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12 בJuly 2026How to make a steel connection to steel?
How to Make a Steel-to-Steel Connection?
How do you connect two profiles together, and what are the advantages and disadvantages of each method? Here is a small, useful summary of all the available technologies — welding, bolt and nut, expanding anchor, powder-actuated nail, and self-drilling screw.
In short
Five standard methods connect steel to steel, each with its own trade-offs. Welding gives full capacity but demands skill, loses corrosion protection and needs costly inspection. Bolt-and-nut is easy to inspect but needs access on both sides. The Strutbolt expanding anchor solves the no-rear-access case but is expensive and slow. Powder-actuated nails are the fastest but need a costly gun. And self-drilling steel screws are the easiest, cheapest and simplest to inspect — yet are almost absent from designers’ options, mainly because of low-quality, unrated imported screws.
The available methods and technologies
1. Welding
This is a physical action based on melting one of the metal bodies, usually with the addition of further metal as a filler material. It is a very classic method, with a possible capacity identical to that of the connected steel profiles themselves.
Disadvantages of the method
- When connecting two different materials, or materials of different thickness, the welding device and filler must be matched to the materials and thicknesses. This requires a very professional worker.
- There are materials that cannot be welded.
- The welded area loses its corrosion protection and requires additional treatment (even for stainless).
- Visual inspection is only partial. Checking the connection quality requires complex, expensive tests such as magnetic-particle, ultrasonic, radiographic or penetrant testing.
- The finish is not always aesthetic and will require grinding, cleaning and smoothing of the weld bead before touching up the paint.
2. Bolt and nut
This is especially good when the holes are already prepared. If there are no ready holes, a magnetic drill must be used to drill them on site. The method is easy to apply and easy to inspect.
Disadvantages of the method
- Requires access on both sides of the connection, and a certain thickness for the bolt head and the nut.
- Drilling a thick profile takes a lot of time.
- The finish has a protruding bolt/nut head.
3. The anchor that opens behind the profile (STRUTBOLT)
A female anchor that is opened by closing a male bolt that pulls a cone nut, which opens the sides of the sleeve so they resist the anchor’s pull-out. When the holes are ready, installation is very fast and easy, even when there is no access to the other side of the connection. The capacity is well defined and the installation is very easy to inspect, with the possibility of a heavy connection at a large thickness.
Disadvantages of the method
- Drilling a thick profile takes a lot of time.
- The anchor cost is very high.
- The finish has a protruding bolt head.
4. Powder-actuated nail
This is a method of connecting two profiles with special nails fired from a cartridge or gas gun. The installation is very fast and easy, and the connection’s capacity is well defined.
Disadvantages of the method
- Requires buying a gas or cartridge gun at a high cost; the nails/cartridges/gas are also not cheap and not for all types of application — each different thickness needs a different nail and/or a different gun.
- Thick profiles require heavy tools that are not easy to use, and when installing in thin profiles it is difficult not to bend or damage them because of the firing force.
5. Self-drilling steel screws (known as “isqurit”)
This method is based on self-drilling steel screws that create a thread inside the profiles, with or without pre-drilling. The installation is very easy and requires no special equipment (apart from a fairly standard fast driver), and allows a fairly precise design of the connection’s capacity, with no need for inspection.
Disadvantages of the method
- The vast majority of steel screws in Israel are imported from China and are of very low quality, with no written capacities. This is where designers’ distrust of steel screws comes from.
- Pre-drilling is required at a total thickness above 12 mm (up to 15 mm) between two profiles.
- The screw diameter is limited (up to 6.3 mm), which means their capacity is also limited (up to about 1300 kg per screw).
Comparing the methods — a cost and time test (case study)
To understand the differences better, let us take the example of a connection between a 4 mm-thick profile and a 6 mm-thick profile. We want a connection that holds more than 12 tonnes in pull-out.
| Connection method | Estimated work time | Estimated cost | Worthwhileness & overall rating |
|---|---|---|---|
| Welding | 15–20 minutes of a professional worker (for 30% of the total length) | About 80 ₪ (filler raw material + anti-corrosion spray) | ✓ A standard choice |
| Bolt and nut | Nearly half an hour to drill (with a magnetic drill when the holes are not ready) and tighten to the required torque | About 40 ₪ (a less-skilled worker + the cost of the bolts) | ✓ A conservative alternative |
| Expanding anchor (STRUTBOLT) | About an hour (drilling 4 holes of 20 mm diameter and installing 4 M12/18 anchors) | About 150 ₪ (including the anchors — a very high cost) | ✗ Expensive and slow (but solves the lack of rear access) |
| Powder-actuated nail (cartridge gun) | The fastest in terms of time | About 50 ₪ (about 25 shots at 2 ₪ each) — conditional on a cartridge gun costing about 7,000 ₪ | ✓ Very fast |
| Self-drilling steel screws | A few minutes | 2.5 ₪ only (about 10 screws at about 0.25 ₪ each) | ★ Underrated because self-drilling screws are associated with a cheap, non-engineered product — the most efficient and cheapest solution |
The bottom line in the result test
In summary, it is hard to understand how a method that is so much easier, simpler, easier to inspect and cheaper than the others is almost absent from the table of options that designers consider — referring to the self-drilling steel screw method.
Sources
- ADIT engineering guidance on steel-to-steel connection methods (welding, bolt-and-nut, Strutbolt, powder-actuated nail, self-drilling screws).
- ADIT self-drilling screw data (capacity, pre-drilling threshold, diameter limits) and the case-study cost comparison.