316 (A4) · Class 5
Square Nut
Square nuts with four flats, for cup head bolts, slots and restoration work where the nut must not turn.
About the Square Nut
Square nuts do the job of a hex nut with four flats, so a flat side can sit against an edge or in a slot and not turn while you tighten the bolt, and they suit cup head (coach) bolts and restoration work. They are made to DIN 557 in metric coarse thread, hot dip galvanised class 5 from M6 to M24, or 316 stainless in M10, M12 and M16. Choose the finish and size above; the guide below covers which finish suits indoor, outdoor and coastal work and which bolts they fit.
Also called square head nuts or DIN 557 nuts.
Features
- Four-sided square body
- DIN 557 specification
- Hot dip galvanised or 316 stainless
- Larger bearing surface
Applications
- Cup head (coach) bolts
- Restoration work where the original nuts were square
- Fixing in a slot or against an edge so the nut does not turn
- Coastal and corrosive sites (316)
What square nuts are for
A square nut does the same job as a hex nut, with four flats instead of six. Ours are made to DIN 557. The square shape gives a broad face against the work, and a flat side can sit against an edge or in a slot so the nut does not turn while you tighten the bolt from the other side.
Square nuts can be used on cup head (coach) bolts, and in restoration work where the original nuts were square. Match the thread: an M12 square nut fits an M12 coarse thread bolt or threaded rod.
Square nut sizes and packs
Every square nut we carry. Select a size to open the galvanised nut in the selector; where we carry 316, switch the finish there.
Square nuts to DIN 557, metric coarse thread, smallest to largest. Pitch in mm from the thread. A pack entry means we carry that finish in that size; the figure is the smallest quantity we sell. Tap a number to show it in the selector above.
How to choose: thread, strength and finish
- Thread: the nut size matches the bolt (M10 nut for an M10 bolt). All of ours are metric coarse thread.
- Strength: the galvanised nuts are class 5. Hobson's commercial bolt and nut assemblies pair class 4.6 bolts with class 5 nuts, so these suit commercial (4.6) bolts and cup head bolts. Hobson publishes no proof load figures for the square nuts themselves.
- Finish: match the bolt and the exposure (see below), so the nut does not corrode before the bolt.
Galvanised or 316 stainless: where each suits
- Hot dip galvanised: a 50 micron zinc coating that Hobson recommends for long term outdoor use. Hobson's corrosion guide lists hot dip galvanising or 304 or 316 stainless for anything exposed to the weather, such as decks, pergolas and open sub-floors (stainless only in the sea spray zone). Newer galvanised parts can look a duller grey than older stock; Hobson notes the brightness has no effect on corrosion resistance.
- 316 stainless: for the sea spray zone, where the corrosion guide calls for stainless, and within 2m of a pool edge, where it calls for 316. Neither 304 nor 316 is made to sit in seawater.
- Stainless threads can gall (lock up) as they are tightened. Hobson suggests driving at a slower speed and lubricating the threads with a molybdenum disulphide based lubricant. The stainless steel article Hobson publishes says swapping grades (such as a 316 nut on a 304 bolt) is not a reliable fix: galling is worse with fine threads, tight clearances, poor thread profiles, no lubrication, dirt and over-tightening.
Fitting a square nut
- Fit a washer under the nut where it bears on timber; a square washer spreads the load over a bigger area.
- Run the nut on by hand to check the thread, then hold it with a spanner or let a flat bear against an edge while you turn the bolt.
- Tighten firmly without crushing the timber. For stainless, drive slowly and lubricate the thread.
Square nuts in Adelaide
Allmat supplies square nuts, bolts, washers and threaded rod to builders, fencers, farmers and trade across Adelaide and South Australia. Add the nuts to a quote with the bolts and washers they go on, and we will price the lot.
Square nuts, bolts and washers for the job
Galvanised and 316 stainless square nuts, with the bolts, washers and threaded rod they go on, are available to order from Allmat for builders, fencers, farmers, fabricators and trade across Adelaide and South Australia. Order through Allmat, we pick and pack it, then click and collect from the Allmat yard or have it delivered to site.
Goes with
Questions
Why use a square nut instead of a hex nut?
A square nut has a broad face against the work, and a flat side can sit against an edge or in a slot so it does not spin while you tighten the bolt. It also suits restoration work where the original nuts were square, and can be used on cup head bolts.
What sizes do square nuts come in?
We carry hot dip galvanised class 5 square nuts in M6, M8, M10, M12, M16, M20 and M24, and 316 stainless in M10, M12 and M16, all metric coarse thread to DIN 557.
Are galvanised square nuts suitable outdoors?
Yes. Hobson recommends hot dip galvanised for long term outdoor use, and its corrosion guide lists hot dip galvanising or stainless for parts exposed to the weather. Use 316 stainless in the sea spray zone and within 2m of a pool.
What bolts do class 5 square nuts go with?
Commercial class 4.6 bolts and cup head bolts in the same thread and finish. Hobson pairs class 4.6 bolts with class 5 nuts in its commercial assemblies.
How are square nuts sold?
In packs: 100 for M6 to M12, 50 for M16 and M20, and 25 for M24 in galvanised; 100 for M10 and M12 and 50 for M16 in 316 stainless.
Where can I buy square nuts in Adelaide?
Order through Allmat. Order ahead by phone on 1300 03 03 63 or send your list for a quote, then click and collect from 25 Kapara Road, Gillman, or have them delivered to site.
Square Nut: sizes and finishes we supply
10 lines by finish. Pick one above for its product code and pack sizes.
| Finish | Sizes | Lines |
|---|---|---|
| Galvanised | M6, M8, M10, M12, M16, M20, M24 | 7 |
| 316 Stainless | M10, M12, M16 | 3 |
Data sheets and documents
The documents for the product you choose are listed with the selector above. Here is every Square Nut document from Hobson Engineering.
All Square Nut documents (7)
Data sheets and technical data (2)
Did You Know flyers (1)
Need them in bulk?
Add the sizes you need to your quote, or send us your list and we’ll price the lot and supply it with the rest of your order.
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