Pop Rivet: Clamping Metal From One Side With a Mandrel That Snaps

Anatomy of a Break-Mandrel Blind Rivet

A pop rivet is a break-mandrel blind rivet, sold as two parts already assembled. The body is a hollow tube of 5056 aluminium (an aluminium–magnesium alloy with 4.5–5.6% Mg; 5154 is also used) with a flange head on one end. Threaded through it is the mandrel, a stem of low-carbon steel, typically 1006. The mandrel's head sits beyond the tail of the body and is wider than the body's bore, and a notched break-neck is formed in the stem just behind that head. The side you work from is the access side; the far side, which you may never see, is the blind side.

Inch sizes use a compact code. AD42 reads: A for aluminium body, D for dome head, 4 for a 4/32 in (1/8 in) diameter and 2 for a 2/16 in (1/8 in) maximum grip. Grip is the total thickness being joined, not the rivet length: an AD42 covers 0.063–0.125 in from a body 0.275 in long. The metric counterpart, ISO 15977, gives a 3.2 mm rivet a body 3.05–3.28 mm in diameter, a head 5.8–6.7 mm across, a mandrel no thicker than 2.0 mm and at least 25 mm of stem protruding from the head; a 3.2 × 8 mm rivet grips 3–5 mm of material.

Step by Step: From Drilled Hole to Snap

• Drill. A 1/8 in (3.2 mm) rivet needs a #30 drill, which gives a 0.129–0.133 in hole; ISO 15977 specifies 3.3–3.4 mm. Burrs are removed and the sheets held tightly together.
• Insert. The rivet goes in mandrel head first until the flange sits on the near sheet, leaving the tail and mandrel head poking out on the blind side.
• Engage. The riveter's nosepiece slides over the stem until it bears on the flange, with the tool square to the surface.
• Pull. On each squeeze, tapered jaws bite the stem and draw it back while the nosepiece pushes on the rivet head. The pull and the push are equal and opposite forces in one closed force loop: jaws, stem, mandrel head, rivet body, flange, nosepiece and tool frame. Nothing has to touch the hidden side. Between squeezes the jaws let go and take a fresh bite further along the stem.
• Form. The mandrel head, wider than the bore, is driven into the tail and cold-flows the aluminium. Squeezed between the mandrel head and the nosepiece, the tail barrels outward into a bulb larger than the hole, while the shank swells to fill the hole's clearance. As the bulb grows it draws the sheets together.
• Seat. Once the bulb bears on the back sheet, the sheet stack joins the force loop in compression. Little is left to deform, so the force climbs steeply over a tiny extra stroke.
• Snap. The break-neck, the weakest link in the loop, fractures at 400–600 lbf (1.8–2.7 kN) for a 1/8 in aluminium/steel rivet (SAE J1200). The mandrel head stays wedged in the bulb; the rest of the stem recoils into the tool and is ejected as scrap.

The Governing Relations: A Mechanical Fuse, Worked Through

The break-neck is a calibrated mechanical fuse, and the design depends on an ordering of loads. The force needed to form and seat the bulb must be lower than the mandrel break load, which must in turn be lower than the force that would drag the mandrel head through the body or pull the bulb through the hole. Set the break too low and the neck fails before the bulb seats, leaving a loose joint. Set it too high and the tool crushes thin sheet or pulls the bulb through soft material. So SAE J1200 set a window of 400–600 lbf (1.8–2.7 kN) for the 1/8 in aluminium/steel size, while ISO 15977 caps the 3.2 mm mandrel break load at 3,500 N as a ceiling rather than a target.

Worked example: the stem at the instant of the snap. Take a 1/8 in rivet with a ~1.93 mm (0.076 in) steel stem.

