Solid Rivet shop head size criteria

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wktaylor

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184
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IF You have a countersunk hole... but no suitable/matching flush head rivet... what is a solution?

Use the NACA Method for rivet installation... original flush riveting technique... and often used for unique/odd/irregular countersinks.
Install MS20470AD rivet with head on interior... drive the manufactured head with gun/nose-piece**... buck the tail into the countersink [tail button must be 'high' after bucking]… microshave [mill] the tail flush to skin... apply brush alodine [no-rinse preferred] to bare aluminum... and try to apply a 'dab of primer' to the shaved/alodine flush head.

**IF access is restricted then install a protruding head 'set' from a 'squeeze-set' kit onto end of a bucking bar... and install a flush-riveting nose-piece into rivet gun... then carefully drive the tail into the countersink [tail button must be 'high' after bucking... and be cautious about gun-control to avoid skin damage]. Reverse bucking must be done VERY carefully.

NOTE. The 'NACA method', done carefully, produces 'superior' fatigue life at the countersinks... at the cost of extra time-experience-tools-corrosion control... which is why flush rivets were invented.

NOTE. Flush rivets of -7, -9 and -11 sizes are not normally available for oversize/repair... however protruding heads are potentially available.

NOTE. As far as I know, the NACA Method WILL NOT work for 'strictly dimpled' sheet metal Assy.

For any given rivet gun what is normal/nominal practice for selecting a suitable bucking bar?

FAA-H-8083-31 V1 has a very good discussion on riveting and includes a view of assorted/odd bucking bars for a variety of jobs/accessibility. I have seen far more bucking bar shapes designed for 'unique/restricted access'. However, the Hdbk discussion 'dances around' a key aspect of bucking bars... weight: too light and too heavy tend toward poor rivet installs. An old-timer taught me... and I've seen this referenced in a definitive riveting document 'somewhere'... that a good place to start is matching the bucking bar WEIGHT [mass] to the WEIGHT [mass] of the fully-assembled rivet gun, IE: with a specified nose piece, springs, keys, etc... 'ready to shoot'. Then test the set-up to get comfortable with it. There might be variations in bar weight for 'odd/irregular bars... but this is a good place to start. This set-up procedure was intended for pros installing a wide variety of rivets from -3s to -12s using different sized rivet guns needed for rivet sizes and alloys in production. In most cased -3s, -4s, -5s and -6s [typically Bs and ADs] can be driven with a relatively light gun and bar combo. A well-coordinated bar/gun set-up... as well-as focused attention... makes for almost effortless solid riveting.

NOTE. Other aspects of riveting/assembly, not discussed, are equally important...
… tight-fit between parts during drilling/riveting... using clamps and clecos...
… quality/sharp drill-bits and drilling techniques create clean minimally burred holes [and countersinks].
… etc.

CAUTION. Cheap/old/worn-out tools... drill motors/drill-bits, rivets guns/nose-pieces, bucking bars, etc... including pressurized shop-air and hoses... should be routinely repaired/maintained or discarded for smooth/efficient/clean working over the long-haul.

New rivet guns employ ergonomics, mechanics and vibration control so that operators can do these jobs safely/effectively for many years.

Obviously, the skills/odd tools for solid rivet installs is one of the reasons 'blind rivets' were developed... to avoid nightmare driven rivet installs.
 

gtae07

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Dec 13, 2012
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Location
Savannah, Georgia
I find that about 75% of the time (or more) bucking bar selection is driven by space available and access, not ideal weight. I tend to use the heaviest bar that I can properly and comfortably hold in place. I have favorite bars but can only use them about half the time.
 

Angusnofangus

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Sep 29, 2015
Messages
420
Location
Victoria, Canada
While on the subject of riveting, I thought I would throw this out. These rivet snaps, as you can see, are a little different than the garden variety one usually sees. Left to right are 1/8, 5/32, and 1/4. The 1/8 and the 1/4 were made that way, and a machinist friend turned down the 5/32 from a regular one. They definitely make riveting easier. My theory being that they concentrate the force better. A riveting buddy agreed with me that they make a difference.IMG_0001.JPG
 
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BBerson

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Easier in what way?
I suppose you mean it concentrates on the crown instead of digging the rivet head edge.
Looks to me like they were made for limited access heads.
 

Angusnofangus

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Victoria, Canada
Easier in what way?
I suppose you mean it concentrates on the crown instead of digging the rivet head edge.
Looks to me like they were made for limited access heads.
The force seems to be better concentrated, so the rivet goes down easier. The contact surface is exactly the same, and as noted, that particular 5/32 snap was made from a garden variety one. If one is digging into the edge of the rivet (called 'smiling' the rivet) then the gun and snap are not being held perpendicular to the rivet head, either that or using the wrong snap. And yes, they are handy for occasions when there might be something obstructing the rivet head.
 

BBerson

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I get occasional smiling on the rivet even if held perpendicular. It seems to be from moving around from side to side on the rivet.
None of my rivet snaps are exact fit on the rivet.
The rivet tape you suggested helps quite a bit but still nick some.
 

Angusnofangus

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Sep 29, 2015
Messages
420
Location
Victoria, Canada
I get occasional smiling on the rivet even if held perpendicular. It seems to be from moving around from side to side on the rivet.
None of my rivet snaps are exact fit on the rivet.
The rivet tape you suggested helps quite a bit but still nick some.
Not being securely on the rivet head will also cause a smile, if you bounce off you smiled the rivet. If you tear about three small pieces of masking tape and layer them on the business end of your rivet snap it helps a lot for not marking the rivet head. Just replace it every 20 or so rivets.
 
