Nuts & Bolts

Building BasicsIN AIRCRAFT CONSTRUCTION RIV-ETS are the primary fastenerused to connect two pieces ofmetal. A l u m i n u m rivets arelight, strong, and resistant tocorrosion. Their proper in-stallation is easy to check,and their failure is easy to de-tect dur ing a visual inspec-tion, and their installationhasn't changed much since WorldWar II. The rivet gun and buckingare still the process' primary tools.

In the last decade the aviationindus t ry has introduced severalnew rivet head styles and strongeralloys, especially for rivets used inbu i l d ing large a i r c r a f t . Becausehomebuilders might benefit fromthe new generation of rivets, we'lldiscuss them along with the tradi-tional styles.

Reading RivetsIn addition to making it easy to or-der rivets, their part numbers tellyou a lot about them. Here are a

A NewGeneration

The evolution of aircraft rivetsRONALD STERKENBURG

few examples of the more commonpar t numbers . Remember , AN(Army/Air Force-Navy) part num-bers are being superseded by mili-

In the last decadethe aviation indus-try has introducedseveral new rivethead styles andstronger alloys.

Alloy Code • AAlloy - 1100 or

3003 AluminumHead Marking - NoneShear Strength -10 KSINon-Structural Uses Only

Alloy Code - BAlloy - 5056 AluminumHead Marking •

Raised CrossShear Strength - 28 KSI

tary specification (or stan-dard) part numbers. For ex-ample, AN426AD3-4 is nowMS20426AD3-4.

Let's dissect this part num-ber: MS20470AD3-5. MSmeans military standard (orspecification). The number,20470, describes the headstyle; in this case it's a uni-

versal head. AD says the rivet ismade of an alloy (2117 Al) . Thelast two numbers give the diameterof the rivet's shank in 32nds of aninch and the shank's length (orreach) in 16ths of an inch. In thiscase, the rivet is 3/32 inch in diam-eter, and it's 5/16 inch long.

Let's try this one: NAS1097D5-7.NAS stands for National AerospaceStandard, the number, 1097, iden-tifies the rivet's head style (reducedcountersunk head), and the D saysit's made of an alloy (2017 Al). Thesame measurement standards ap-ply, so this rivet is 5/32 inch in di-ameter and it's 7/16 inch long.Rivet Types

Standard Head Types

Alloy Code - ADAlloy - 2117 AluminumHead Marking- DimpleShear Strength 30 KSI

Alloy Code - DAlloy - 2017 AluminumHead Marking -

Raised DotShear Strength - 38 KSI

100° FlushMS20426BACR15BA

UniversalMS20470BACR15BB

38 KSI When Driven As Received34 KSI When Re-Heat Treated

Reduced Head Types

Alloy Code - DDAlloy - 2024 AluminumHead Marking - Two BarsShear Strength - 41 KSIMust Be Driven in "W" Condition(Ice-Box)

Alloy Code - E, [KE'j "BoeiniAlloy - 7050 AluminumHead Marking •

Raised RingShear Strength-43 KSI

Replacement For DD RivetTo Be Driven in "T" Condition

Code UBoeing

BACR15CE

(Called Shearor

Skin Rivets)uNAS

NAS1097

Alloy Code - M '-̂Alloy - Monel \Head Marking •

None on Rush Head

82 MAY 2001

Two Dimples onUniversal Head

Shear Strength • 54 KSI

(Briles)

Modified 120°MS14218BACR15FV

Reduced UniversalBACR15FT

— -~-

1Length

—— I- in— 16ths.

Diameterin

32nds

One more: BACR15FVSKE5.BACR identifies a Boeing AerospaceCompany Rivet with an FV headstyle (modified 120-degree coun-t e r sunk head). This rivet has ashank diameter of 5 (5/32 inch),it's made of an alloy with the codeKE (7050 Al), and its length is 5(5/16 inch).

Rivet AlloyBecause it's relatively strong buteasy to drive, the AD—2117 al-loy—rivet is perhaps the mostcommon one in use today, andyou can identify it by the dimpleon its head.

