Element	What the photos show	Function
Closed dome	Smooth hemispherical top, no through hole on the crown	Covers the stud end, keeps dust and water off the thread, removes the sharp exposed end
Hex body	Six flats below the dome	Standard wrench or socket drive, same handling as a hex nut
Chamfer at the dome base	A visible transition ring where the dome meets the hex	Reduces the sharp edge and evens out the polished surface
Internal thread	Coarse thread cut through the body, stopping inside the dome	Full engagement on the stud without breaking through the crown
Hex thickness	Measured as K on drawing A and h on drawing B	Determines wrench engagement height
Overall height	Measured as h on drawing A and m on drawing B	Must clear the stud projection so the dome seats fully
Polished surface	Bright, mirror-like reflections across dome and flats	Decorative finish on exposed fastening

Symbol	Drawing A label	Drawing B label	Meaning
d / D	d: Thread Inner Diameter	D	Nominal thread diameter, e.g. M6
P	Pitch P	P	Thread pitch, coarse or fine
K	k: Thickness of Hexagon	h	Height of the hex section only
h	h: Nut Thickness	m	Overall height including the dome
s	S: Width Across Flats of Hexagon	s	Distance across the flats, given as max/min on A

Nominal diameter D	Pitch P (mm)	K hex thickness (mm)	h overall height (mm)	s max (mm)	s min (mm)
M3	0.5	2.5	6.2	5.5	5.32
M4	0.7	3	7.8	7	6.78
M5	0.8	4	9.8	8	7.78
M6	1	5	11.7	10	9.78
M8	1 / 1.25	6	14.7	13	12.73
M10	1 / 1.25 / 1.75	8	17.9	17	16.73
M12	1.25 / 1.5 / 1.75	10	22	19	18.7
M14	1.5 / 2	11	24.6	22	21.67
M16	1.5 / 2	13	28	24	23.67
M20	1.5 / 2 / 2.5	16	34	30	29.16

Size	D	P	h hex thickness	m overall height	s across flats
M5-0.8 mm	M5	0.8 mm	4 mm / 0.15 in	10 mm / 0.4 in	8 mm / 0.31 in
M6-1.0 mm	M6	1.0 mm	5 mm / 0.2 in	12 mm / 0.47 in	10 mm / 0.4 in
M8-1.25 mm	M8	1.25 mm	6 mm / 0.23 in	15 mm / 0.6 in	13 mm / 0.51 in
M10-1.5 mm	M10	1.5 mm	8 mm / 0.31 in	18 mm / 0.7 in	16 mm / 0.62 in
M12-1.75 mm	M12	1.75 mm	10 mm / 0.4 in	22 mm / 0.86 in	18 mm / 0.7 in

Size	Chart A	Chart B	Observation
M5	overall h 9.8	overall m 10	0.2 mm difference, consistent with rounding
M6	overall h 11.7	overall m 12	0.3 mm difference
M8	overall h 14.7	overall m 15	0.3 mm difference
M10	s max 17	s 16	1 mm difference in across-flats
M12	s max 19	s 18	1 mm difference in across-flats

Property	304 stainless steel	316 stainless steel
Core composition	Austenitic, chromium-nickel	Austenitic, chromium-nickel with molybdenum
Corrosion resistance	Good for indoor and general outdoor exposure	Better resistance to chlorides and salt exposure
Typical environment	Indoor equipment, furniture, general assembly, dry outdoor	Marine, coastal, poolside, de-icing salt, chemical and food processing
Appearance	Polished silver, identical look to 316	Polished silver, visually near-identical to 304
Magnetic behaviour	Generally non-magnetic when annealed, slightly magnetic after cold working	Similar, generally non-magnetic when annealed
Relative cost	Lower	Higher, due to molybdenum
Practical guidance	Default choice unless chlorides are present	Choose when the part will see salt or chloride exposure

Finish	Appearance	Note
Polished, mirror	Bright reflective surface as shown	Standard look for exposed, decorative fastening
Satin / brushed	Directional, lower gloss	On request; reduces visible fingerprints
Passivated	Same appearance, cleaner surface	Removes free iron after machining; recommended after polishing
Other	Per project	Confirm with an appearance sample

Application	Why an acorn nut fits
Railing and balustrade	Covers exposed stud ends for a clean, safe finish
Marine and coastal equipment	316 body plus dome protection in salt exposure
Automotive and motorcycle trim	Decorative cover over visible studs
Furniture and fit-out	Rounded cap on through-bolts and threaded rods
Playground and guardrail hardware	Removes the sharp protruding thread end
Machinery guards and covers	Protects thread ends during washdown and handling
Signage and display structures	Visible fastener treated as a design element

Point	Guidance
Stud length	The stud must be shorter than the internal depth so the dome seats on the hex, not on the stud tip
Thread engagement	Aim for engagement across the hex height, not just a few threads
Wrench	Use a socket or wrench on the flats; do not grip the polished dome
Torque	No torque value is published in the images; set it from the stud grade and joint requirement
Protection during assembly	Tape or a soft jaw avoids marking the polished surface
Reuse	A cap nut can be reused if the thread and dome are undamaged; discard if the dome is dented or the thread is deformed

Checkpoint	What is checked	Method
Thread	Size, pitch, go/no-go, run-through to the dome	Thread gauges and matching stud
Thread depth	Enough engagement without breaking the dome	Depth gauge and section check
Across flats	s within drawing tolerance	Calliper or micrometer per batch
Hex thickness	K or h as applicable	Height gauge per batch
Overall height	h or m as applicable	Height gauge per batch
Dome	Shape, concentricity, absence of dents	Visual and sample comparison
Surface	Polish uniformity, scratches, tool marks	Visual against a sealed sample
Material	Grade confirmation	Mill certificate or in-house verification

Area	Adjustable	Buyer provides
Size	M3 to M20, plus sizes outside the chart	Size list
Thread	Coarse or fine pitch per size	Pitch requirement
Height	Hex thickness and overall height	Drawing with tolerances
Dome shape	Standard dome; other profiles on request	Drawing or sample
Material	304 or 316; other grades on request	Grade and certificate requirement
Finish	Polished, satin, passivated	Finish specification and sample
Marking	Grade stamp, logo, size marking	Artwork and marking position
Packaging	Poly bag, box, carton, bulk	Packing method and quantity
Label	Logo, size table, barcode, warning text	Artwork and label copy
Carton	Mark, packing list, carton size	Marking file and shipping data

304 316 Stainless Steel Acorn Nuts — Hex Dome Cap Nuts, M3 to M20

Structure and Design