Mushroom Head Screws Manufacturer in India

Overview

JIS Mushroom Head Screws (JIS B 1111): Manufacturer & Stockist

A mushroom head screw has a wide, low dome: about 2.3 times the thread diameter across and only 0.6 times high. It spreads the load, covers the hole and sits neatly on the surface.

Exotic Alloy manufactures mushroom head screws in Mumbai, India, for electronics, appliance, enclosure and sheet-metal builders. We stock across India and supply the Philippines, South-East Asia, the Gulf and Europe. Heads and cross recesses are cold headed and threads are rolled.

One shape, several names

JIS B 1111 calls it the cross recessed mushroom head screw; Japanese catalogues often say truss head, and the inch equivalent is the ASME truss head screw. A “mushroom head bolt” is something else: the DIN 603 carriage bolt with a square neck.

JIS B 1111 M2 to M8 Cross recess Low profile A2 & A4

Mushroom head screw at a glance

Head: Low dome, d_k ≈ 2.2–2.4 d, k ≈ 0.6 d
Standard: JIS B 1111, table JA6
Drive: Cross recess No. 1, 2 or 3
Length: From under the head
Bearing: 35–56 % more than a pan head
Related: Truss, pan, button heads

JIS B 1111 M5 × 12 mushroom head screw, drawn to scale with the standard 7.7 mm dome radius. Thread and recess shown schematically; top view of the cross recess.

Specification

Mushroom Head Screw Specification

The range we manufacture and supply.

StandardJIS B 1111:2017 table JA6 (1996 edition: annex table A4, same dimensions)

Size rangeM2, M2.5, M3, (M3.5), M4, M5, M6, M8

ThreadMetric coarse, rolled; inch truss heads to ASME B18.6.3

LengthsTo order, measured from under the head

DriveCross recess No. 1 (M2–M3), No. 2 (M3.5–M5), No. 3 (M6–M8)

VariantsSlotted, with captive washer, or as tapping screws to order

MaterialsA2 (304) and A4 (316) stainless; steel; brass

FinishPlain or passivated stainless; zinc plated or black steel; plain or nickel brass

CertificationMill certificate; EN 10204 3.1; PMI for stainless

PackingBoxes of 100 to 5,000, bulk cartons, kits

Head comparison

Mushroom vs Truss, Pan, Round & Button Heads

The widest and one of the lowest heads for its thread size.

Heads of about M5 size at the same scale. The JIS mushroom head and the ASME truss head are almost the same shape; pan and round heads are narrower and taller.

Size	Mushroom JIS JA6 d_k × k	Round JIS JA8 d_k × k	Pan ISO 7045 d_k × k	Button ISO 7380-1 d_k × k	Bearing area mushroom / pan, mm²	Mushroom vs pan
M2	4.5 × 1.2	3.5 × 1.3	4 × 1.6	–	11.4 / 8.0	+42 %
M2.5	5.7 × 1.5	4.5 × 1.7	5 × 2	–	18.9 / 13.0	+45 %
M3	6.9 × 1.9	5.5 × 2	6 × 2.4	5.7 × 1.65	28.3 / 19.2	+48 %
M3.5	8.1 × 2.2	6 × 2.3	7 × 2.7	–	39.6 / 26.5	+49 %
M4	9.4 × 2.5	7 × 2.6	8 × 3.1	7.6 × 2.2	53.5 / 34.4	+56 %
M5	11.8 × 3.1	9 × 3.4	10 × 3.8	9.5 × 2.75	85.6 / 54.8	+56 %
M6	14 × 3.7	10.5 × 4	12 × 4.6	10.5 × 3.3	119.7 / 78.9	+52 %
M8	17.8 × 4.8	14 × 5.4	16 × 6	14 × 4.4	185.2 / 137.4	+35 %

mm, maximum head diameter × nominal (JIS) or maximum (ISO) head height. Bearing area on the ISO 273 medium clearance hole, from maximum head diameters: our calculation.

Dimensions

Mushroom Head Screw Dimensions (JIS B 1111)

JIS mushroom heads from M2 to M8 at the same scale, top view with the cross recess and profile drawn with the standard dome radius R.