Joined
Feb 15, 2018
Messages
13
Location
Olathe, Ks.
IF You have a countersunk hole... but no suitable/matching flush head rivet... what is a solution?

Use the NACA Method for rivet installation... original flush riveting technique... and often used for unique/odd/irregular countersinks.
Install MS20470AD rivet with head on interior... drive the manufactured head with gun/nose-piece**... buck the tail into the countersink [tail button must be 'high' after bucking]… microshave [mill] the tail flush to skin... apply brush alodine [no-rinse preferred] to bare aluminum... and try to apply a 'dab of primer' to the shaved/alodine flush head.

**IF access is restricted then install a protruding head 'set' from a 'squeeze-set' kit onto end of a bucking bar... and install a flush-riveting nose-piece into rivet gun... then carefully drive the tail into the countersink [tail button must be 'high' after bucking... and be cautious about gun-control to avoid skin damage]. Reverse bucking must be done VERY carefully.

NOTE. The 'NACA method', done carefully, produces 'superior' fatigue life at the countersinks... at the cost of extra time-experience-tools-corrosion control... which is why flush rivets were invented.

NOTE. Flush rivets of -7, -9 and -11 sizes are not normally available for oversize/repair... however protruding heads are potentially available.

NOTE. As far as I know, the NACA Method WILL NOT work for 'strictly dimpled' sheet metal Assy.

For any given rivet gun what is normal/nominal practice for selecting a suitable bucking bar?

FAA-H-8083-31 V1 has a very good discussion on riveting and includes a view of assorted/odd bucking bars for a variety of jobs/accessibility. I have seen far more bucking bar shapes designed for 'unique/restricted access'. However, the Hdbk discussion 'dances around' a key aspect of bucking bars... weight: too light and too heavy tend toward poor rivet installs. An old-timer taught me... and I've seen this referenced in a definitive riveting document 'somewhere'... that a good place to start is matching the bucking bar WEIGHT [mass] to the WEIGHT [mass] of the fully-assembled rivet gun, IE: with a specified nose piece, springs, keys, etc... 'ready to shoot'. Then test the set-up to get comfortable with it. There might be variations in bar weight for 'odd/irregular bars... but this is a good place to start. This set-up procedure was intended for pros installing a wide variety of rivets from -3s to -12s using different sized rivet guns needed for rivet sizes and alloys in production. In most cased -3s, -4s, -5s and -6s [typically Bs and ADs] can be driven with a relatively light gun and bar combo. A well-coordinated bar/gun set-up... as well-as focused attention... makes for almost effortless solid riveting.

NOTE. Other aspects of riveting/assembly, not discussed, are equally important...
… tight-fit between parts during drilling/riveting... using clamps and clecos...
… quality/sharp drill-bits and drilling techniques create clean minimally burred holes [and countersinks].
… etc.

CAUTION. Cheap/old/worn-out tools... drill motors/drill-bits, rivets guns/nose-pieces, bucking bars, etc... including pressurized shop-air and hoses... should be routinely repaired/maintained or discarded for smooth/efficient/clean working over the long-haul.

New rivet guns employ ergonomics, mechanics and vibration control so that operators can do these jobs safely/effectively for many years.

Obviously, the skills/odd tools for solid rivet installs is one of the reasons 'blind rivets' were developed... to avoid nightmare driven rivet installs.

The NACA method of flush riveting is not used with conventional 100° or Briles 120° rivets. When I was still an active sheet metal mechanic, on DC-9/MD-80 series aircraft, we used the NACA method for the titanium finger doublers that was used in skin repairs. These were .012" to .020" thick doublers inside the skin. We would put the head side of the AN470 rivet on the doubler side and drive into the NACA 82° countersink on the outside of the skin. There were strict dimensions for the countersink depth and diameter, essentially the depth was 60% of material thickness. We would microshave the buck tail after it was driven. The “Aviation Technician Handbook – Airframe, vol. 1” has the basic information on page 4-46, 4-47. For the DC-9/MD-80 typical fuselage skin thickness of .050” we would use 5/32” rivets. Of course we were using the SRM for these aircraft, which I no longer have access to, so the dimensions might be slightly different from the FAA handbook I mentioned, but in the ball park.

Often we would shank drive the rivets due to access problems. It made no difference to the final rivet installation. Actually it was probably easier, as the riveter had a good view of the buck tail and whether the countersink was filled.
 
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TFF

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Apr 28, 2010
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12,860
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Memphis, TN
The secret of using cheap wire crimpers is not pinching yourself. Not that I know anything about it.
 
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wktaylor

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Sep 5, 2003
Messages
184
Location
Midwest USA
While on the subject of rivets...

Pop Quiz...

What aluminum alloy/type-code rivets can 'safely' be 're-hit' [re-bucked to adjust the tail] once installed?

What are the ID head markings for these rivets... ?
A [1100], AD [2117-T4], B [5056-H32, D [2017-T4], DD [2024-T4], KE or E [7050-T73]

Extra credit...

What 'other' solid rivet alloys are available... but are relatively uncommon for homebuilts?

What is the ID head marking for 6063-T61 [6053?] rivets?
 

BBerson

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Dec 16, 2007
Messages
13,126
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Port Townsend WA
I will just UPS one of those with each kit! Ha ha.
Actually, I now think only solid rivets will be done for subassemblies at the kit factory. The kit assembler will use only machine screws.
 
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