aluminum rivets

[Victor Bravo]

Many of you guys obviously know the chemistry and materials cross-referencing far better than I do... my first question is would there be some chemical or galvanic conflict between a standard AD airplane rivet and the 5052 material being riveted?

Second question is if the softer 1100 "nearly pure" aluminum rivets were used for this, could you simply reduce the rivet spacing or increase the rivet diameter to achieve the same level of tear-out, or shear, or tensile strength as you would have gotten if you had found 5052 rivets?

Yes of course I understand these suggestions are "making an end-run" around what would have obviously been the right way to do it, but if you are having this kind of trouble finding the correct rivets, even through Hanson and other large suppliers, then you may have to consider an end run.

 

[Richard Roller]

"B" rivets, 5056, are commonly used with 5052 aluminum. They are both aluminum, magnesium alloys and work fine together. It's not that complicated. AD rivets will work also.

 

[David L. Downey]

Interesting, factories use salt bath. Heat treating at 940° needs accurate temperature control thermostats. Do they have that in kits? Or is it all self design?

just an aside here: when I worked at Cessna Business twins and jets/military in Wichita more than 35 years ago we did out onw heat treating with large salt baths. in spite of tremendous care, we had two events where water was accidentally introduced into the bath and the resulting explosion severely burned employees. Add to that what happens when you drop an ice cube into a deep fat fryer (looks just like a depth charge!) and consider the safety precautions needed if you are using this process at home.

 

[Richard Roller]

5052 aluminum and "B" rivets are both magnesium aluminum alloys. They are compatible corrosion wise and in strength. In a real world scenario "AD" rivets would work fine also, 5052 is very forgiving, especially in a "non-aviation" situation.

As far as "D" rivets in this case they most likely would cause some distortion due to the hardness of the rivet relative to the sheet material. When we had to use hard rivets in soft materials we would be required to put a steel washer under the the buck tail, opposite the head, to reduce deformation of the sheet.

An interesting note: Boeing allows certain sizes and orientation of cracks in the buck tails of rivets.

 

[BBerson]

Add to that what happens when you drop an ice cube into a deep fat fryer (looks just like a depth charge!) and consider the safety precautions needed if you are using this process at home.

Right. But it would only take a teaspoon of molten salt to heat treat 10 rivets for a homebuilder at a time.

 

[wktaylor]

Guuuuyyyys...

I want to caution everyone there are numerous misconceptions and miss-statements throughout this post. A few guys have made corrective statements... but not enough. And this starts with skittish’s presentation as to what rivets he was dealing with... ‘17-T4 really hard to drive’ with a raised dot.... which were probably purchased at a ‘bargain price’ surplus sale@... since they are rarely used anymore... except in antique/heavy jet [707, 727, DC-8, etc] structural repairs. @ on-a-dare, I will even bet that the label on the bag holding the rivets... if legible... indicates date of manufacture +25-years-ago.

In this case I would normally advise installing ‘B’ or ‘A’... or maybe ‘AD’... and NEVER mess with any heat treatment. OH by-the-way... I can’t figure-out WHAT finish was applied to the original rivets... and that has a large effect on this situation also.

Applying heat to these rivets for any purpose is a really bad idea... and in the long term You will not be happy with the results... even for the ‘non-aviation’ purposes described... “soften them so they can be installed ‘safely’ in 5052-O or –H32[?] aluminum sheet, tubes, etc.

Heat treating aluminum alloy rivets is as critical as heat treating aluminum parts: knowledge and hands-on training is essential.

1. First, let’s consider as-manufactured alloys solid rivets you are likely to use [specifications listed]

NASM20426 100-degree flush tension head [MS20426, was AN426]

NASM20470 protruding tension head [MS20426, was AN470]

NAS1097 100-degree flush shear [reduced-height] head

Alloy-code... head symbol... Alloy-temper... Finish

A... [none]... 1100-as forged.. CCC$

AD... depressed dot [dimple]... 2117-T4... CCC$ or Anodize#

B... raised cross [+]... 5056-H32... CCC$ or Anodize#

D... raised dot [tit/teat]... 2017-T4... CCC$ or Anodize#

DD... raised dash-dash [- -]... 2024-T4... Anodize# [only]

E... indented ring [o]... 7050-T73... CCC$ or Anodize#

KE... raised ring [o]... 7050-T73... CCC$ or Anodize#

3. How they are made.

High quality aluminum alloy wire per specification ASTM B318 [was] QQ-A-430] is fed into the cold heading machine coated with lubricant and are then forged/cut/rolled to a few standard shank lengths... 'shaped-blanks' of semi-finished size/length. These blanks have the rivet code symbol in the head... and may/may-not have the manufacturer's code-symbol [impressed, NOW or just before the finish is applied]

Formed ‘blank's are inspected’ for cracks, straightness, etc.

