Does a MS20426DD rivet can be replaced by a MS20426AD rivet
Does a MS20426DD rivet can be replaced by a MS20426AD rivet
(OP)
Can someone please help me on this, can a MS20426DD rivet can be substituted by a MS20426AD rivet, I search on the National Aerospace Standards and it tells me that the DD or D rivets are inactive for new design, does anyboy know what would be a good substitute?.
Thanks for your time.
Regards!
Thanks for your time.
Regards!





RE: Does a MS20426DD rivet can be replaced by a MS20426AD rivet
check chapter 8 in Mil-Hdbk 5 (or AR-MMPDS-01)
DD can be substituted by E or ND
RE: Does a MS20426DD rivet can be replaced by a MS20426AD rivet
"AD" [2117-T4] "D" [2017-T4] and "DD" [2024-T4] are definitely not the same.
D and DD rivets have a version [anodized finish ONLY] that can be heat treated and quenched... then be driven [shot] in the "W" temper. Freezing these rivets immediately after quenching will preserve the W temper for a short while, allowing them to be driven at a later date. but BE CAREFUL... they are time-out-of quench sensitive. When they age harden in-place they assume the -T42 temper.
D rivets can be driven "hard" [in the -T3 temper] without cracking... but they are very tough to drive much larger than 3/16-Dia [a good reason for shooting larger rivets in the "W" temper]. Larger D rivets can be mechanically squeezed with care. NOTE: D rivets can have a chemical conversion coating [CCC] or anodized finish: DO NOT HEAT TREAT the CCC rivets: You will destroy the CCC finish [anodize finish will survive HT just fine]!!!
The "E" [7050-T73] rivet is not easy to drive "hard" [as heat treated]... but will match/exceed the strength of the D and DD rivets driven "ice-box".
Note: the D and DD rivets may be labeled "inactive for new design"... but that doesn't mean they are unavailable! CHECK!!!! Lots of older acft use these rivets!
Note: in-a pinch, I have substituted one larger diameter AD [typically 1/32] rivet for a D or DD rivet [SMALLER DIAS ONLY]. In this case they have roughly the same installed strength
CAUTION: check the static shear ultimate numbers first in MMPDS or a corporate design manual FIRST. For odd-oversize driven rivets [Example: NAS1241, NAS1242] You may have to estimate drilled hole size and then do P/A calculations to compare shear strength. P = driven shear strength [KSI] for the alloy. A = area of the rivet hole.
Regards, Wil Taylor
RE: Does a MS20426DD rivet can be replaced by a MS20426AD rivet
RE: Does a MS20426DD rivet can be replaced by a MS20426AD rivet
i'm surprised you're using a DD to fill a hole. i'd be an AD (as i think they have better hole filling and less processing restrictions).
just my 2c
RE: Does a MS20426DD rivet can be replaced by a MS20426AD rivet
A DD in the AQ condition ( before the time limits expire) is softer than an AD rivet.
B.E.
RE: Does a MS20426DD rivet can be replaced by a MS20426AD rivet
Up-to-about 3/16" or 7/32" Dia, most good mechanics can hand-drive "hard rivets". Squeeze equipment can drive larger "hard rivets" up-to about ~3/8" Dia no-sweat.
Rivets larger than these Dias should be driven in the "soft" W temper. I have heard mechanics describe installing these "soft" rivets like driving butter. "W" temper rivets up-to 3/8" Dia are generally easy to shoot by hand... and experienced mechanics can hand-shoot slightly larger sizes.
CAUTION.
I have heard mechanics say they are shooting "annealed" rivets which is entirely incorrect... the annealed temper [solution heat treated and air cooled] will not significantly harden after shooting [minor strain hardening only] and will have disastrous structural consequences.
2xxx alloy rivets properly solution heat treated and water-quenched "by the book"... and shot while in the [soft] "W" [post quench unstable] temper... will spontaneously age harden [in-place] to the -T42 temper and be very strong [MMPDS values]. Note: freezing after the quench [0F down to -40F] will grossly delay [or stop] the spontaneous age-hardening process and allow mechanics "working" time.
Regards, Wil Taylor