Stainless Steel Tube Fittings: Push-Fit Instead of Welding
Push-fit fittings: building a stainless steel railing without welding
A stainless steel railing consists for the most part of straight tubes and a few changes of direction. The classic answer to that is welding: tack, weld, grind, pickle, passivate, polish. Four of those six steps are rework – and they decide how the railing ends up looking.
The other answer is the push-fit fitting. The tube is cut to length, deburred, pushed into the fitting and bonded. Done. No distortion, no heat tint, no re-grinding at a spot that then looks different from the rest.
What a push-fit fitting is
A push-fit fitting is a stainless steel formed part whose inside diameter is matched precisely to the outside diameter of the tube. The tube slides in with a small clearance – a few tenths of a millimetre, exactly the range in which a retaining adhesive develops its strength. On the outside the fitting sits flush, the surface is brushed to grit 240 and therefore matches standard commercial brushed tube.
They come in every shape a railing structure needs:
- Straight connectors for extending a handrail
- Elbows 90°, tight or wide radius, for corners and turns
- End elbows that take the handrail neatly downwards or to the wall
- Tees and crosses for post connections
- Swivel fittings for stairs and ramps – infinitely adjustable
- Tube saddles and wall brackets for branches and wall fixing
- End caps for the open tube end
Why this is usually the better choice for a stainless steel railing
| Welding | Bonded push-fit fitting | |
|---|---|---|
| Tools | TIG set, shielding gas, grinder | Tube cutter, deburrer, adhesive |
| Qualification | Welder | Practical skill |
| Rework | Grinding, pickling, passivating | None |
| Appearance of the joint | Visible, has to be blended in | No visible seam |
| Corrosion protection | Locally weakened by heat, has to be restored | Remains untouched |
| On site | Power, gas cylinder, flying sparks | No problem |
| Correction possible | Only by cutting apart | Yes, before curing |
The time factor is what fabricators notice most clearly. Welding a handrail corner and blending it in visually costs – counted honestly, with grinding and passivating – a good half hour. The same corner as a push-fit fitting: cut the tube to length, deburr, degrease, apply adhesive, push home. A few minutes.
On top of that comes the point that is hard to express in figures: it simply looks good. A neatly set fitting has a clean, calm outline. A ground-back weld seam is always a compromise – you can see that something was joined there.
How the bonding is done
Anaerobic retaining adhesives are used for the tube-to-fitting joint, of the kind common in mechanical engineering for shaft-hub connections. LOCTITE 638 and LOCTITE 648 are widely used; equivalent products from other manufacturers work just as well.
- Work clean and free of grease. Degrease the tube end and the inside of the fitting with cleaner. Grease is the most common reason for a joint that does not hold.
- Use activator. Stainless steel is a passive material – anaerobic adhesives start to cure noticeably more slowly on it. The matching activator solves this and is expressly recommended by the manufacturer for stainless steel.
- Apply the adhesive thinly and all the way round, then push the tube in while turning it slightly. Turning distributes the adhesive in the gap.
- Align it while you still can. Check angle and alignment before the adhesive starts to grab.
- Let it cure. Hand-tight after minutes; these adhesives reach their final strength after about seven days. LOCTITE 638 then achieves around 28 N/mm² shear strength on stainless steel. Do not load the structure fully during this time.
- Wipe off any excess before it dries.
The permissible bond gap for these products is in the region of 0.25 mm – and that is exactly what the fit of our fittings is designed for. Follow the data sheet for your adhesive; the values differ from product to product.
304 (V2A) or 316 (V4A)?
You will find both materials with us:
- Stainless steel 304 (V2A, 1.4301, AISI 304) – the standard for interiors, houses and covered outdoor areas. Covers the vast majority of railings.
- Stainless steel 316 (V4A, 1.4401/1.4571, AISI 316) – molybdenum-alloyed and therefore considerably more resistant to chlorides. The right choice near the coast, at swimming pools, where road salt is used and in industrial atmospheres.
If in doubt, choose 316 (V4A). The extra cost is insignificant compared with the cost of putting things right later. Use the material filter in the category to filter specifically for V2A or V4A.
Sizes and wall thicknesses
A fitting has to match not only the tube diameter but also the wall thickness – because the wall thickness determines the inside diameter of the tube and therefore the fit of plugs and insert parts. So check both figures.
| Tube Ø | Usual wall thickness | Typical use |
|---|---|---|
| 21.3 mm | 2.0 mm | Infill bars, cross bars |
| 26.9 mm | 2.0 mm | Light handrails, infills |
| 33.7 mm | 2.0 / 2.6 mm | Handrails, intermediate tubes |
| 42.4 mm | 2.0 / 2.5 / 2.6 mm | Standard for handrail and post |
| 48.3 mm | 2.0 / 2.5 mm | Heavier posts, large spans |
| 60.3 mm | 2.0 mm | Special structures |
In addition, square tube connectors for 25×25, 30×30 and 40×40 mm as well as bar connectors for round bars Ø 10 to 16 mm.
When welding is still the right decision
We sell push-fit fittings – but they are not the right choice in every case. Reach for the welding set if:
- the structure has to carry high dynamic loads – industrial environments, traffic areas, guardrails with increased impact loading
- a structural calculation is required that is based on welded connections
- you need special angles for which no formed part exists
- temperatures above 100 °C act permanently on the joint – anaerobic adhesives reach their limit here
For the transition we also stock weld-on parts, so that you can combine both techniques in one structure.
What you are responsible for as the builder
A railing is a safety-relevant component. Two points need to be stated clearly:
- Sizing is up to you. Post spacing, tube cross-section, fixing into the substrate and the rail loads to be applied depend on how the building is used. In public and commercial areas this belongs in the hands of a structural engineer.
- The TÜV type test of our malleable iron range does not apply to these parts. The tested bending moments and slip resistances relate exclusively to the hot-dip galvanised tube clamp fittings in malleable cast iron. No such test values exist for the stainless steel push-fit fittings.
The load capacity of a bonded joint also depends directly on the workmanship – cleanliness, activator, curing time. Anyone who observes these three points gets a joint that has worked reliably in railing construction for years. Anyone who skips them does not.
Next
Building a stainless steel railing – step by step · See all stainless steel tube fittings
Not sure which part suits your structure? Give us a call – we will go through the parts list with you.