Heat treatable rivet alloys [AD, D, DD, K/KE] are heat treated to attain specified temper. Nondestructive testing and destructive testing validate the raw production lot.

The Blanks are then cut/trimmed to shank-length and other features added, as per purchase order.

Corrosion-protective finishes are applied, as required per purchase order... CCC$ or Anodize# ...

CCC$ bath applied ‘chromate conversion coating’ [technical term for alodine chemical film].... typically ‘clear to golden-yellowish’ in appearance. This film is micro-thin, soft and relatively easily removed with chemicals... so handle these rivets ‘gently’ to preserve the coating thru installation [bucking]... and they will survive several decades of service.

Anodize# is electrochemical build-up of a super-thin/tough and corrosion/heat-resistant aluminum oxide film... sealed ‘as anodized’ [‘grayish appearance’] or with colored dyes for various ID purposes [applied before/during finish sealing]. Anodize coatings are explicitly applied for enhance corrosion protection in a severe environment... or for color ID/coding... or for shop heat treatment... to be installed by the ‘ice-box method’.

4. D and DD rivets with gray ‘as-anodized’ finishes are capable of being solution heat treated, quenched then driven/bucked ‘as ice-box’ under rigorous conditions [sub-zero storage until driven] to preserve an unstable quenched-temper... ‘W’... that is capable of being deformed with ‘ease’... almost like annealed aluminum... then they naturally/spontaneously re-age to full strength [–T4] temper ‘in-place’ [~96-hours]... and still retain the benefit of the anodized finish which survives the high heat of solution HT/quench... for corrosion protection.

NOTE1.

A. Uniquely, D* rivets [CCC or anodized finish]... with practice, physical effort and sufficient capacity gun/bucking-bar... can be installed [bucked] satisfactorily in suitably ‘hard aluminum alloys’.

5. All other rivet alloys mentioned... A, AD, B, D*, K, KE... are intended to be driven ‘cold [as-is]’ since heat treatment is of no value-added... or would have a high likelihood of permanently 'destroying' the manufactured temper. Without strict process controls most of these alloys will rapidly change their metallurgy and begin uncontrolled migration to a ‘soft’ semi-annealed-state with high heat [as-noted]. Also...

All of these rivets ‘typically’ come with CCC finishes for ‘good-enough’ corrosion protection and lowest cost-per-rivet... or with[less commonly] anodized finishes for unique corrosion environments... with/without unique colors [special dyes] for ID/coding purposes... at significantly higher cost-per-rivet. Rivets with CCC and colored anodize finishes can be exposed to temperatures up-to ~250F-to-300F without damage to the alloy, CCC or dye-colored coating [short term]... but at/above that temperature(range) the CCC film and anodize color-dyes... are damaged by heat/oxidation and become washed-out and useless. .

NOTES2

B. FAA mandates special training for heat-treatment... including HT of rivets and similar parts.

C. IF You still want to apply high-heat to aluminum alloy rivets to soften them for ease of installation be aware that there are NO guarantees of useable strength/stiffness/durability and there would be a total loss of corrosion protection finishes setting them up for in-service corrosion.

D. On a side note, one homebuilt kit manufacturer is offering solid aluminum rivets NOT conforming with any known aircraft standard... their-own design/use... which in my humble opinion is mind-boggling dangerous and ill-advised... for aircraft use.

E. A warning that most are unaware of is that heat treating to –O [annealed temper] results in extreme low strength [expressed in PSI or KSI] ‘NOT TO EXCEED XXX’... means it can’t be any higher strength than XXX... and could be much lower strength than XXX and be ‘OK’ for annealed. For this very reason it is prohibited to use [heat-treatable-for-strength] aluminum alloys in ANY aircraft application... by all authorities [FAA, DoD, etc] and good-sense.

