304 Stainless Steel Coupling Nuts, M2 to M24 — Any Length From 10 to 100 mm, From One Piece

Need a stainless steel coupling nut in a length or size the catalogue does not carry? Catalogue nuts are 304 or A2 at three diameters long, M5 to M20, and stop there. We cut 304 hex coupling nuts from M2 to M24 at any length, two threads of your choosing, across-flats to your spanner, from one piece. No drawing needed: a photo with a rule, the measurements in a message, the old part or its part number is enough; we draw it, you approve, we machine. Get a quote →

A 304 coupling nut we drew and made: M10×1.5, 60 mm, 17 A/F, 200 pieces for pump pipework in Italy

EKINSUN LTD is a custom parts manufacturer that cuts coupling nuts from hex bar to the thread, length and across-flats you specify, from one piece. The drawing below is our own: a long hex coupling nut, M10×1.5 through thread, 60 mm long against the 30 mm that DIN 6334 gives M10, 17 mm across flats, both ends chamfered 0.5×45°, AISI 304, natural finish with no plating. The order was 200 pieces for a customer in Italy, used in the pipework of a transfer pump, where a 30 mm catalogue nut would not have bridged the gap between the two threaded ends. The photo is one of the finished nuts being checked with an M10 6H go/no-go plug gauge before packing.

Feature	As drawn and made
Thread	M10×1.5-6H through, both ends the same
Length	60 mm, twice the DIN 6334 standard of 30 mm
Across flats	SW17, the DIN 934 nut size for M10, so any 17 mm spanner fits
Ends	0.5×45° chamfer both ends, deburred
Material	AISI 304 stainless, natural, no zinc plating
Check	Go/no-go plug gauge on the thread, dial caliper on the across-flats
Quantity and use	200 pieces, shipped to Italy, pipework of a transfer pump

Coupling nut, extension nut, long nut, connector nut, female standoff: one part, many names

The part is a length of hex bar drilled through and tapped. What it is called depends on the trade: a coupling nut or connecting nut when it joins two threaded rods, an extension nut or long nut when it lengthens one, a hex connector nut or threaded sleeve in electrical and lighting work, a female-to-female standoff or spacer nut in enclosures and electronics, a reducing nut or adapter nut when the two ends differ. In German it is a Verbindungsmutter or Langmutter, in French a manchon taraudé. Whatever it is called on your side, the callout is the same four things: thread, length, across-flats, material.

M2 to M24: what the shelf has, and what we cut

DIN 6334 defines hex coupling nuts from M5 up, always three diameters long. Below M5 there is no standard; the electronics trade sells female hex standoffs in fixed length steps. The table gives the across-flats we use by default, the standard length where one exists, and the length range we cut.

Thread	Coarse pitch	Across flats	DIN 6334 length (3d)	Length we cut	On the shelf?
M2	0.4	4 mm (ISO 4032 nut flats)	—	10–100 mm, any value	No coupling-nut standard; fixed-step standoffs only
M2.5	0.45	5 mm (ISO 4032 nut flats)	—	10–100 mm, any value	No coupling-nut standard; fixed-step standoffs only
M3	0.5	5.5 mm (ISO 4032 nut flats)	—	10–100 mm, any value	No coupling-nut standard; fixed-step standoffs only
M4	0.7	7 mm (ISO 4032 nut flats)	—	10–100 mm, any value	No coupling-nut standard; fixed-step standoffs only
M5	0.8	8 mm	15 mm	10–100 mm, any value	DIN 6334 A2 nut, 15 mm long, at most suppliers
M6	1	10 mm	18 mm	10–100 mm, any value	DIN 6334 A2 nut, 18 mm long, at most suppliers
M8	1.25	13 mm	24 mm	10–100 mm, any value	DIN 6334 A2 nut, 24 mm long, at most suppliers
M10	1.5	17 mm	30 mm	10–100 mm, any value	DIN 6334 A2 nut, 30 mm long, at most suppliers
M12	1.75	19 mm	36 mm	10–100 mm, any value	DIN 6334 A2 nut, 36 mm long, at most suppliers
M14	2	22 mm	42 mm	10–100 mm, any value	DIN 6334 A2 nut, 42 mm, from some suppliers
M16	2	24 mm	48 mm	10–100 mm, any value	DIN 6334 A2 nut, 48 mm long, at most suppliers
M18	2.5	27 mm	54 mm	10–100 mm, any value	DIN 6334 A2 nut, 54 mm, from some suppliers
M20	2.5	30 mm	60 mm	10–100 mm, any value	DIN 6334 A2 nut, 60 mm long, at most suppliers
M22	2.5	32 mm	66 mm	10–100 mm, any value	DIN 6334 A2 nut, 66 mm, from some suppliers
M24	3	36 mm	72 mm	10–100 mm, any value	DIN 6334 A2 nut, 72 mm, from some suppliers