• Area: A = πd²/4 = π × (1.93 mm)² / 4 ≈ 2.93 mm².
• Stress: σ = F/A. At 1.8 kN, σ ≈ 1,800 N ÷ 2.93 mm² ≈ 615 MPa; at 2.7 kN, σ ≈ 920 MPa. The stem carries ~600–900 MPa just before the snap, and the notch concentrates stress further at the neck, which is why the neck fails first.
• Stored energy: with E ≈ 200 GPa, strain ε = σ/E ≈ 0.3–0.46%, so a 25 mm length of stem is stretched by ~0.08–0.12 mm and stores U = F²L/(2AE) ≈ 0.07–0.16 J.
• Release: fracture turns the neck into a free surface, and the stored stress unloads as an elastic wave running up the stem at c = √(E/ρ) = √(200 × 10⁹ Pa ÷ 7,850 kg/m³) ≈ 5,050 m/s, or ~5,100 m/s for E = 207 GPa. It crosses 25 mm in t = L/c ≈ 0.025 m ÷ 5,100 m/s ≈ 4.9 µs, about 5 µs.
• Recoil: behind the wave the steel moves at v = σ/(ρc) ≈ (600–900 MPa) ÷ (7,850 kg/m³ × 5,100 m/s) ≈ 15–23 m/s, back toward the jaws. That sudden jerk, reaching the tool within microseconds, is much of the pop you hear and feel in the handles.

A hand riveter's lever linkage multiplies a firm squeeze roughly tenfold or more to reach these loads.

Standards, Specifications and How Pop Rivets Are Tested

Break-mandrel blind rivets are specified in inch sizes by the Industrial Fasteners Institute's IFI-114, which superseded SAE J1200 when SAE cancelled it in 2017 (J1200's tables remain the widely quoted reference), and in metric by ISO 15977 (open end, aluminium body and steel mandrel, protruding head) and ISO 15973 (the sealed, closed-end version), using the test methods of ISO 14589. Beyond dimensions, hole sizes and grip ranges, they set four kinds of mechanical requirement:

• Shear: a rivet set through test plates is loaded across its shank until it fails. Published minimums for a 1/8 in 5056 aluminium/steel dome-head rivet such as the AD42 are ≥170 lbf (756 N). ISO 15977 splits the 3.2 mm size into class L (≥500 N) and class H (≥750 N).
• Tension: the set rivet is pulled along its axis until the head, body or bulb gives way: ≥220 lbf (979 N) for the 1/8 in rivet, and ≥700 N (class L) or ≥1,100 N (class H) under ISO 15977.
• Mandrel break load: the peak setting force, recorded while setting rivets in a test plate: 400–600 lbf (1.8–2.7 kN) under SAE J1200, and no more than 3,500 N under ISO 15977.
• Mandrel retention: in an unset rivet the mandrel must resist a push-out load above 10 N, and the retained head of a set 3.2 mm rivet must survive a 15 N ejection test, so spent heads do not rattle loose into equipment.

ISO 15977 also demands no cracks visible at 5× magnification after setting, and warns that holes outside 3.3–3.4 mm can reduce the rated loads. Automated production tools often record a force–stroke curve for every rivet and reject outliers.

History: Wylie, Tucker and the POP Brand

A solid rivet needs a hand on each side: one on the head and one bucking the tail. British engineer and Royal Navy reservist Hamilton Neil Wylie set out to remove the second hand. Wylie filed his blind-rivet patent in 1916, granted in 1917 as an improved means of closing tubular rivets. After joining the aircraft maker Armstrong Whitworth in the 1920s he filed his pull-through mandrel patent in 1927, in which a mandrel dragged through a tubular rivet expands it from one side. The timing mattered: as airframes moved from wood and fabric to all-metal construction, closed wing and fuselage sections left no room for a bucking bar.

Birmingham's George Tucker Eyelet Co., a maker of boot eyelets, built on Wylie's work from 1928; its early blind rivets reportedly needed the mandrel fitted by hand. Tucker's POP trade name stuck so firmly that "pop rivet" became the generic term. The later pre-assembled break-mandrel form made it cheap enough for appliances, vehicles and building products. Through a chain of owners, including the United Shoe Machinery Corporation, Emhart and Black & Decker, the POP brand now belongs to Stanley Engineered Fastening.