F. CCC, damaged by heat, is a corrosion time-bomb! A serious problem with 2xxx-T4 alloys [AD, D*, DD]... without applied corrosion protection... is a tendency for severe exfoliation corrosion.

G. Colored anodized, damaged by heat, is still OK for corrosion protection... but will lose their color ID [loss-of-value-added cost].

6. WARNING1.

I work at a DoD aircraft overhaul/repair depot... recently discovered that mechanics had installed hundreds of thousands of large diameter ‘AD’ rivets using non-standard riveting-methods resulting in +50% aberrant bucked-installs for ~10-years. After in-depth engineering review we realized that solid rivet installs are considered so self-evident and so standardized and so heavily trained into professional work forces... that discrepancies exceeding small percentages cannot be analyzed... simply never supposed-to-happen. For this reason we have no idea how bad the situation actually is... and it is now considered an ‘airworthiness crisis’ and rework [removal replacement of most/all of these solid rivets] is an urgent priority.

7. Conclusion... aircraft grade solid rivets are precision designed and manufactured ‘parts’ intended for specific strength and durability when installed properly in appropriate holes. Miss-use/abuse can render them worthless... IE dangerous. Use rivets as manufactured/designed and they will provide suitable/durable long-term service.

NOTES3.

H. I’ve been dealing with aircraft aluminum alloys and finishes*** [and their many fabrication processes] for +4-decades. I [mostly] understand the subtle permutations that make each alloy/temper/finish combination useful... or destructive... and how/why to alter these alloys/finishes for specific purposes... and importantly... when NOT to alter them. To me this is familiar territory... but I’m terrible at ‘splainin’ things. Hope this all makes sense.

*** And carbon steel and low alloy steel and stainless steel and magnesium and titanium and copper alloys and their suitable/applicable finishes [and their many fabrication processes]... and how everything fits/works together...

II. I have dozens of solid rivet installation ‘manuals/documents’... it is astonishing that there is a massive lack of consistency and explanation of their uses/do’s/don’ts across the board... so easy to use reliably... but so easy to screw-up.

J. There are unique ways to install rivets that I have ‘learned’ over decades... from the pros... that require training/practice to apply... that come in ‘handy’ when odd situations occur. Two classic examples of unique methods most are unfamiliar with is the ‘the NACA riveting method’... and ‘reverse bucking’... not to confused with each-other.

Sorry... Have-to-go... I wrote most of this reply during a company all-hands-telecon/meeting. I have a laundry-list of homebuiltairplaneforums.com threads I’d love to reply to... but too little available time to do so...

 

[wktaylor]

BBerson… just saw Your last post yesterday at 1230 PM...
I got some 6053 at rivetsinstock.com
Limited selection. They are almost as hard as "AD"
The 1100 are really too soft, but apparently the only choice for soft rivets. I was looking for something half between "AD" and "A".

These rivets are OBVIOUSLY NOT intended for aeronautical use... and in my experience are not worth 'betting Your/family/friends lives on'... for a host of reasons.

 

[BBerson]

These rivets are OBVIOUSLY NOT intended for aeronautical use... and in my experience are not worth 'betting Your/family/friends lives on'... for a host of reasons.

What is your experience with "these rivets". My experience is they are nearly as hard as "AD".
So, quite suitable for 6061 homebuilts. I would prefer somewhat softer.

 

[BBerson]

Many of you guys obviously know the chemistry and materials cross-referencing far better than I do... my first question is would there be some chemical or galvanic conflict between a standard AD airplane rivet and the 5052 material being riveted?

Second question is if the softer 1100 "nearly pure" aluminum rivets were used for this, could you simply reduce the rivet spacing or increase the rivet diameter to achieve the same level of tear-out, or shear, or tensile strength as you would have gotten if you had found 5052 rivets?

Yes of course I understand these suggestions are "making an end-run" around what would have obviously been the right way to do it, but if you are having this kind of trouble finding the correct rivets, even through Hanson and other large suppliers, then you may have to consider an end run.

