What it is and where it is used
Where to buyFAA-H-8083-31B (p. 4-55): the rivet nut was invented in 1936 by the Goodrich Rubber Company to attach a rubber wing de-icer to the leading edge; the original is the Rivnut made today by Bollhoff Rivnut Inc. Rivet nuts are used for fairings, trim and lightly loaded fittings that must be installed after an assembly is completed, often for parts that are removed frequently.
They come in two types, countersunk or flat head; the countersunk style is used where a flush fit is required. Rivet nuts of alloy steel are used when increased tensile and shear strength is required. The rivet nut size is selected according to the thickness of the parent material and the size of the screw; the part number identifies the type and the maximum grip length.
Reading the number
NAS1329A06-75: NAS1329 is the flat-head Rivnut; A is the unkeyed version (K at the end of the number marks keyed); 06 is the 6-32 thread; 75 is the end of the grip range, .075 in (grip .010 to .075 in). NAS1330A08-106 is the countersunk head, 8-32 thread, grip .065 to .106 in. MS27130 numbers are the same items, listed against the NAS numbers on the MS27130 data sheet (for example MS27130-A8 is the unkeyed flat head, 6-32 thread).
Threads on the NAS1329 sheet: 4-40, 6-32, 8-32, 10-32. On the NAS1330 sheet: 6-32, 8-32. Every grip row is on the NAS1329 and NAS1330 data sheets.
Hole by Rivnut size
| Rivnut size | Drill | Hole, in |
|---|---|---|
| No. 4 | 5/32 | .155–.157 |
| No. 6 | #12 | .189–.193 |
| No. 8 | #2 | .221–.226 |
FAA-H-8083-31B fig. 4-114, p. 4-56: Rivnut size, drill size and hole tolerance. The figure text lists the three columns in this order; read the rows across. Flat-head rivet nuts need only the proper hole; flush installation can be made in a countersunk or dimpled skin, and metal thinner than the rivet nut head needs a dimple. Correct installation requires good hole preparation, burrs removed and the sheets held in contact while heading (p. 4-56).
Questions people actually ask
Flat or countersunk?
Flat head where the head can stand proud; countersunk where the surface must be flush (FAA-H-8083-31B p. 4-55).
What does K mean at the end of the number?
The keyed version (the part number notes of the NAS1329 and NAS1330 sheets).
Can I use a Rivnut for a structural joint?
No: they are for lightly loaded fittings, fairings and trim.
Limits of this guide
What the sources support, and no further.
- Hole table: only the three sizes printed in the handbook figure; larger threads follow the maker's data.
- Material and finish codes are not stated in the data sheets used.
- No pull-out or torque-out values are given.
- Reference data, not approved data. The SRM, the drawing or the approved repair data governs over every figure here.
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Sources
- FAA-H-8083-31B, Aviation Maintenance Technician Handbook, Airframe, chapter 4 — P. 4-55 rivet nut; p. 4-56 fig. 4-114 recommended hole sizes.
- NAS1329, NAS1330 and MS27130 data sheets — Threads, grips, keyed and unkeyed numbers: the data sheets of this site.