Size	P	d_k head dia. max / min	k head height nom (max / min)	R dome radius ≈	Cross recess No.	m recess dia. ref	Penetration max / min	r under head min	Tap drill d − P	Clearance hole ISO 273 medium
M2	0.4	4.5 / 4.1	1.2 (1.3 / 1.1)	3	1	2.2	1.01 / 0.65	0.1	1.6	2.4
M2.5	0.45	5.7 / 5.3	1.5 (1.6 / 1.4)	3.7	1	2.5	1.32 / 0.95	0.1	2.05	2.9
M3	0.5	6.9 / 6.4	1.9 (2.05 / 1.75)	4.6	1	2.9	1.72 / 1.34	0.1	2.5	3.4
M3.5 (n.p.)	0.6	8.1 / 7.6	2.2 (2.35 / 2.05)	5.4	2	4	1.83 / 1.30	0.1	2.9	3.9
M4	0.7	9.4 / 8.9	2.5 (2.65 / 2.35)	6.1	2	4.3	2.13 / 1.60	0.2	3.3	4.5
M5	0.8	11.8 / 11.2	3.1 (3.25 / 2.95)	7.7	2	5	2.83 / 2.29	0.2	4.2	5.5
M6	1	14 / 13.3	3.7 (3.9 / 3.5)	9.1	3	6.3	2.86 / 2.31	0.25	5	6.6
M8	1.25	17.8 / 17	4.8 (5 / 4.6)	11.7	3	7.8	4.36 / 3.78	0.4	6.75	9

JIS B 1111:2017 table JA6, mm; identical to the 1996 annex table A4, which also listed the non-preferred sizes M2.2 and M4.5. (n.p.) = non-preferred size. Penetration = cross recess penetration depth. Tap drill and clearance hole are standard practice for reference.

Bearing area

Why a Mushroom Head? More Bearing Area

The ring under the head carries the clamp load. On the same 5.5 mm hole, the M5 mushroom head bears on 85.6 mm², against 54.8 mm² for a pan head.

For the same clamp force, more bearing area means lower pressure under the head. That is what thin sheet, soft aluminium, plastics and painted surfaces need: less denting, less creep and less paint damage.

The wide head also covers oversized and slotted holes, so panels can be adjusted before tightening, and the low dome keeps the head clear of covers, doors and fingers.

Need	Choose
Thin sheet or plastic	Mushroom head
Slotted or oversized hole	Mushroom head (or add a washer)
Small space, standard look	Pan head
Hex key drive	Button head
Flush surface	Flat (countersunk) head

Names & inch equivalents

Mushroom, Truss or Button? The Names Explained

Name	Where you see it	What it is
Mushroom head screw	JIS B 1111; UK and Australian catalogues	Low, wide dome machine screw (this page)
Truss head screw	ASME B18.6.3; Japanese catalogues	The same shape family; see truss head screws
Button head screw	ISO 7380	Smaller dome with a hex socket; see button head screws
Mushroom head bolt	DIN 603	Carriage bolt with a square neck; see carriage bolts
Mushroom head rivet	DIN 662	A rivet, not a screw

Same proportions in metric and inch

Set side by side, the JIS mushroom head and the ASME truss head of the nearest inch size have almost the same proportions: a head 2.2 to 2.4 times the thread diameter across and about 0.6 times high. The threads are different, metric against UNC or UNF, so the screws are not interchangeable, but the look and the bearing match.

Metric JIS mushroom	d_k × k mm, max / nom	d_k / d	k / d	Nearest inch ASME truss	A × H in, max	A × H mm	A / D	H / D
M2	4.5 × 1.2	2.25	0.60	No. 2	.194 × .053	4.9 × 1.3	2.26	0.62
M2.5	5.7 × 1.5	2.28	0.60	No. 3	.226 × .061	5.7 × 1.5	2.28	0.62
M3	6.9 × 1.9	2.30	0.63	No. 4	.257 × .069	6.5 × 1.8	2.29	0.62
M3.5	8.1 × 2.2	2.31	0.63	No. 6	.321 × .086	8.2 × 2.2	2.33	0.62
M4	9.4 × 2.5	2.35	0.62	No. 8	.384 × .102	9.8 × 2.6	2.34	0.62
M5	11.8 × 3.1	2.36	0.62	No. 10	.448 × .118	11.4 × 3.0	2.36	0.62
M6	14 × 3.7	2.33	0.62	1/4″	.573 × .150	14.6 × 3.8	2.29	0.60
M8	17.8 × 4.8	2.23	0.60	5/16″	.698 × .183	17.7 × 4.6	2.23	0.59

JIS B 1111 table JA6 and ASME B18.6.3 truss heads; ratios are our calculation.

Calculator

Mushroom Head Bearing & Hole Calculator

Pick the size, enter your hole diameter and tightening torque to see the bearing area, the pressure under the head and how far the head overlaps the hole.

Screw, hole & torque

Size

Hole diameter, mm

Tightening torque, N·m

Our estimate: clamp force F = T ÷ (K × d), K = 0.2; bearing area = π/4 (d_k² − hole²) from the maximum head diameter, under-head radius ignored; pressure = F ÷ area. Overlap uses the minimum head diameter. The hole resets to the ISO 273 medium size when you change the size.