These are choices for a designer. A limited skill kit builder should follow the plans normally.
1100 (A) rivets sold at Aircraft Spruce are only one third the strength of (AD). So would need three times the holes that could weaken the parts. A designer could design for this, but the 1100 are softer than needed.
My interest was more rivet selection. The (AD) is too hard for 6061 sheet and the 1100 (A) are too soft.

 

[Richard Roller]

Guuuuyyyys...

I want to caution everyone there are numerous misconceptions and miss-statements throughout this post. A few guys have made corrective statements... but not enough. And this starts with skittish’s presentation as to what rivets he was dealing with... ‘17-T4 really hard to drive’ with a raised dot.... which were probably purchased at a ‘bargain price’ surplus sale@... since they are rarely used anymore... except in antique/heavy jet [707, 727, DC-8, etc] structural repairs. @ on-a-dare, I will even bet that the label on the bag holding the rivets... if legible... indicates date of manufacture +25-years-ago.

In this case I would normally advise installing ‘B’ or ‘A’... or maybe ‘AD’... and NEVER mess with any heat treatment. OH by-the-way... I can’t figure-out WHAT finish was applied to the original rivets... and that has a large effect on this situation also.

Applying heat to these rivets for any purpose is a really bad idea... and in the long term You will not be happy with the results... even for the ‘non-aviation’ purposes described... “soften them so they can be installed ‘safely’ in 5052-O or –H32[?] aluminum sheet, tubes, etc.

Heat treating aluminum alloy rivets is as critical as heat treating aluminum parts: knowledge and hands-on training is essential.

1. First, let’s consider as-manufactured alloys solid rivets you are likely to use [specifications listed]

NASM20426 100-degree flush tension head [MS20426, was AN426]

NASM20470 protruding tension head [MS20426, was AN470]

NAS1097 100-degree flush shear [reduced-height] head

Alloy-code... head symbol... Alloy-temper... Finish

A... [none]... 1100-as forged.. CCC$

AD... depressed dot [dimple]... 2117-T4... CCC$ or Anodize#

B... raised cross [+]... 5056-H32... CCC$ or Anodize#

D... raised dot [tit/teat]... 2017-T4... CCC$ or Anodize#

DD... raised dash-dash [- -]... 2024-T4... Anodize# [only]

E... indented ring [o]... 7050-T73... CCC$ or Anodize#

KE... raised ring [o]... 7050-T73... CCC$ or Anodize#

3. How they are made.

High quality aluminum alloy wire per specification ASTM B318 [was] QQ-A-430] is fed into the cold heading machine coated with lubricant and are then forged/cut/rolled to a few standard shank lengths... 'shaped-blanks' of semi-finished size/length. These blanks have the rivet code symbol in the head... and may/may-not have the manufacturer's code-symbol [impressed, NOW or just before the finish is applied]

Formed ‘blank's are inspected’ for cracks, straightness, etc.

Heat treatable rivet alloys [AD, D, DD, K/KE] are heat treated to attain specified temper. Nondestructive testing and destructive testing validate the raw production lot.

The Blanks are then cut/trimmed to shank-length and other features added, as per purchase order.

Corrosion-protective finishes are applied, as required per purchase order... CCC$ or Anodize# ...

CCC$ bath applied ‘chromate conversion coating’ [technical term for alodine chemical film].... typically ‘clear to golden-yellowish’ in appearance. This film is micro-thin, soft and relatively easily removed with chemicals... so handle these rivets ‘gently’ to preserve the coating thru installation [bucking]... and they will survive several decades of service.

Anodize# is electrochemical build-up of a super-thin/tough and corrosion/heat-resistant aluminum oxide film... sealed ‘as anodized’ [‘grayish appearance’] or with colored dyes for various ID purposes [applied before/during finish sealing]. Anodize coatings are explicitly applied for enhance corrosion protection in a severe environment... or for color ID/coding... or for shop heat treatment... to be installed by the ‘ice-box method’.

4. D and DD rivets with gray ‘as-anodized’ finishes are capable of being solution heat treated, quenched then driven/bucked ‘as ice-box’ under rigorous conditions [sub-zero storage until driven] to preserve an unstable quenched-temper... ‘W’... that is capable of being deformed with ‘ease’... almost like annealed aluminum... then they naturally/spontaneously re-age to full strength [–T4] temper ‘in-place’ [~96-hours]... and still retain the benefit of the anodized finish which survives the high heat of solution HT/quench... for corrosion protection.

