The two heads, the marks and the standards
Where to buy
Is it Monel? What to look for
| Look at | What you see | Source |
|---|---|---|
| Head mark | Plain head, or two recessed dots (Monel nickel-copper alloy) | AC 43.13-1B Table 4-8 |
| Head mark, T.O. drawing | Two dots side by side | T.O. 1-1A-1 Table 5-2 |
| 100° head (MS20427) | No marking requirement for Monel or copper rivets | MS20427H note (b) |
| Part number | The letter M: MS20615-4M5, MS20427M4-5 | MS20427H; MS20615 listings |
| Plain heads that are not Monel | 1100 aluminium, copper and brass rivets are plain too | AC 43.13-1B Table 4-8 |
A plain head proves nothing by itself: read the part number on the bag or the drawing. MS20470 and MS20426 list no Monel letter, so a number such as MS20470M is not a part of those standards (MS20470H, MS20426L).
The standards that carry Monel
| Standard | Head | Materials in the standard | Status |
|---|---|---|---|
| MS20615 | Universal (protruding) | Brass, copper, nickel-copper alloy (title) | Rev. G, 1995; superseded by NASM20615 |
| MS20427 | 100° countersunk | Carbon steel, CRES, Monel (M), copper | Rev. H, 1994; superseded by NASM20427 |
| NAS1200 | 100° flush shear | Monel (data sheet title) | NAS standard: check the issue in force |
| AN435 (cancelled) | Round | Steel, Monel, copper | Replaced by MS20613 and MS20615 (AC 43.13-1B Table 4-8) |
| CherryMAX CR3522, CR3523 | 100° flush; universal (blind) | Monel sleeve; oversize CR3552, CR3553 | Cherry CA-1011; TM 1-1500-204-23-6 Table 2-11 |
Status as read on the standard or its public listing. The NASM issue in force governs and is not free to read. MS20427M and MS20615 are the same alloy with different heads, not equivalents of each other.
Reading the part number
Solid rivet numbers count the diameter in 1/32 in and the length in 1/16 in. Where the material letter sits depends on the standard.
MS20615-4M5: MS20615, diameter 4 (4/32 = 1/8 in), M for Monel, length 5 (5/16 in). MS20613F, the steel twin, uses the same order. Listings also show MS20615-4MP6 and half lengths such as MS20615-4M4.5; what the P and the .5 mean is not in a public text, so confirm the order with the supplier.
MS20427M4-5: Monel, 1/8 in diameter, 5/16 in long, 100° head. When cadmium plating is specified, a C replaces the dash: MS20427M4C5. An extra 1/32 in of length is -5 at the end: MS20427M3-3-5 is 3/32 in by 7/32 in (MS20427H).
The part number decoder reads solid rivet numbers segment by segment, and drill for a part number gives the drill from the number.
Drills, standard and oversize
| Rivet | Pilot | Final drill (in) | 1st oversize, 1/64 in | 2nd oversize: next size |
|---|---|---|---|---|
| 3/32 in (-3) | 3/32 (0.0938) | #40 (0.098) | No public part | 1/8 in: #30 (0.1285) |
| 1/8 in (-4) | 1/8 (0.125) | #30 (0.1285) | No public part | 5/32 in: #21 (0.159) |
| 5/32 in (-5) | 5/32 (0.1562) | #21 (0.159) | No public part | 3/16 in: #11 (0.191) |
| 3/16 in (-6) | 3/16 (0.1875) | #11 (0.191) | No public part | 7/32 in: #1 (0.228) |
| 7/32 in (-7) | None printed | #1 (0.228) | No public part | 1/4 in: F (0.257) |
| 1/4 in (-8) | 1/4 (0.25) | F (0.257) | No public part | 5/16 in (1/16 in step above 1/4 in); drill not in the public tables |
Pilot and final drill: FAA-H-8083-31B fig. 4-90; the final drills are confirmed in MIL-R-47196A Table I, which also lists #20 for 5/32 in and #10 for 3/16 in, and gives #1 for 7/32 in with no pilot. Both tables go by diameter, not by alloy. 2nd oversize: the next larger rivet, in steps of no more than 1/32 in up to 1/4 in and 1/16 in above (MIL-R-47196A 3.4.1, 3.4.2), with edge distance and spacing still at the minimums (AC 43.13-1B par. 4-57b). 1st oversize: the repair rivets NAS1241 and NAS1242 (shank 1/64 in over nominal in -4 and -5, 1/32 in over in -6 and -8; DLA FLIS) are 2117-T4 on their data sheets; no public 1/64 in Monel rivet was found. The SRM, the drawing or the approved repair data governs.
CherryMAX Monel: drill and hole
| Size | Nominal: drill (hole, in) | Oversize 1/64 in: drill (hole, in) |
|---|---|---|
| 1/8 in (-4) | #30 (0.129 to 0.132) | #27 (0.143 to 0.146) |
| 5/32 in (-5) | #20 (0.160 to 0.164) | #16 (0.176 to 0.180) |
| 3/16 in (-6) | #10 (0.192 to 0.196) | #5 (0.205 to 0.209) |
| 1/4 in (-8) | F (0.256 to 0.261) | I (0.271 to 0.275) |
Cherry CA-1011 Rev. A p. 16, drills and hole limits as Cherry prints them. Cherry makes nominal and 1/64 in oversize only, so there is no second oversize (p. 4). CR3522 (100° flush) and CR3523 (universal) are the nominal Monel rivets, CR3552 and CR3553 the oversize ones; TM 1-1500-204-23-6 Table 2-11 lists both as oversize. Whether every size is made in Monel is not checked here: confirm on the catalogue page. Grip: CherryMAX grip selector.