The 2017 (D) and 2024 (DD)alloys are sometimes called ice-box rivets because you need toheat-treat them before you drivethem. These rivets wi l l remainsoft if you put them in a freezerafter the heat t rea tment . Oncethey warm up to room tempera-ture, you have approximately 15minutes to drive them.

One of the newer a l u m i n u mrivet alloys is 7050, and it's calledan E rivet or a KE rivet. The E rivetis 30 percent stronger than an ADrivet, a replacement for the DDrivet , and s t i l l relatively easy todrive with the rivet gun. You caniden t i fy an E rivet by the raisedring on its head.

Rivet HeadsThere are two types of rivet heads,protruding and flush.

The MS20470 universal (pro-truding) head rivet superseded theAN470 rivet, and it replaced the

flat head and brazier head riv-ets. Universa l head rivets arethe f irs t choice for all rivetingoperations. They come in sev-eral d i f f e r e n t a l loys, but themost commonly used alloy is2117 (AD).

The BACR15FT reduced uni-versal head rivet is similar in de-sign to a universal head rivet,but its head size is reduced tosave weight. It's available in sev-

eral d i f fe ren t alloys, but the alu-minum 7050 (E) alloy appears to bemost common because of its higherstrength. Note: You need a specialheader to install this rivet; if youuse a standard 20470 header, youwill damage the head of the rivet.

The MS20426, a 100-degreecountersunk (flush) head rivet, su-perseded the AN426 rivet, and it'sused where greater aerodynamicsmoothness is required. The in-

When you put yourheart and soul intoit, you need thefinest tools.The MetalAce English wheel benchmodel is perfect for home craftsmenwho want equipment that complementstheir skills.Rugged reliabilitycoupled with theutmost precision.Known bycraftsmen as thefinest brand.

MetalAce Bench 22B — Clamp it in a vise or mountit to a bench, it's capable of rolling features to thecenter of a 44-inch piece of material. Handles up to20 gauge steel or 3/32 of an inch aluminum. Weldedfloor stand and additional anvil wheels available.

Call now for a free catalog and see our complete lineof English wheels and related metal-shaping tools.

MetalflceE N G L I S H W H E E L S

Craftsmen know.Manufactured in the USA by Right Angle Tool • 1-800-828-20431-309-827-6878 • R.R. 3 • Box 305 • Bloomington, IL 61704

www.ratd.comFor more information, visit SPORT AVIATION on the Web at www eaa Ofg

Sport Aviation 83

wlding Basics

stalled shear strength of these riv-ets is lower t h a n un ive r sa l headrivets, and the most commonlyused a luminum alloy is 2117 (AD).

The N A S l o y ? KJO-dcgree re-duced countersunk rivet is s imi l a rin design to a regular countersunkrivet, hut the head si/c is reducedso that it can be installed in thin-ner sheet m a t e r i a l . This rivet isused in many modern a i r l iners .

The most common a l u m i n u m al-loys are 2117 (AD) and 2017 (D).These rivets sac r i f i ce c l amp-up( tens ion) s t rength for increasedshear strength.

The MSI4218 or BACR15FV is am o d i f i e d 120-dcgrec f l u s h headrivet. One of the more successfulnew rivet designs by Frank Brilcs,these rivets arc also called Brilcsrivets. They are used on the latest

Today's LASAR' engine control system is yourelectronic ticket to first-class flight performance:

• Easier starting, hot or cold, even with fouled or worn plugs• Smoother engine operation

• Reduced fuel consumption at cruise altitudes• Faster climb ratesLASAR combines the latest electronic technology and new features from four

years of flying experience. Vans Aircraft and DiamondAircraft fly their Textron Lycoming engines with LASAR's

upgrade, as do hundreds of Cessna, Piper, Mooney,and kit plane owners around the world. It was the first,and still is the only, FAA-PMA approved electroniccontrol system available. Isn't it time you experiencedthe perks of technologically

advanced performance?

For more information, call a LASAR distributor. Unison (815-965-4700),or visit our Web site at wwiAf.unisonindustries.com.

