Coupling Nuts in Stock — M4 to M24, Hex & Round

EKINSUN LTD is a make-to-order parts manufacturer — nearly everything we ship is machined against a drawing or a sample. Coupling nuts are the one family we also keep on the shelf, because our own work consumes them: M4×12 to M24×70, hex and round, zinc-plated steel, ready to go. Send diameter × length and quantity — priced reply within 12 hours. And when the size you need is not on the shelf, it does not become a dead end: it becomes a machined coupling nut, from 1 piece.

How a coupling-nut callout reads

Stock references are written thread × across flats × length — the worked example above is thread M10, flats 17 mm, 60 mm overall. Every reference on this page shares the same attribute card, and it is the format to copy into an enquiry:

Attribute	Stocked value
Diameter (thread)	M4 · M5 · M6 · M7 · M8 · M9 · M10 · M11 · M12 · M14 · M16 · M18 · M20 · M24
Length	20 · 25 · 30 · 35 · 40 · 50 · 60 · 70 mm — short lengths from 12 mm on small diameters (e.g. M4×12)
Body	Hex (wrench flats) or round (cylindrical)
Thread	Metric, standard pitch, tapped through
Material	Carbon steel
Surface finish	Zinc plated, clear (white zinc)
Example callout	M10×17×60 — thread M10, across flats 17 mm, length 60 mm

What is on the shelf, diameter by diameter

Across-flats follow the usual DIN series — the same flats a DIN 6334 nut of that diameter carries — and are confirmed on every quote:

Diameter	Across flats	Lengths in stock (mm)
M4	7	12 · 20 · 25 · 30 · 35 · 40 · 50 · 60 · 70
M5	8	20 · 25 · 30 · 35 · 40 · 50 · 60 · 70
M6	10	20 · 25 · 30 · 35 · 40 · 50 · 60 · 70
M7 — rarely shelved	11	20 · 25 · 30 · 35 · 40 · 50 · 60 · 70
M8	13	20 · 25 · 30 · 35 · 40 · 50 · 60 · 70
M9 — rarely shelved	on quote	20 · 25 · 30 · 35 · 40 · 50 · 60 · 70
M10	17	20 · 25 · 30 · 35 · 40 · 50 · 60 · 70
M11 — rarely shelved	on quote	20 · 25 · 30 · 35 · 40 · 50 · 60 · 70
M12	19	20 · 25 · 30 · 35 · 40 · 50 · 60 · 70
M14	22	20 · 25 · 30 · 35 · 40 · 50 · 60 · 70
M16	24	20 · 25 · 30 · 35 · 40 · 50 · 60 · 70
M18	27	20 · 25 · 30 · 35 · 40 · 50 · 60 · 70
M20	30	20 · 25 · 30 · 35 · 40 · 50 · 60 · 70
M24	36	20 · 25 · 30 · 35 · 40 · 50 · 60 · 70

Every hex reference, written out

Round-body coupling nuts — same grid

Round (cylindrical) coupling nuts share the shelf in the same combinations: M4 through M24, lengths 20 to 70 mm, zinc-plated steel, tapped through. Body outside diameter is confirmed on the quote.

What this shelf saves you from chasing

Your need	At the trade counter	Here
One standard M10×30 (3×d, DIN 6334)	stocked — for one piece, buy it off the shelf, it is cheaper there	this shelf earns its keep on the rows below
Lengths 50, 60, 70 mm — past the 3×d catalogue cut	thin, often special order	in stock up to M24×70
Odd diameters M7, M9, M11	special order	in stock, 20–70 mm
100–500 pieces of one reference	blister packs of a few	tiers 100 / 250 / 500, priced within 12 h
Several references at once	separate orders	one grouped parcel — freight shared across the lot
Inch threads, stainless 316L (1.4404) or 303 (1.4305), brass, aluminium 6061, fine pitch, 80 mm and up	not shelved	machined from 1 piece — see custom coupling nuts

Where the shelf ends, machining begins

Stainless, a length other than three diameters, or a size outside M4–M24 is machined rather than picked: the 304 stainless coupling nuts page covers M2 to M24 at 10 to 100 mm, and the coupling nut size chart gives the across-flats, standard lengths and turns of thread by size.

The shelf covers one well-worn corner of the map — metric, standard pitch, zinc-plated steel, 12 to 70 mm. Everything beyond it is our actual trade, machined to order from one piece: reducing coupling nuts that join two different threads, metric-to-imperial transitions like M12 to 1/2-13, left-hand/right-hand turnbuckle nuts, stainless or brass bodies, special flats, sight holes — and beyond nuts, custom fasteners of every description and parts remade from a worn sample. A drawing is welcome but not required: a dimensioned sketch or a photo with calipers in frame is enough to quote.

In brass the shelf is thinner still. A brass DIN 6334 above M12 usually does not exist at all, and the inch sizes — 8-32, 10-24, 1/4-20, 5/16-18, 5/16-24, 3/8-16, 1/2-13 — come only at whatever length their maker settled on. Those are brass coupling nuts cut from hex bar, where the body length and the across-flats are yours to name.

Past 70 mm the part stops being a nut and becomes a rod: a round or hex bar tapped at both ends with a solid middle, or tapped right through, with a different thread at each end if the job needs it. Those are internally threaded rods made to length, with the tap drill, thread depth and rod diameter for each size.

Will it fit — and what if yours is one detail off

Every nut on this shelf is tapped to the standard coarse metric pitch: M6×1, M8×1.25, M10×1.5, M12×1.75, M16×2, M20×2.5, M24×3. An M10 shelf nut will not thread onto an M10×1.25 fine-pitch stud, and an M12 nut will not take a 1/2-13 UNC rod — 12.7 mm outside diameter and a 60° thread at 13 TPI, close enough to start and then bind. If your rod or stud is a fine pitch, an inch size or left-hand, it is a machined nut, not a shelf nut; tell us the pitch and it is quoted within 12 hours.

Same nut, one detail changed, is the everyday enquiry here: M10×60 but 80 mm long, M12×19×50 but in 316L, M16 hex but with a sight hole, M8 with a left-hand thread at one end for a turnbuckle. Each of those is machined from one piece of hex or round bar to the shelf nut's across-flats, so it drops into the same spanner and the same assembly. Send the shelf reference plus the one line that differs — length, material, pitch or hand — and the quote comes back within 12 hours with the price at 1, 100 and 500 pieces.

Where these nuts work

A coupling nut does two jobs: joining — two rods end to end in one line — and take-up — a long engagement to set a height or absorb an adjustment. It is the quiet part inside adjustable machine feet, ceiling-hung cable tray and workbench frames; when it is missing, the whole assembly waits for it.

How to ask for a price

Use the form on this page or write to [email protected]. Three lines cover it:

• The reference — diameter × length (e.g. M10×60), and the body: hex or round
• The quantity — single pieces, or tiers of 100 / 250 / 500 for stepped pricing
• Any other references on your list — one grouped parcel beats several small ones on freight

A firm price comes back within 12 hours. If your size is not in the tables above, the same enquiry simply becomes a machining enquiry — length, thread, flats and material all free — answered just as fast via custom coupling nuts.

Frequently asked questions