Shear strength
| Diameter | Single shear, driven, lb |
|---|---|
| 1/16 in | 183 |
| 3/32 in | 376 |
| 1/8 in | 674 |
| 5/32 in | 1,030 |
| 3/16 in | 1,490 |
| 1/4 in | 2,695 |
| 5/16 in | 4,260 |
| 3/8 in | 6,085 |
MIL-HDBK-5J Table 8.1.2(b): driven Monel, Fsu 52 ksi (undriven 49 to 59 ksi), B-basis, on the nominal hole of Table 8.1.2(a), with a shop head at least 1.5 times that hole (note e). AC 43.13-1B Table 4-8 gives 49,000 psi for both Monel columns; MS20427H asks 49,000 to 59,000 psi for M. The MIL-HDBK-5J joint tables use Fsu = 49 ksi for MS20427M (Tables 8.1.2.2(a), (b), (h)). The joint also depends on the sheet: rivet strength calculator and the SRM.
Where Monel rivets are used
AC 43.13-1B par. 7-2g: Monel rivets are for special cases, riveting high-nickel steel alloys and nickel alloys. They may be used interchangeably with stainless steel rivets because they drive more easily, but stainless steel rivets are preferred in stainless steel parts. T.O. 1-1A-1 par. 5.3.2.6 says the same: interchangeable with CRES rivets, with CRES recommended in CRES structures. See steel and CRES rivets.
FAA-H-8083-31B (p. 4-84) names Monel rivets, or standard close-tolerance steel fasteners, for installing titanium parts.
Which fastener goes against which metal is the SRM's call. In AC 43-4 Table 4-2, Monel is a nickel-base alloy and sits in Group IV with stainless steel and titanium; aluminium (Group II) and steel (Group III) are other groups, so each couple is dissimilar and needs the isolation the SRM calls for. The tables print no voltage for Monel, and this guide gives none.
Installing and checking
| Step | What to do | Source |
|---|---|---|
| Identify | Read the M in the part number; a plain head is not proof | AC 43.13-1B Table 4-8 |
| Heat treatment | None. Drive as received: no icebox | AC 43.13-1B Table 4-8 |
| Drill | Pilot, then the final drill of the diameter (table above) | FAA-H-8083-31B fig. 4-90 |
| Countersink | 100° for MS20427M and NAS1200 | MS20427H; NAS1200 title |
| Drive | Cold, to a full head free from cracks | MS20427H req. 4 |
| Shop head | At least 1.5 × the nominal hole for the strengths above | MIL-HDBK-5J Table 8.1.2(b) note e |
| Check | Shop head size, head seated, no cracks | Shop head calculator |
Questions people actually ask
How do I tell a Monel rivet from an aluminium one?
By the part number first. AC 43.13-1B Table 4-8 gives Monel a plain head or two recessed dots, but 1100 aluminium, copper and brass rivets also have plain heads, and MS20427H requires no mark on Monel 100° rivets. The letter M in an MS20615 or MS20427 number is the proof.
Does a Monel rivet need heat treatment or the icebox?
No. AC 43.13-1B Table 4-8 says no heat treatment for both Monel columns, and MS20427H calls for annealed Monel. Drive it as received.
Can I use a Monel rivet instead of a stainless steel one?
AC 43.13-1B par. 7-2g allows Monel and stainless steel rivets to be used interchangeably and prefers stainless steel rivets in stainless steel parts. The SRM or the drawing still decides for your repair.
Which drill for a 1/8 in Monel rivet?
#30 (0.1285 in) after a 1/8 in pilot (FAA-H-8083-31B fig. 4-90). The public drill tables go by diameter, not by alloy.
Limits of this guide
What the sources support, and no further.
- MS20615 dimensions. The MS20615G sheet was not read: the head values come from FLIS records of MS20615-4M and -6M5, which match the MS20613F table. No size table is printed here.
- The P of MS20615-4MP6 and the .5 half length appear in listings; their meaning is not in a public text.
- Drills by diameter. No public table gives drills by alloy for Monel; the drill is that of the diameter.
- No 1/64 in Monel repair rivet was found in the public data.
- 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 AC 43.13-1B CHG 1, Table 4-8 (pp. 4-17, 4-18) and par. 7-2g — Head marks, heat treatment and shear of Monel rivets; their use and interchange with stainless steel rivets.
- FAA-H-8083-31B, Aviation Maintenance Technician Handbook, Airframe, chapter 4 — Fig. 4-90 pilot and final drills; p. 4-84, fasteners for titanium parts.
- MIL-HDBK-5J (31 Jan 2003), Tables 8.1.2(a), 8.1.2(b), 8.1.2.2(a), (b), (h) — Nominal holes, driven shear of Monel rivets and the joint basis of MS20427M.
- MS20427 Rev. H (8 Feb 1994) — Materials, letters, head table, marking note (b), shear and driving requirements.
- MS20615 Rev. G (13 Feb 1995), public listing — Title and status; the sheet itself was not read.
- T.O. 1-1A-1 (NAVAIR 01-1A-1) — Par. 5.3.2.6, Monel and CRES rivets; Table 5-2, head marks.
- MIL-R-47196A(MI), 6 Sep 1977 — Table I drills; 3.4.1 and 3.4.2, the next larger rivet.
- Cherry Aerospace CA-1011 Rev. A (June 2012) — CherryMAX Monel part numbers, drills and hole limits (pp. 4, 8, 16).
- TM 1-1500-204-23-6, Table 2-11 — CherryMAX cross reference: oversize part numbers.
- US federal item records (DLA FLIS) — Head characteristics of MS20615-4M and -6M5.