For more information, visit SPORT AVIATION on the Web at www.eaa.org

84 MAY 2001

generation of commercial aircraft.The counters ink well is counter-bored and then countersunk 120degrees, and a special set of coun-tersinking tools is required. The litand strength of these rivets are su-perior to the standard flush headr i v e t s . The most common a l u -minum alloy used is 7050 (E).

What Size Rivet?Among builders a frequent ques-tion is, What d iameter of r ive tshould 1 use, how long does it haveto be, and how far must it be fromthe edge (edge distance or r ive tpitch)? In general, the answers arefairly simple.

A rivet's shear strength (the forceneeded to shear or break it) de-pends (in large part) on its diame-ter, and in aircraft construction wetry to use r ive t s whose shearstrength approximately equals thehea r ing s t rength of the meta lsheets the rivets arc fastening.

Most people don't want to cal-culate bearing and shear strength,but a simple rule will help. To de-termine the rivet diameter, multi-ply the thickness of the thickestsheet times three and choose thenext larger rivet size.

For example, if you're going torivet a sheet of 0.032-inch and adoubler of 0.040-inch together,mult iply the thickest sheet timesthree (3 x 0.040 = 0.120) and choosethe next size of rivet. In this caseyou will select a 1/8-inch (0.125-inch) diameter or number 4 rivet.

The rivet hole should be per-fect ly round and approximate ly0.003-inch larger than the rivet di-ameter because the rivet expandswhen you drive it. There are over-sized rivets, which have the samehead size but a shank d iamete rthat is 1/64-inch larger. These riv-ets are an exce l len t choice fors l ight ly oversized holes (usual lycreated when you dril l out a lessthan perfectly driven standard sizerivet). For example an oversized

A, AD, B, DD Rivets

Pre-DriveProtrusion

FormedHeadDimension r

Minimum Preferred

D, E, (KE), M Rivets

Pre-DriveProtrusion

FormedHeadDimension

5/32-inch rivet will have the samehead size as the regular 5/32-inchr ive t , but i ts s h a n k diameter is11/64 inch. . . . .

When you place the rivetthrough both sheets, the shankshould protrude roughly 1.5 timesthe rivet's diameter. After you drivethe rivet (creating the shop head),it should protrude about half therivet's diameter.

Edge distance is the space be-tween the edge of the m a t e r i a land the center of the rivet hole.The minimum pitch is two timesthe r ive t ' s d i ame te r , but don'tmake it larger than four times therivet's diameter.

Rivet pitch is the distance be-

tween two rivets in the same row.The minimum pitch is three timesthe diameter, but four to six timesthe diameter is a safe approach.

Transverse pitch is the distancebetween two rivets in ad jacen trows. The minimum is 75 percentof the rivet pitch, but in manycases people select the same dis-tance for t ransverse pitch as forrivet pitch.

The one nice thing about build-ing a kit is that the manufacturerhas f igured these distances andspecified the rivets you should use.But learn ing about the d i f fe ren ttypes of rivets and their use is oneof the educational benefits of be-ing a homebuilder.

Cpckpit of the Future?

Get tomorrows glass cockpit today!Why spend thousands of dollars on an oldfashioned moving map system that you canonlyuseafewhoursaweek? ---•-•»--Anywhere Map is a unique system-usinginexpensive Pocket PC computers to give you anoutstanding moving map with:

Jt_- EFIS arc or HSI display• Exclusive Cones of Safety display-fly with

confidence night or day!Electronic AOPA Airport DirectoryWorld Wide DatabaseEasy Internet Database&SoftwareUpgradesTopography and terrain avoidanceE6B/Weight& Balance calculators • - •. •».*Electronic logbook & checklistsPersonal Digital Copilot-Flight managementsystem with reminders, alerts, and popupchecklists.

• AND, an everyday pocket computer withspreadsheets, email, address book,calculator, and more!!

Excellent mapping detail combine with valuable flightmanagement functions in a complete yoke-mountedsystem Written by pilots Anywhere offers featuresunavailable elsewhere, for maximum situationalawareness and ease of use. -K-

1-800-292-1160f.V www.controlvision.com

PO Box 596 Pitlsburg. KS 66762

Sport Aviation 85

A ^^^^* 1AnvdBlwherey T^kp pilotThe low cost color moving map that

gives you more