MS20426 — Solid Countersunk Rivet, 100° Precision Head
MS20426 covers solid rivets with a 100° countersunk precision head, produced in aluminum alloy and titanium-columbium alloy. Revision L (14 September 1993) superseded the earlier AN426 designation and has itself since been folded into NASM20426, though MS20426 part numbers remain the industry-standard callout in aircraft sheet metal work.
At a Glance
Overview
MS20426 covers solid rivets with a 100° countersunk "precision" head, manufactured from aluminum alloy or titanium-columbium alloy, and produced under the procurement specification MIL-R-5674. The countersunk head allows the rivet to sit flush with the surface once installed, making it the standard choice for aerodynamically smooth aircraft skin panels and structural lap joints.
The most common variant is the "AD" material code, made from 2117 aluminum alloy heat treated to the T4 condition, giving a shear strength around 26,000 PSI and a tensile strength around 38,000 PSI. A softer "A" material code (1100 pure aluminum) is also available for applications needing a more ductile rivet. Finish is typically chemical film per MIL-C-5541 or anodize per MIL-A-8625.
Installed correctly, a MS20426 rivet fills the drilled hole and forms a shop head on the blind side that clamps the two sheets together in shear — unlike a bolted joint, the fastener itself carries load almost entirely in shear rather than tension, which is why hole preparation, edge distance, and rivet-to-hole clearance are tightly controlled on aircraft structural drawings. Correct dimpling or countersinking of the top sheet is equally critical so the 100° head seats flush without proud material or a step.
- Installation requires access to both sides of the joint along with a rivet gun/hammer and a bucking bar.
- Revision L (1993) superseded the older AN426 designation used before the AN-to-MS hardware consolidation.
- MS20426 has since been folded into the AIA/NAS-maintained NASM20426 document, though the "MS20426" part number prefix remains in universal industry use.
Part Number Reference
MS20426 part numbers combine a material code, diameter dash, and length dash.
MS20426 / AN426 / NASM20426 Lineage
| Designation | Status |
|---|---|
| AN426 | Original Army-Navy designation — superseded |
| MS20426 (Rev. L) | Superseded AN426; industry-standard part number still in universal use |
| NASM20426 | Current AIA/NAS-maintained governing document |
Compliance & Sourcing References
Verify the current governing document and procurement history through official government and industry sources.
The current NASM20426 governing document, along with historical MS20426 revisions, can be verified through the Defense Logistics Agency's ASSIST QuickSearch portal. NSN cross-references and procurement history for MS20426 rivet hardware can be checked via DLA DIBBS. Ananka Fasteners manufactures MS20426 rivets to the current active revision and supplies full Mill Test Certification with every shipment.
MS20426 is closely related to MS20427 (the same 100° countersunk head style in carbon steel, CRES, Monel, and copper) and MS20470 (universal/dome-head rivets in aluminum and titanium-columbium alloy). All three families are now maintained under their respective NASM-prefixed successor documents.
MS20426 — Frequently Asked Questions
What does the "AD" in MS20426AD3-3 mean?
"AD" is the material code for 2117-T4 aluminum alloy — the most common MS20426 rivet material, offering a good balance of strength and workability for aircraft sheet metal.
Is MS20426 still the correct document to reference?
MS20426 has been superseded by NASM20426 at the governing-document level, but the "MS20426" part number prefix remains the universal industry callout for this rivet family and is still what most drawings and catalogs use.
What's the difference between MS20426 and MS20427?
Both use the same 100° countersunk precision head geometry, but MS20426 covers aluminum and titanium-columbium alloy rivets, while MS20427 covers the same head style in carbon steel, corrosion resistant steel, Monel, and copper.
Why is the 100° countersunk head used instead of a protruding head?
The 100° countersunk head seats flush with the surrounding skin, which keeps aerodynamic drag down and avoids a protruding profile — the standard choice anywhere the rivet sits on an exterior aircraft surface.
Does Ananka Fasteners supply Mill Test Certification with MS20426 rivets?
Yes, every shipment includes full Mill Test Certification and material traceability documentation covering chemistry, mechanical properties, and finish.
Need MS20426 Rivets?
Ananka Fasteners supplies MS20426 solid countersunk rivets with full material traceability and Mill Test Certification.
Prefer email? sales@anankafasteners.com
