coqui7
Aerospace
- Jun 12, 2014
- 1
- 0
- 0
CAN RIVET MS20470DD6-10 BE SUBSTITUTED BY MS20470DD6-10D?
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MS20470DD6-10 4
- Thread starter coqui7
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1
- #2
MAYBE
IT DEPENDS
IT WOULD BE EASIER TO EXPLAIN IF WE WEREN'T SHOUTING AT EACH OTHER.
The "D" at the end of the dash number indicates that the rivet has been anodized, rather than treated per MIL-C-5541-1a.
That might render its surfaces electrically insulated. Perhaps that would be a moot point after driving the rivets.
What is being fastened with the rivets in question?
You can actually get these???
STF
IT DEPENDS
IT WOULD BE EASIER TO EXPLAIN IF WE WEREN'T SHOUTING AT EACH OTHER.
The "D" at the end of the dash number indicates that the rivet has been anodized, rather than treated per MIL-C-5541-1a.
That might render its surfaces electrically insulated. Perhaps that would be a moot point after driving the rivets.
What is being fastened with the rivets in question?
You can actually get these???
STF
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1
- #3
NO.
MS20470DD rivets are 2024-T4.
Per NASM20470 there are ONLY (3) finish codes permitted for "DD" material code rivets: A, D or N which are all anodic coatings.
By definition, DD rivets are too "hard" to be driven in the "as received temper" [most likely crack when bucked]: they must be bucked in the solution heat treated/quenched ["W" or Ice-box] temper, which is a temporarily dead-soft temper that spontaneously ages to -T4 [again] after bucking..
The ONLY corrosion protective coating systems coating systems that will survive solution heat-treatment/quenching are anodic coatings [A, D, N]. The "no finish code" P/N You have indicated implies chromate conversion coating [CCC], that will NOT survive heat treatment [oxidize-off]... and WOULD NEVER be applied to any DD rivet by any reputable manufacturer.
CAUTION, the next high strength aluminum rivet is the "D" [2017-T4] material code rivet. This rivet can be bucked in the "as received [-T4]" temper up-to ~3/16 with some effort and skill. However to ease installation forces/effort [all diameters], D rivets can be bucked "more easily" in the solution heat treated/quenched ["W" or Ice-box] temper. Problem: almost any finish
MS20470DD rivets are 2024-T4.
Per NASM20470 there are ONLY (3) finish codes permitted for "DD" material code rivets: A, D or N which are all anodic coatings.
By definition, DD rivets are too "hard" to be driven in the "as received temper" [most likely crack when bucked]: they must be bucked in the solution heat treated/quenched ["W" or Ice-box] temper, which is a temporarily dead-soft temper that spontaneously ages to -T4 [again] after bucking..
The ONLY corrosion protective coating systems coating systems that will survive solution heat-treatment/quenching are anodic coatings [A, D, N]. The "no finish code" P/N You have indicated implies chromate conversion coating [CCC], that will NOT survive heat treatment [oxidize-off]... and WOULD NEVER be applied to any DD rivet by any reputable manufacturer.
CAUTION, the next high strength aluminum rivet is the "D" [2017-T4] material code rivet. This rivet can be bucked in the "as received [-T4]" temper up-to ~3/16 with some effort and skill. However to ease installation forces/effort [all diameters], D rivets can be bucked "more easily" in the solution heat treated/quenched ["W" or Ice-box] temper. Problem: almost any finish
Code:
can be applied to "D" rivets, IE: chromate conversion coating or anodic coatings. IF rivets are driven in the "as received" condition [temper], then they will have an intact corrosion protective coating, regardless of type [CCC or anodic]. However, IF they are to be driven in the "W" [as-quenched] temper the ONLY acceptable coatings are anodic [same reason as for the "DD" stated above].
NOTE. The installation differences explained above, force the "D" material code rivets to have dual NAS523 rivet codes, IE: (1) for installation in the "as received" temper [optional anodize or CCC finish]; and (1) for installation in the "ice-box" ["W"] temper [described above, mandatory anodize finish].
Regards, Wil Taylor
Trust - But Verify!
We believe to be true what we prefer to be true.
For those who believe, no proof is required; for those who cannot believe, no proof is possible.
