Mushroom Head Semi Hollow Rivets

When a rivet needs to clamp soft materials without pulling through, the head style matters more than the shank. A round head concentrates force. A flat head can dig in. But a mushroom head semi hollow rivet – with its broad, gently radiused top – spreads the load like a built‑in washer while keeping a low, finished appearance.

Nuote Metals produces mushroom head semi hollow rivets in low‑carbon steel, stainless steel, and brass using high‑speed cold heading. The semi‑hollow cavity reduces setting force by approximately 70% compared to solid rivets, making them ideal for automated assembly and delicate materials.

Below, we give you the technical specifications first, then show two real applications where our rivets solved specific assembly problems.

Technical Parameters – What Makes This Head Different

Head Geometry

The mushroom head is wider and lower than a round head, but not as wide as a truss head. It sits in the middle – ideal for plastic, thin metal, and composite assemblies where pull‑through is a concern but a truss head would look too bulky.

Material and Finish Options

 Standard Dimensions (Steel, Shank 3–8mm)

Tolerances: Shank dia ±0.05mm, head dia ±0.15mm, head height ±0.10mm, length ±0.15mm. Custom lengths and head diameters available.

Mechanical Properties (5mm Steel Mushroom Head, Set into 2mm ABS)

Different Head Types of Rivets Nuote Metals Make

Nuote Metals make rivets with different types of head, such as flat head rivets, round head rivets, countersunk head rivets, truss head rivets, mushroom head rivets etc.

1. Flat head rivets, including flat head solid rivets, flat head semi-tubular rivets, flat head tubular rivets.

Do you want to know more about our flat head rivets? just click 

2. Round head rivets, including round head solid rivets and round head semi-tubular rivets.

Click  to know more about our round head rivets.

3. Countersunk head rivets, including countersunk head solid rivets, countersunk head semi-tubular rivets, countersunk head tubular rivets.

If you want to get more information of countersunk head rivets, please click 

4. Truss head rivets, including truss head solid rivets and truss head semi-tubular rivets.

Need more information of truss head rivets? Just click 

5. Mushroom head rivets, including mushroom head solid rivets and mushroom head semi-tubular rivets.

Click  to get more details about our mushroom head rivets.

Two Real Applications – From Casters to Chairs

1. Swivel Caster Wheel – Stem Mount (Steel, Zinc Plated)

A manufacturer of office chair casters needed to attach the wheel stem to the bracket. The original design used a solid rivet, but the high setting force deformed the swivel housing. They tried a round head semi‑hollow rivet, but the head pulled through the thin metal bracket over time.

We recommended a steel mushroom head semi hollow rivet – 6mm shank, 15mm head diameter, zinc plated. The wide mushroom head distributed the load across the bracket’s surface, preventing pull‑through. The semi‑hollow cavity reduced setting force by 70%, eliminating deformation. The zinc plating matched the existing finish. After 100,000 dynamic load cycles, no rivet had loosened or failed. The customer converted all caster models to our mushroom head rivet.

2. Folding Chair – Seat Hinge (Steel, Zinc Plated)

A manufacturer of folding chairs experienced a different problem: the round head rivet at the hinge point snagged fabric seat covers. The head height of 2.8mm (for a 5mm shank) caught on the webbing during folding. Customers complained. The manufacturer also wanted a wider head to prevent the rivet from tilting in the oversized hole.

Nuote Metals supplied a steel mushroom head semi hollow rivet – 5mm shank, 11mm head diameter, zinc plated. The head height was only 1.6mm – low enough to clear the fabric. The 11mm head bridged the sloppy hole without needing a washer. The zinc plating passed 72 hours of salt spray for indoor/outdoor use. After two production runs totaling 150,000 chairs, the customer reported zero snagging complaints and zero hinge failures.

How We Manufacture Mushroom Head Semi Hollow Rivets – Cold Heading

The mushroom head is more difficult to form than a round head because the wide, low dome requires precise metal flow. Our process:

1. Wire drawing – Incoming wire (1008 steel, 304 stainless, or C260 brass) is drawn to exact shank diameter.

2. Cut‑off – Wire is cut to blank length.

3. First blow (squaring) – The blank is centered and squared.

4. Second blow (pre‑heading) – A carbide die rough‑forms the mushroom dome.

5. Third blow (final heading) – The dome is coined to final shape and flatness.

6. Piercing – A carbide punch creates the semi‑hollow cavity.

7. Trimming (optional) – Removes flash from the head edge.

8. Tumbling – Deburrs and polishes.

9. Plating – Zinc plating applied in‑house or by certified partner.

We use carbide heading dies polished to Ra 0.1µm. The dome has a smooth, consistent radius – no flat spots or tool marks.

For Details please check the Video below:

Quality Assurance – What We Deliver

Every batch of mushroom head semi hollow rivets from Nuote Metals includes:

• Mill test certificate (material chemistry, tensile, hardness)
• Dimensional inspection report (10 pieces: head dia, head ht, shank, length, cavity depth)
• Coating thickness report (zinc plating)
• Certificate of Conformance (signed, batch‑traceable)

We are ISO 9001:2015 certified. RoHS and REACH compliance is standard.

Transparent Policies

• Samples – 20 free pieces (customer pays shipping)
• MOQ – 2,000 pieces (steel, standard sizes)
• Lead time (stock) – 5–7 business days
• Lead time (custom barrel) – 12–15 business days
• Tooling charges – None for standard mushroom head tooling (sizes 3–8mm)

Three Questions We Answer Often

Q1: The caster case used a 6mm shank with a 15mm mushroom head. That is a 2.5:1 ratio. What is the maximum head diameter you can make for a given shank?

A: For cold heading, the maximum practical head diameter is about 2.8 times the shank diameter. Beyond that, the metal cannot flow fully into the die cavity without causing folds or voids. For a 6mm shank, the largest mushroom head we can reliably produce is 17mm. For a 5mm shank, 14mm is the limit. If you need a wider head, we would recommend switching to a truss head or adding a separate washer. For the caster case, 15mm was within our capability and worked perfectly.

Q2: Can mushroom head semi hollow rivets be used in plastic without cracking the boss?

A: Yes – that is one of the main advantages of the mushroom head. The wide, low dome distributes the setting force over a larger area than a round head. For plastic, we recommend a barrel length exactly 1.0–1.5mm longer than the material thickness. Also use a press (not a hammer) to apply steady force. For the folding chair case, the hinge was metal, but we have used mushroom head rivets in ABS and polycarbonate with good results. Send us your plastic sample, and we will test.

Q3: Your standard mushroom head has a large edge radius. Is that necessary?

A: Yes. The radius is not cosmetic – it prevents the head from cutting into soft materials. A sharp edge under the head would act like a knife when the material flexes. Our mushroom head has a continuous 0.3–0.5mm radius from the shank to the outer edge. This eliminates stress risers. For the caster, that radius prevented the bracket from cracking around the rivet hole. For the chair, it kept the fabric from fraying. If you need a sharper edge (e.g., for decorative reasons), we can modify the tooling, but we will warn you about the trade‑off.

How Did The Customers We Cooperated Say ?

Confirm the Fit on Your Actual Assembly

Every material behaves differently. Rather than guessing, we suggest a simple test. Tell us your shank diameter, barrel length, and material. We will produce a small batch and ship it to you. Set them into your actual component. Measure the clinch. Check the head profile. Only then decide on production.

Contact Nuote Metals – send your drawing or just the specs.