Industry News

Blind rivet selection guide: open-end, closed-end and structural rivets

2026-09-02

Compiled by JIALI Industrial (164.hk) — a Hong Kong fastener supplier specialising in screws, bolts, nuts and selection know-how.

Blind rivet types and characteristics

Blind rivets allow single-side installation without access to the back of the workpiece, making them ideal for sheet-metal enclosures, ventilation ducts and vehicle body assembly. Open-end rivets (DIN 7337) are the simplest and most cost-effective, suited for general-strength joints. Closed-end rivets seal the mandrel head inside the body, offering better water and dust resistance for sealed applications. Structural rivets (mono-lock, multi-lock) form a larger blind-side bulb after setting, delivering higher tensile and shear strength for demanding joints or soft substrates. The difference between the three types comes down to what happens on the blind side and to the mandrel. In an open-end rivet, the mandrel head pulls into the body, expands the tail and then snaps at a pre-weakened point; the tail remains open, so a path exists through the rivet for water and vapour. In a closed-end rivet, the body is made as a cup so that the mandrel head is retained inside and the set rivet is sealed at the tail; this costs slightly more but removes the leak path and also prevents the broken mandrel from falling into the assembly, which matters where loose metal inside a duct or an enclosure would be unacceptable. A structural rivet uses a different mechanism again: the mandrel may be retained rather than broken off, or the body may be designed to form a wide, folded bulb that spreads the load over a larger area of the sheet, and the result is markedly higher shear and tensile values plus far better resistance to vibration. Where a joint is structural, such as a bracket carrying a load rather than merely holding a panel in place, the choice is between a structural rivet and a threaded fastener, and a standard open-end rivet is not a substitute for either. There is also a further class used in thin or soft substrates: a large-flange or wide-head rivet spreads the clamping load and prevents the head pulling through soft material, and a peel-type or multi-grip rivet compensates for variations in total thickness, which is useful where sheet tolerances accumulate.

Material pairings and selection tips

Common material combinations include aluminium body with steel mandrel, aluminium body with stainless mandrel, all-stainless, and copper body with steel mandrel. Aluminium with steel offers the best value for indoor sheet metal; aluminium with stainless improves corrosion resistance for outdoor or humid environments; all-stainless provides maximum corrosion resistance for coastal and chemical applications. Match the rivet diameter to total grip thickness — typically rivet length equals total grip plus about 1.5 times rivet diameter, with a hole 0.1-0.2 mm larger than the shank. Set out as a comparison table by application. Indoor enclosures, cabinets and ductwork, dry environment, light load — aluminium body with steel mandrel, open-end; the cheapest option and adequate where no moisture is present. Outdoor or humid service, moderate load — aluminium body with stainless mandrel, which keeps the low weight and cost of an aluminium body while removing the steel mandrel as a corrosion site; closed-end where water ingress matters. Coastal, marine or chemical plant, any load, and any application where the failed mandrel must not be left inside — all-stainless, closed-end or structural; the material cost is higher but the joint lasts without maintenance. Vehicle body and chassis work, vibration and structural load — structural rivet, which forms a large blind bulb and resists vibration far better than an open-end rivet; where the joint must also be weathertight, a sealed structural variant. Soft or thin substrates such as aluminium sheet under about 1 mm or composite panels — large-flange head or a peel-type rivet designed to spread load and accommodate thickness variation, taking care not to over-compress and dimple the panel. Two points govern most field problems. First, the hole diameter must match the rivet shank within a narrow band: too small and the rivet will not enter without deforming the sheet, too large and the rivet cannot fill the hole, so the joint is loose from the start and the mandrel may not break correctly. Second, grip range matters more than nominal length. A rivet whose grip range does not cover the actual total thickness either fails to clamp or cannot be set at all, and on a joint with several layers the total thickness should be measured rather than calculated from nominal sheet gauges.

Installation tips and common problems

Use a matching rivet tool (pneumatic or manual); after setting, the mandrel should break cleanly and the blind side should form a uniform bulb. Common issues include the mandrel not breaking (insufficient tool stroke or a rivet too long for the grip), the blind side not bulging (hole too large or grip too thin), and looseness (hole tolerance exceeded or rivet undersized). For volume use, run a trial set and pull-test to GB/T 3098.19 before full production. A worked example shows how much these details matter. A fabricator building aluminium duct access panels in 1.2 mm sheet originally used aluminium open-end rivets with a grip range that only just covered the joint thickness. Because the sheet gauge varied slightly between coils, some joints fell outside the grip range, the mandrel failed to break on a proportion of them, and a few panels came loose in service. Switching to a peel-type rivet with a wider grip range and a larger flange head removed the problem entirely, at a higher unit cost offset by the elimination of rework. The same discipline applies to the setting tool. A pneumatic tool must be set for the correct stroke and the correct nosepiece for the rivet diameter; using a worn nosepiece or the wrong size lets the rivet pull off-centre, which produces a tilted set and an asymmetrical bulb. On site, a manual tool is adequate for a few hundred rivets but should not be used for production quantities, because operator fatigue leads to incomplete sets that pass a visual check and fail later under load. Where the application is structural or safety-related, the acceptance test is a pull or shear test on sample joints made with the same tool, the same operator and the same rivet batch as production; a test on a bench-prepared sample by a trained technician does not represent what happens on the assembly line. Finally, consider the broken mandrels. In an open-end rivet the mandrel falls out on breakage, and in an enclosure that is a loose metal fragment with a corrosion potential of its own; in a food, electrical or electronics application, that alone can justify a closed-end rivet or a mandrel-retaining design.

Common pitfalls and acceptance points for blind rivets

Pitfall one is choosing rivets by diameter only. The grip range is the controlling dimension, and a rivet that fits the hole but not the total thickness will either fail to set or set without clamping. Pitfall two is matching a steel mandrel with an aluminium body on an outdoor job. The mandrel is a small steel component embedded in the joint and is the first place corrosion begins; where moisture is present, specify an aluminium or stainless mandrel as appropriate. Pitfall three is using open-end rivets where the joint must be weathertight or where a loose mandrel is unacceptable. A closed-end rivet costs marginally more and solves both problems. Pitfall four is assuming a blind rivet can carry a structural load. A standard open-end rivet is a fastening device for panels and enclosures, not a structural connection, and where the load path runs through the joint a structural rivet or a bolted connection is required. Pitfall five is mixing rivet batches or tool settings within a production run. Different batches can vary in body length and mandrel break load, and a joint that behaves in a pull test may not behave in production if the rivets come from two different lots. At acceptance, the practical checks are: measure the actual total thickness at the joint and confirm the rivet grip range covers it; verify the hole diameter against the rivet shank on a sample of holes drilled with the production tool; confirm the material combination is correct for the environment, checking particularly the mandrel material; confirm the rivet type is the specified one, since open-end, closed-end and structural rivets can look similar before installation; and for volume or load-bearing work, run pull tests to GB/T 3098.19 on samples from the production tool and operator, and record the results. During production, an inspector should check that the set head is fully formed, that the head is flush or seated as specified, and that no mandrel has been left protruding or dropped inside the assembly. Need blind rivet selection or samples? Contact JIALI Industrial (164.hk) with your grip thickness and application for fast matching.

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