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1
- #4
As an old sheet metal guy who has driven many DD style rivets most installations manuals call for dipping the DD rivet in sealant like 8802-B2 or epoxy primer paint before driving. After the rivets are heat treated and forzen the dia will change a little and most DD are tapped in the hole with a snug fit, the sealant or primer seals them. After two or three hits from a rivet gun the rivet material expands to fill the hole and work hardens very quickly. It takes experienced mechanics to install DD rivets, because timing is everthing from the ice box to proper installation. If a DD has to be re-shot the shop head will crack in most cases this is why it has to be install right the first few hits of the rivet gun and this comes with lots of experience. Installing DD rivets has no room for error.
I would encourage engineers to go down to the shop floor and inspect a few DD rivets after installation to see the end product. You may find the larger the DD rivet dia the shorter the mechanic will cut them so they drive eaiser. This can have bad effects later if the shophead is not the proper dia.
I would encourage engineers to go down to the shop floor and inspect a few DD rivets after installation to see the end product. You may find the larger the DD rivet dia the shorter the mechanic will cut them so they drive eaiser. This can have bad effects later if the shophead is not the proper dia.
there is a substitute for DD rivets available from Bombardier ... DN rivets (which are highly controlled AD rivets) have the strength of DD with none of the heat treat and ice box issues.
another day in paradise, or is paradise one day closer ?
another day in paradise, or is paradise one day closer ?
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1
- #6
coqui7
STACHE: good point.
Warm driven rivets [A, AD, D, E] usually can be "re-hit" one time after the initial driving operation to adjust ['fix'] minor bucking discrepancies. However 'icebox' [SHT/quenched/frozen] rivets cannot be 're-hit' due to the severe cold working they undergo that deforms/hardens them VERY FAST.
CAUTION.
'Wet-sealant installation' of solid rivets is [NOW] generally discouraged by USAF and MOST OEMs. USAF recommends "wet-epoxy-primer" installation where enhanced corrosion resistance is required; whereas OEMs use little/no primer and may install special rivets [precision/tighter and/or special coatings] in high corrosion areas to speed-along production-assy.
Reason: sealant must be squeezed-out from under the heads and along the shank BEFORE bucking to prevent 'hydraulic-lock' action of the thick sealant from interfering with the mechanical settling/swelling of the rivet for a high mechanical tight fit. This usually requires the head of the rivet to be held tightly in-place for a few seconds before actual bucking begins [etc]. Also, sealant [which was intended to improve sealing and exclude moisture or pressure/fluid [fuel, etc] leakage] really gums-up everything it touches [what a mess]; and a tight rivet install [W/WO epoxy primer] tends to be a remarkably leak-proof joint.
SOMETIMES, the higher strength MS20470E [7050] can replace DD's... with engineering approval. These rivets require special riveting techniques/training and may NOT have same fatigue enhancement due to these issues if driven "improperly". However, driven properly these rivets work just fine [devil is in the details].
Regards, Wil Taylor
Trust Me! I'm an engineer!
Trust - But Verify!
We believe to be true what we prefer to be true.
For those who believe, no proof is required; for those who cannot believe, no proof is possible.
Unfortunately, in science what You 'believe' is irrelevant – "Orion"
STACHE: good point.
Warm driven rivets [A, AD, D, E] usually can be "re-hit" one time after the initial driving operation to adjust ['fix'] minor bucking discrepancies. However 'icebox' [SHT/quenched/frozen] rivets cannot be 're-hit' due to the severe cold working they undergo that deforms/hardens them VERY FAST.
CAUTION.
'Wet-sealant installation' of solid rivets is [NOW] generally discouraged by USAF and MOST OEMs. USAF recommends "wet-epoxy-primer" installation where enhanced corrosion resistance is required; whereas OEMs use little/no primer and may install special rivets [precision/tighter and/or special coatings] in high corrosion areas to speed-along production-assy.
Reason: sealant must be squeezed-out from under the heads and along the shank BEFORE bucking to prevent 'hydraulic-lock' action of the thick sealant from interfering with the mechanical settling/swelling of the rivet for a high mechanical tight fit. This usually requires the head of the rivet to be held tightly in-place for a few seconds before actual bucking begins [etc]. Also, sealant [which was intended to improve sealing and exclude moisture or pressure/fluid [fuel, etc] leakage] really gums-up everything it touches [what a mess]; and a tight rivet install [W/WO epoxy primer] tends to be a remarkably leak-proof joint.
