Drawing
Selection table
One row per thread size, with its own link (/parts/nutplates/ms21055/#MS21055-04). The part number shown is the dry film lubricated, plain-hole form; the letters below change finish and holes, not size.
| Part no. | Thread | A max | C | J | H max | Ø K | Ø P max | V max | Axial, lbf min | lb / 100 |
|---|---|---|---|---|---|---|---|---|---|---|
| MS21055L04 | 4-40 | .637 | .344 | .486 | .143 | .098 | .166 | .047 | 750 | .20 |
| MS21055L06 | 6-32 | .637 | .344 | .486 | .171 | .098 | .206 | .047 | 1,130 | .25 |
| MS21055L08 | 8-32 | .637 | .344 | .486 | .250 | .098 | .248 | .047 | 1,720 | .28 |
| MS21055L3 | 10-32 | .653 | .344 | .486 | .250 | .098 | .274 | .047 | 2,460 | .29 |
| MS21055L4 | 1/4-28 | .852 | .500 | .707 | .281 | .098 | .344 | .055 | 4,580 | .58 |
| MS21055L5 | 5/16-24 | .914 | .500 | .707 | .328 | .130 | .417 | .065 | 7,390 | .85 |
Inches. From Table I of MS21055 Rev. G (1 Feb 1994). 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 |
|---|---|
| MS21055-08 | Plain rivet holes, no dry film lubricant |
| MS21055L08 | Dry film lubricant (L) |
| MS21055-08K | Countersunk or dimpled rivet holes (K) |
| MS21055L08K | Both |
K (countersunk or dimpled rivet holes) is listed for dash 04, 06, 08, 3, 4, 5. Without lubricant the L becomes a dash.
What it is for
All-metal fixed self-locking corner nutplate; rivet holes at 90° for installation in corners and at flange intersections. Steel, 125 ksi, 450 °F. Rated to 450 °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
- MS21055 Rev. G, 1 Feb 1994 — Nutplate, Self-Locking, Corner, Low Height — 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.