NOTE1.

A. Uniquely, D* rivets [CCC or anodized finish]... with practice, physical effort and sufficient capacity gun/bucking-bar... can be installed [bucked] satisfactorily in suitably ‘hard aluminum alloys’.

5. All other rivet alloys mentioned... A, AD, B, D*, K, KE... are intended to be driven ‘cold [as-is]’ since heat treatment is of no value-added... or would have a high likelihood of permanently 'destroying' the manufactured temper. Without strict process controls most of these alloys will rapidly change their metallurgy and begin uncontrolled migration to a ‘soft’ semi-annealed-state with high heat [as-noted]. Also...

All of these rivets ‘typically’ come with CCC finishes for ‘good-enough’ corrosion protection and lowest cost-per-rivet... or with[less commonly] anodized finishes for unique corrosion environments... with/without unique colors [special dyes] for ID/coding purposes... at significantly higher cost-per-rivet. Rivets with CCC and colored anodize finishes can be exposed to temperatures up-to ~250F-to-300F without damage to the alloy, CCC or dye-colored coating [short term]... but at/above that temperature(range) the CCC film and anodize color-dyes... are damaged by heat/oxidation and become washed-out and useless. .

NOTES2

B. FAA mandates special training for heat-treatment... including HT of rivets and similar parts.

C. IF You still want to apply high-heat to aluminum alloy rivets to soften them for ease of installation be aware that there are NO guarantees of useable strength/stiffness/durability and there would be a total loss of corrosion protection finishes setting them up for in-service corrosion.

D. On a side note, one homebuilt kit manufacturer is offering solid aluminum rivets NOT conforming with any known aircraft standard... their-own design/use... which in my humble opinion is mind-boggling dangerous and ill-advised... for aircraft use.

E. A warning that most are unaware of is that heat treating to –O [annealed temper] results in extreme low strength [expressed in PSI or KSI] ‘NOT TO EXCEED XXX’... means it can’t be any higher strength than XXX... and could be much lower strength than XXX and be ‘OK’ for annealed. For this very reason it is prohibited to use [heat-treatable-for-strength] aluminum alloys in ANY aircraft application... by all authorities [FAA, DoD, etc] and good-sense.

F. CCC, damaged by heat, is a corrosion time-bomb! A serious problem with 2xxx-T4 alloys [AD, D*, DD]... without applied corrosion protection... is a tendency for severe exfoliation corrosion.

G. Colored anodized, damaged by heat, is still OK for corrosion protection... but will lose their color ID [loss-of-value-added cost].

6. WARNING1.

I work at a DoD aircraft overhaul/repair depot... recently discovered that mechanics had installed hundreds of thousands of large diameter ‘AD’ rivets using non-standard riveting-methods resulting in +50% aberrant bucked-installs for ~10-years. After in-depth engineering review we realized that solid rivet installs are considered so self-evident and so standardized and so heavily trained into professional work forces... that discrepancies exceeding small percentages cannot be analyzed... simply never supposed-to-happen. For this reason we have no idea how bad the situation actually is... and it is now considered an ‘airworthiness crisis’ and rework [removal replacement of most/all of these solid rivets] is an urgent priority.

7. Conclusion... aircraft grade solid rivets are precision designed and manufactured ‘parts’ intended for specific strength and durability when installed properly in appropriate holes. Miss-use/abuse can render them worthless... IE dangerous. Use rivets as manufactured/designed and they will provide suitable/durable long-term service.

NOTES3.

H. I’ve been dealing with aircraft aluminum alloys and finishes*** [and their many fabrication processes] for +4-decades. I [mostly] understand the subtle permutations that make each alloy/temper/finish combination useful... or destructive... and how/why to alter these alloys/finishes for specific purposes... and importantly... when NOT to alter them. To me this is familiar territory... but I’m terrible at ‘splainin’ things. Hope this all makes sense.

*** And carbon steel and low alloy steel and stainless steel and magnesium and titanium and copper alloys and their suitable/applicable finishes [and their many fabrication processes]... and how everything fits/works together...