How Pop Rivets Fail or Get Misused

• Wrong grip. A rivet too long for the stack forms its bulb away from the back sheet or folds over, holding the sheets loosely. A rivet too short leaves too little tail to form a full bulb. Match the grip range to the measured thickness.
• Oversized or ragged holes. The shank can swell only so far. A hole drilled with a 9/64 in bit (0.141 in) instead of a #30, or a hole worn oval in soft material, loses strength and lets the bulb pull through. Thin or soft materials call for large-flange heads, backup washers or splitting "petal" rivets that spread the load.
• Gaps and burrs. If the sheets are not clamped, the body can swell into the gap between them instead of drawing them together.
• Galvanic corrosion. An aluminium body in stainless steel or copper, or a plain-steel mandrel stub exposed to rain, forms a galvanic cell; rust streaks from the mandrel are a classic sign. Outdoor and marine work uses all-aluminium, stainless or Monel rivets.
• Treating it as structural. A hollow, soft aluminium tube with modest clamp force handles fatigue and vibration poorly and can work loose. Certified aircraft primary structure uses solid rivets or locked-spindle structural blind rivets, not hardware-store pop rivets.
• Misconception: "it popped, so it is tight." The snap proves only that the neck reached its break load. A rivet set at an angle, in an oversized hole or with the wrong grip can still snap cleanly.

To remove one, drill off the head with the same #30 bit and tap out the shank; drilling oversize ruins the hole for the replacement.

Pop Rivet vs Solid Rivet, Rivnut and Structural Blind Rivets

• Solid rivets (MS20470). A solid aluminium shank set from both sides: a rivet gun hammers the head while a bucking bar upsets the tail into a flat shop head. It fills the hole completely, carries roughly twice the shear of a 1/8 in pop rivet and remains the default for aircraft skins, but it needs access to both sides.
• Rivnut (BF Goodrich, 1936). Created to attach rubber de-icing boots to wing leading edges, the rivet nut is a threaded tube. Its tool screws a threaded mandrel in, pulls to collapse a bulge on the blind side, then unscrews. Nothing snaps, and what is left is a nut that takes a bolt.
• Locked-spindle structural blind rivets. Carl Cherry applied in 1937 for the blind rivet patented in 1939; that line led to Cherrylock and CherryMAX rivets, in which a locking collar traps the stem inside the rivet and the stem fractures flush with the head. The retained steel fills the bore and carries load, which qualifies them for aircraft structure. A pop rivet's mandrel head is merely wedged in the tail.
• Pull-through mandrel rivets. Wylie's 1927 principle survives in Avdel's Chobert rivets: the mandrel passes right through the bore and is reused, leaving an open tube.

Pop rivet versus the fasteners it is mistaken for

Fastener	Access and setting	What stays in the joint	Typical use
Pop rivet (break-mandrel blind rivet, e.g. AD42)	One side; jaws pull the stem while the nosepiece pushes the flange; neck snaps at 400–600 lbf (1.8–2.7 kN) for 1/8 in	Hollow 5056 aluminium body with a bulb; the steel mandrel head wedged in the tail	Sheet metal, ducting, trailers, trim; ≥170 lbf (756 N) shear at 1/8 in
Solid rivet (MS20470)	Both sides; a rivet gun hammers the head while a bucking bar upsets the tail	Solid aluminium shank that fills the hole, with a flattened shop head	Aircraft skins and structure; roughly double the shear of a 1/8 in pop rivet
Rivet nut (Rivnut, BF Goodrich, 1936)	One side; a threaded mandrel is screwed in, pulled to collapse a bulge, then unscrewed	A threaded insert: nothing snaps	A removable bolted attachment in thin sheet
Locked-spindle structural blind rivet (Cherry lineage, e.g. CherryMAX)	One side; the stem is pulled, a locking collar traps it, and it fractures flush	Stem mechanically locked through the grip, filling the bore	Aircraft structure where no bucking bar can reach
Pull-through mandrel rivet (e.g. Avdel Chobert)	One side; the mandrel head is dragged all the way through the bore	An empty, expanded tube; the mandrel is reused	Light-duty, high-volume assembly