Result

85.6

mm² bearing area

11.7

MPa under the head

Clamp force (est.):1000 N

Same on a pan head:54.8 mm², 18.3 MPa

Head overlap per side:2.85 mm

Head d_k × k:11.8 × 3.1 mm

Driver / tap drill:No. 2 cross / 4.2 mm

ISO 273 medium hole:5.5 mm

Materials

Mushroom Head Screw Materials & Finishes

Material	Finish	Best for
A2 stainless (304)	Plain, passivated	Electronics, appliances, indoor and outdoor panels
A4 stainless (316)	Plain, passivated	Marine, coastal, food and chemical plant
Steel	Zinc plated, black	Enclosures, racks, furniture, general assembly
Brass	Plain, nickel plated	Electrical, decorative and non-magnetic uses

Stainless A2

304

As in the photo.

304

Stainless A4

316

Chlorides and marine air.

316

Steel

Zinc or black

Economical, plated.

1018 1022

Brass

Plain or nickel

Conductive, non-magnetic.

C26000 C36000

Manufacturing

How Our Mushroom Head Screws Are Made

1

Wire

Cold heading quality stainless, steel or brass wire, certified by heat.

2

Cold heading

The dome and cross recess formed in a two-blow header.

3

Thread rolling

Metric threads rolled to 6g.

4

Inspection

Head, recess and thread checked by gauge.

5

Finishing

Passivating, zinc, black or nickel plating.

6

Packing

Boxed and labelled with the lot number.

Applications

Where Our Mushroom Head Screws Are Used

Electronics

Chassis, PCB brackets and instrument cases.

Home appliances

Sheet-metal and plastic housings.

Racks & enclosures

Panels with slotted adjustment holes.

Electrical & solar

Junction boxes, rails and clamps.

Furniture & shop fittings

Neat heads on visible hardware.

Vehicle interiors

Trim, covers and plastic parts.

Quality & testing

Mushroom Head Screw Inspection & Certification

Check	Method	Applied to
Head diameter & height	Callipers / micrometer: d_k, k	Every lot
Cross recess	Penetration gauge	Every lot
Thread	GO / NO-GO ring gauges	Every lot
Length	Measured under the head	Every lot
Surface	Visual: cracks, burrs, head finish	Every lot
Material	PMI / chemical analysis	Stainless and brass lots

Every shipment includes

Mill certificate with heat number
Dimensional report
Lot number on every box

On request

EN 10204 3.1 certificate
Salt spray test for plated lots
RoHS declaration

FAQ

Mushroom Head Screw Questions, Answered

A mushroom head screw is a machine screw with a wide, low, domed head, about 2.3 times the thread diameter across and 0.6 times high. JIS B 1111 standardises it as the cross recessed mushroom head screw from M2 to M8; an M5 head is 11.8 mm across and 3.1 mm high.

In practice they are the same shape under different names. The JIS M5 mushroom head (11.8 × 3.1 mm) and the ASME No. 10 truss head (0.448 × 0.118 in, 11.4 × 3.0 mm) both have a head about 2.36 times the thread diameter across and 0.62 times high. Japanese catalogues often call the JIS head a truss head. The threads differ, metric against inch, so the screws are not interchangeable.

It is wider and lower. At M5 the JIS mushroom head is 11.8 × 3.1 mm against 10 × 3.8 mm for an ISO 7045 pan head, which gives about 56 % more bearing area on a 5.5 mm clearance hole (our calculation). Across M2 to M8 the gain is 35 to 56 %.

A cross recess (Phillips) driver: No. 1 for M2 to M3, No. 2 for M3.5 to M5 and No. 3 for M6 and M8, as listed in JIS B 1111. Using the right number stops the driver camming out and marking the head.

No. A mushroom head bolt usually means a DIN 603 carriage bolt: a smooth domed head with a square neck, tightened with a nut, M5 to M20. A mushroom head screw is a cross recessed machine screw turned with a screwdriver, M2 to M8 in JIS B 1111.

A button head screw to ISO 7380-1 has a hex socket and a smaller dome: 9.5 × 2.75 mm at M5. The mushroom head has a cross recess and a wider head, 11.8 × 3.1 mm, so it covers more of the part but is driven with a screwdriver rather than a hex key.

The wide, low head spreads the clamp load over thin sheet and plastic, covers oversized or slotted holes, and gives a neat, low profile on panels, enclosures, appliances and electronics.

A2 (304) and A4 (316) stainless steel, like the screws in our photo; steel, zinc plated or black; and brass. A4 suits marine and chemical environments.