II. I have dozens of solid rivet installation ‘manuals/documents’... it is astonishing that there is a massive lack of consistency and explanation of their uses/do’s/don’ts across the board... so easy to use reliably... but so easy to screw-up.

J. There are unique ways to install rivets that I have ‘learned’ over decades... from the pros... that require training/practice to apply... that come in ‘handy’ when odd situations occur. Two classic examples of unique methods most are unfamiliar with is the ‘the NACA riveting method’... and ‘reverse bucking’... not to confused with each-other.

Sorry... Have-to-go... I wrote most of this reply during a company all-hands-telecon/meeting. I have a laundry-list of homebuiltairplaneforums.com threads I’d love to reply to... but too little available time to do so...

Lots of GOOD info here!

 

[wktaylor]

BB...
What is your experience with "these rivets". My experience is they are nearly as hard as "AD".
So, quite suitable for 6061 homebuilts. I would prefer somewhat softer.

Aircraft industry wide, and me... ZERO.

Did You/anyone 'ask' rivetsinstock.com folks for their blessing to use these particular rivets for aircraft structure installs... in writing?

What formal or even informal testing... strength, durability, corrosion resistance, installation consistency, etc [RE NASM1312]... has been done with these parts?

 

[BBerson]

No, homebuilders are not required to ask anyone for "blessing".Thousands of homebuilts are built with 5052 or steel commercial blind rivets. (Thorp, Heinz, Sonnex, etc.)
I have the data from Alcoa manual and FAA AC 43.13. that says use rivets slightly softer than base metal.

 

[wktaylor]

BB...

Hmmm 5052. ALCOA manual for commercial aluminum blind rivets??? Where'd you find it [book/document title?]... I love to get my hands on a copy!!!

Most aircraft grade aluminum [body] blind rivets are 5056, with some 2017 or 2219... and pin elements of similar alloys or 7075, steel or A286.

What about shear allowables for 6053 solids????

Commercial rivets tend to loosen tolerances for a generally good fit/performance/manufacturing-cost... for industrial [automotive, etc] use.

NOTE1.
Thorp, Heinz, Monnett are experienced engineers and would specify BRs with considerable experience and caution.

NOTE2
I never design to a blind rivet shear/tension 'ultimate'... I always design for structure ultimate... and ensure the BR load does NOT exceed BR YIELD load... in a nice tight hole.

 

[BBerson]

Alcoa Structural Handbook (1960)
Posted all about it in other thread here:Solid Rivet shop head size criteria

 

[skittish]

Thank you so much for your informative reply. My background (mech engineering) and experience(30 years in a fabrication shop) is certainly lacking the expertise required to make an informed decision. Really wish I could have spent some years with people who have contributed to this thread to gain a better understanding. I am very grateful to have posted the original question.
I have attached a photo of the rivets in Question. They are not 25 years old, they are probably 70 years old. I will not be using them for this project(or any other). Project requires about 2500 rivets.
Hopefully I won't open another can of worms, but is reverse bucking using a concave tool acceptable? The end product looks great but...

 

[wktaylor]

OK... Lets discuss the (a) Conventional riveting practices (b) NACA flush riveting method and the (c) the 'reverse bucking riveting' method. Hope this makes sense... my eyes are crossing...

1. All solid riveting is a two sided process... side-a, side-b... with a rivet gun driving a rivet set nose-piece and a matching-mass/weight bucking-bar.

Conventional riveting places a protruding head [brazier, semi-dome shape] or flush-head rivet [typically 100-Deg into a matched countersunk or dimpled recess] into position... and then the rivet-gun with a matching nose-piece... flush/flat face for flush-head rivets... or with an internal recess matched to the size/shape of the protruding rivet head... is set on the head... and a flat-surfaced bucking bar is placed solidly/squarely against the extended end of the tail/shank of the un-bucked rivet [~same mass/weight as the rivet gun + nose-piece + spring].

When the rivet gun is actuated the nosepiece applies rapid/controlled hammer-energy-pulses against the head... which is transferred thru the rivet shank to the bucking bar which causes the rivet shank to collapse and expand simultaneously... forging the rivet into the hole simultaneous to forming the bucked-tail ‘button head’. Ta-da... the rivet installation is complete.