What buyers ask for, and what we do about it

The situation	What we make	Details that go on the drawing
The same nut but longer	Any overall length from 10 mm to 100 mm	Length; whether the thread runs through or stops short of the middle
The same nut but in stainless	304 by default, 316 for chlorides, 303 for frequent assembly	Grade and finish: natural, passivated, or electropolished
Two different threads, one nut	Reducing coupling nut, M8 one end and M6 the other, or M10 to 3/8-16	Both callouts and which end is which; see the reducing-nut page for wall limits
A spanner size I already own	Across-flats to your spanner, not to the table	Flats and the largest thread that still leaves wall
I have to see the rod reach the middle	Sight hole drilled at mid-length	Hole diameter; both sides or one
One end must be closed	Blind one end, tapped from the other	Bottom thickness and the usable thread depth
Nothing to put a spanner on	Cross-drilled for a tommy bar, or knurled round body	Bar diameter or knurl pattern
I only have the old nut or a photo	Made from the sample or from measurements	Send it; the drawing comes back for approval before machining

304 first, then 316, 303, brass, steel

Material	When it is the right choice	Note
304 stainless (1.4301, A2)	Indoor, dry, fresh water, food and pharma frames	The default; natural or passivated
316 stainless (1.4404, A4)	Marine, coastal, pools, process chemicals	Chloride resistance; slightly higher cost
303 stainless (1.4305)	Nuts run on and off stainless rod repeatedly	Free-machining; galls less than 304 on 304
Brass CW614N (C360)	Water, gas and low-voltage electrical fittings	See the brass coupling nut page
Zinc-plated steel	Dry structural and general use	Stocked at DIN 6334 sizes; see the stock page
Aluminium 6061 / 7075	Enclosures and weight-critical standoffs	Anodised on request

How each nut is checked

The thread is gauged go/no-go with the plug gauge for its size and class, 6H unless you specify otherwise; the go end must run the full length, the no-go end must stop. Across-flats are measured with a caliper against the drawing, length likewise, and the chamfers are inspected for burrs. A material certificate ships with the parts on request.

Price, lead time, delivery

There is no list price for a machined coupling nut; a single piece starts from €65 and is quoted within 12 hours from the callout. One to a few dozen pieces ship in 5 working days, 50 to 500 in 15 working days, delivered DDP to your door with duties in the quote. The first piece is the sample; repeat orders run to the same drawing, and 500-piece and 1,000-piece runs are priced lower per piece. Bar is 304 (1.4301) unless the order says 316 (1.4404), 303 (1.4305), brass CW614N, zinc-plated steel or aluminium 6061; the grade goes on the drawing and the certificate.

Where the coupling nut catalogue stops

What you need	In the catalogue?	What to do
M6 to M20 A2 coupling nut, DIN 6334 length	Yes	Buy it there, or ask us — we may have it in stock
M10 coupling nut, 60 mm long, 304	No	Cut to order; the part drawn above
M2, M2.5, M3 stainless coupling nut in a length the standoff catalogue skips	No	Cut to order with ISO 4032 flats or yours
M22 or M24 stainless coupling nut	Rare	Cut to order; hex bar 32 or 36 mm
Two different threads in one 304 nut	No	Reducing coupling nut, MOQ 1
Sight hole, blind end, cross-drilled or knurled body	No	Drilled or turned to your drawing
Across-flats that is not the table value	No	Cut to the spanner you have
316 instead of 304 at any of the above	Rare	Same job, different bar

Related coupling nut pages

Frequently asked

Can you make a 304 coupling nut longer than the catalogue size?

Yes. A catalogue coupling nut is three diameters long because DIN 6334 says so: M10 is 30 mm. Ours is a length setting on the saw and the lathe, so an M10 nut at 60 mm, an M6 at 100 mm or an M20 at 45 mm is the same job; we cut from 10 mm to 100 mm overall. The drawing above is an M10×1.5 nut at 60 mm, 17 mm across flats, in 304.

Can I get only one made, or five?

Yes. Minimum order is one piece; a single 304 coupling nut starts from €65 and ten pieces share the same setup. The M10×60 nut on this drawing ran as 200 pieces for pump pipework in Italy; one piece or two hundred is the same drawing. Ask for the quantity you need, not a box.

Which thread sizes can you cut?

M2, M2.5, M3, M4, M5, M6, M8, M10, M12, M14, M16, M18, M20, M22 and M24, coarse or fine pitch, and the inch equivalents from 4-40 to 1 in. Below M5 there is no coupling-nut standard at all, so those sizes are cut to the ISO 4032 across-flats or to your drawing.

Is 304 the right stainless, or do I need 316?

304 (1.4301, A2) covers indoor, dry and fresh-water service and is the default. 316 (1.4404, A4) is for chlorides: marine, coastal, pool and process chemicals. 303 is chosen when the nut will be run on and off a stainless rod often, because it galls less. Tell us where the nut lives and we pick the grade with you.

Will an M10 coupling nut fit my M10 rod?

Only if the pitches match. M10 coarse is 1.5 mm; M10×1.25 and M10×1 fine threads exist and look the same in the hand. Ten threads on the rod measure 15, 12.5 or 10 mm. Every female thread we cut is gauged go/no-go, as in the photo, so the nut runs on if the callout is right.

How do I order a coupling nut without a drawing?

Write the thread, the length, the across-flats and the material: M10×1.5, 60 long, 17 A/F, 304. A photo of the rod or the old nut is enough if any of those is unknown. The drawing comes back with the quote within 12 hours and machining starts after you approve it.