Drawing
Selection table
One row per thread size, with its own link (/parts/nutplates/ms21081/#MS21081-04). The part number shown is the plain-hole form; the letters below change finish and holes, not size.
| Part no. | Thread | A max | B max | C | J | H max | Ø K | Ø P max | V max | Axial, lbf min | lb / 100 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| MS21081-04 | 4-40 | .650 | .344 | .344 | .486 | .218 | .098 | .166 | .075 | 750 | .75 |
| MS21081-06 | 6-32 | .703 | .406 | .344 | .486 | .234 | .098 | .177 | .075 | 1,130 | .85 |
| MS21081-08 | 8-32 | .703 | .406 | .344 | .486 | .297 | .098 | .230 | .075 | 1,720 | 1.00 |
| MS21081-3 | 10-32 | .703 | .406 | .344 | .486 | .312 | .098 | .230 | .075 | 2,460 | 1.00 |
| MS21081-4 | 1/4-28 | .906 | .514 | .500 | .707 | .375 | .098 | .293 | .075 | 4,580 | 1.60 |
| MS21081-5 | 5/16-24 | .937 | .582 | .500 | .707 | .375 | .130 | .354 | .075 | 7,390 | 1.90 |
| MS21081-6 | 3/8-24 | 1.008 | .718 | .500 | .707 | .453 | .130 | .418 | .075 | 11,450 | 2.50 |
Inches. From Table I of MS21081 Rev. D (20 Apr 1993). C ±.005, J ±.002, K +.005 −.000 as toleranced on the sheet. Ø P is the maximum barrel diameter. Weight is the standard's figure per 100 pieces. Rows shown are the sizes this sheet covers; the standard may list more.
How to read the part number
| Part no. | Meaning |
|---|---|
| MS21081-08 | Plain rivet holes |
| MS21081-08K | Countersunk or dimpled rivet holes (K) |
K (countersunk or dimpled rivet holes) is listed for dash 04, 06, 08, 3, 4, 5, 6. This standard's dash numbers carry no L form.
What it is for
Fixed corner self-locking nutplate with non-metallic (nylon) locking insert; rivet holes at 90°. Steel, 125 ksi, 250 °F maximum. Rated to 250 °F.
Rivet hole spacing J differs between nutplate types and sizes: check J before installing on an existing hole pattern.
Choose the size from the screw thread, then confirm J and C against the hole pattern and the edge distance of the flange it rivets to.
Limits — when NOT to use this
- Approved data governs. Use the nutplate and rivets the maintenance manual or IPC specifies.
- The MS sheet is a public-domain revision. These MS standards were later replaced by NASM equivalents. Check the current revision before buying to a drawing.
- Grip with nutplates. Where the proper bolt grip is not available, AC 43.13-1B par. 7-37 says to add shims under the plate, not washers.
- Rivets for the lugs, and their edge distance, come from the repair data, not from this sheet.
Sources
- MS21081 Rev. D, 20 Apr 1993 — Nutplate, Self-Locking, Corner, Nylon Insert — Table I, dash numbers and dimensions; notes and requirements. Public domain, distribution unlimited.
- FAA AC 43.13-1B, par. 7-37 — shims, not washers, under plate nuts.