2. The NACA Method driven flush rivet is very similar to conventional riveting, with the exception that a PROTRUDING HEAD rivet is used. The rivet is inserted with the protruding head placed on the side opposite of the countersink [or dimple-into-countersink]. The rivet gun with protruding head nosepiece [with a concave recess to match with the protruding/dome-head] is set into position on the manufactured rivet [protruding/dome] head... and the bucking bar is placed on the end of the rivet tail. When the rivet gun is actuated, the bucking bar collapses the shank/tail tightly into the countersink... while the rivet shank swells to fill the hole... and also leaves a slightly protruding button over the ‘now countersunk bucked-tail’... which is then milled/ground-off flush to the surface. After milling, the bare aluminum formed rivet tail is coated with CCC [see previous thread for CCC] for corrosion protection. NOTE this method typically requires use of ‘B’, ‘AD’ or heat-treated [Icebox] ‘D’ or ‘DD’ rivets... for the extra ductility to smoothly/tightly forge the shank-tail into the countersink/dimple.

3. Reverse bucking is a different animal all-together. In principle the rivet gun drives the rivet-tail to a button or into a countersink/button... while the bucking bar is held against the rivet head.

WARNING/HOWEVER the bucking-bar MUST have a suitable surface for the rivet head to drive/focus against!

Typically the rivet-gun nosepiece has a flush/flat, smooth/polished surface to bear on the end of the rivet tail.

Flush rivet heads need to ‘set’ onto a smooth/polished-surface on the bucking-bar... typically round, with a flat-to-slightly-crowned [convex shape] surface and rounded-off edges... to maintain/focus bearing-contact primarily with the flush rivet head... NOT the surrounding surface/structure. This can be an actual flush rivet set fastened to the bucking bar... or a smooth-machined/crowned driving anvil on the bucking bar surface.

Likewise a bucking bar used on a protruding/dome rivet head MUST have [a] a matching concave recess machined-into the bucking bar... or more preferably... a matching protruding head rivet set mounted tightly to the bucking-bar surface. This can be an actual protruding head rivet set fastened to the bucking bar... or a smooth-machined concave recess machined to fit the protruding head [style/size] on the bucking bar surface.

When reverse bucking the rivet, the bucking-bar must be carefully centered/aligned with the rivet head at the driving-surface/recess. The flush set on the rivet gun is firmly placed into position onto the rivet tail and the gun ‘triggered’ to crush the tail to swell the shank and form the button-head [or the button-head over-a flush/countersink install]. Milling the residual button off the countersunk tail is necessary... too shallow a button may indicate a shallow installation.

Riveting NOTES.

Some experienced riveters... with a sensitive ‘feel for the art of riveting’... can gently ‘twirl/swirl’ the bucking bar and/or the rivet gun to get a ‘tighter/neater’ overall seating of the bucked-tail, and head, regardless of process.

Good quality ductile rivets are essential to the process of riveting.

There are a breed of rivets that have no manufactured head... slug rivets... essentially just rivet shanks... that can installed by an experienced mechanic in protruding or flush applications.

Squeeze riveting is optional to bucked riveting... but is limited by ‘equipment accessibility’.

MIL-STD-403 PREPARATION FOR AND INSTALLATION OF RIVETS AND SCREWS, ROCKET, MISSILE, AND AIRFRAME STRUCTURES

MIL-STD-40007 RIVETS, SOLID, INSTALLATION OF

NASM47196 [MIL-R-47196] PREPARATION FOR AND INSTALLATION OF BUCK-TYPE RIVETS

FAA-H-8083-30 AVIATION MAINTENANCE TECHNICIAN HANDBOOK - GENERAL

FAA-H-8083-31 V1, V2 AVIATION MAINTENANCE TECHNICIAN HANDBOOK - AIRFRAME

AC43.13-1 ACCEPTABLE METHODS, TECHNIQUES, AND PRACTICES - AIRCRAFT INSPECTION AND REPAIR

 

[skittish]

Extremely informative. Thankyou for taking the time to respond to someone you don't know and will likely will never meet. Very much appreciated. I know this will be great information for a lot of others as well.