. For me that’s the primary benefit, the ability to easily repurpose, especially when I stuck to a modular design that used the same pieces for every design.
Thanks for reading!
I’m a BIG fan of what you’ve done with your shop. After seeing your project, I found a large supply of used extrusion that I purchased at a great price. While the price was great, I didn’t have the luxury of deciding exact lengths, series, or pre-drilled holes. As a result, I’ve got a ton of 80/20 and now I’ve got to figure out what I’m going to make out of it.
As part of the deal, I’ve got (110) 80/20 15-series anchor fasteners. Since most of the framing extrusion will need to be cut to length, I’m going to have to countersink the holes for the anchors. I’ve got a Wen 4214 drill press that has variable speeds. I am just unsure of whether it’s capable of doing a good job on aluminum and if so, the correct bit to use.
Do you (or anyone here) have any experience countersinking holes for the anchors using a drill press or another method? I’d really prefer to not take them into a machine shop if possible. I found a pretty old YouTube video suggesting to use a chamfer bit on a drill press. Any advice would be appreciated.
In case anyone is curious, I’ve got 134 feet of 15-series mixed between 3030, 1530, 1515, and 1515 lite. I’m pretty excited to get going on this project.
That’s a really nice find!
80/20 does sell a countersink bit but it’s designed for a bore, not a drill press. I did look into buying one but I don’t know that much about them and they are not cheap!
I recommend posting a question on the forum and seeing if someone has some ideas….
Did you ever find a way to do the counterbores on the extrusions? I am searching for that as well. Thanks