SOMETIMES, the higher strength MS20470E [7050] can replace DD's... with engineering approval. These rivets require special riveting techniques/training and may NOT have same fatigue enhancement due to these issues if driven "improperly". However, driven properly these rivets work just fine [devil is in the details].
Regards, Wil Taylor
Trust Me! I'm an engineer!
Trust - But Verify!
We believe to be true what we prefer to be true.
For those who believe, no proof is required; for those who cannot believe, no proof is possible.
Unfortunately, in science what You 'believe' is irrelevant – "Orion"
402doctor (Aerospace)
While this may be true, aircraft mechanics are restricted to what is written in the SRM for a particular aircraft. Therefore it is sometimes more expedient to use the prescribed repair method, than wait around for an engineering approval, on a different method.
B.E.
You are judged not by what you know, but by what you can do.
While this may be true, aircraft mechanics are restricted to what is written in the SRM for a particular aircraft. Therefore it is sometimes more expedient to use the prescribed repair method, than wait around for an engineering approval, on a different method.
B.E.
You are judged not by what you know, but by what you can do.
rb... intriguing...
Any idea as what the 'DN' code equates to [RE: alloy/temper]?
Regards, Wil Taylor
Trust Me! I'm an engineer!
Trust - But Verify!
We believe to be true what we prefer to be true.
For those who believe, no proof is required; for those who cannot believe, no proof is possible.
Unfortunately, in science what You 'believe' is irrelevant û "Orion"
Any idea as what the 'DN' code equates to [RE: alloy/temper]?
Regards, Wil Taylor
Trust Me! I'm an engineer!
Trust - But Verify!
We believe to be true what we prefer to be true.
For those who believe, no proof is required; for those who cannot believe, no proof is possible.
Unfortunately, in science what You 'believe' is irrelevant û "Orion"
Hmmmm...
Per MMPDS-08
Alloy-temper//Driven FSu
AD [2117-T4]//30-KSI
D [2017-T4]//38-KSI
DD [2024-T4]//41-KSI
I simply don't see how an AD [alloy] could be altered to meet D or DD [alloy] strength
I wonder if DN is actually a highly controled D [2017-T4] that drives more like an AD [2117-T4]
DNs may also be another/similar alloy/temper [2xxx-Tx]
NOTE.
I have 'loosely' allowed D rivets as substitutes for DD rivets for years... presuming most applications require a 1/32-OS of the hole during repair-replacement. However ADs can only be substituted for Ds or DDs under strict authority of stress engineers... and ONLY when holes must be oversized for repair purposes... and when the added ductility of the AD is needed for larger diameters or when installed in NACA countersinks or when installed by the NACA method; and D or DD rivets simply aren't available.
Regards, Wil Taylor
Trust Me! I'm an engineer!
Trust - But Verify!
We believe to be true what we prefer to be true.
For those who believe, no proof is required; for those who cannot believe, no proof is possible.
Unfortunately, in science what You 'believe' is irrelevant û "Orion"
Per MMPDS-08
Alloy-temper//Driven FSu
AD [2117-T4]//30-KSI
D [2017-T4]//38-KSI
DD [2024-T4]//41-KSI
I simply don't see how an AD [alloy] could be altered to meet D or DD [alloy] strength
I wonder if DN is actually a highly controled D [2017-T4] that drives more like an AD [2117-T4]
DNs may also be another/similar alloy/temper [2xxx-Tx]
NOTE.
I have 'loosely' allowed D rivets as substitutes for DD rivets for years... presuming most applications require a 1/32-OS of the hole during repair-replacement. However ADs can only be substituted for Ds or DDs under strict authority of stress engineers... and ONLY when holes must be oversized for repair purposes... and when the added ductility of the AD is needed for larger diameters or when installed in NACA countersinks or when installed by the NACA method; and D or DD rivets simply aren't available.
Regards, Wil Taylor
Trust Me! I'm an engineer!
Trust - But Verify!
We believe to be true what we prefer to be true.
For those who believe, no proof is required; for those who cannot believe, no proof is possible.
Unfortunately, in science what You 'believe' is irrelevant û "Orion"
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