Glossary

It was brought to my attention recently that my blog is replete with technical jargon, and further, that I could increase my readership if only I included more stories about fluffy animals.

While it is necessary to use certain terminology to describe tools or processes unique to aviation fabrication, I am not completely insensitive to the concerns of my readership.  In order to make the material a little more accessible and a little less stodgy or monotonous, I've decided to punch it up a bit with a picture glossary illustrating few of the common tools used on this project.   Also, here is a Koala.

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Tools:

Cleco:

Used to temporarily hold thin items like sheet metal in place.  Clecos come in a variety of sizes which are color coded.  3/32, 1/8, 5/32, and 3/16 shown at right.

Pneumatic drill:
Same as an electric drill only lighter and spins at a much higher RPM.








Right angle pneumatic drill:
Air drill for tight confines.  The drill bits screw in with 1/4 threads.  Also very useful for deburing.








Uni-Bit:
A drill bit with multiple diameters.  Very useful for cutting thin materials, especially large diameter holes.







Rivet set:
The rivet set is the hammer end of a rivet gun.  The sets are replaceable to match the size and type of rivet being driven.  Left to right: back set, flush set,  straight 1/8 set, offset 3/32 set, and straight 3/32 set.






Rivet gun:

The rivet gun is the primary means of setting solid rivets.  It is used to hammer the head of the rivet with a die sized to the rivet  being set.  The other end of the rivet is pressed against a bucking bar.  The rivet gun pictured is a 3x gun which refers to the length the barrel and how hard the gun can hit.

Bucking bar:

The bucking bar is designed to provide a backstop against the force of the rivet being set.  They come in a various shapes and sizes, but they are essentially just a heavy piece of metal with one function:  To smash the rivet tail against while driving a rivet.  The heavier the bar the less momentum is transferred to your hand while riveting.  The bar in the lower right is a tungsten bar and is much heavier that is looks.  Placing tape on the bar helps reduce marring the skin or structure surrounding the rivet while bucking.

Pneumatic squeezer:

An alternative to driving rivets with a rivet gun.  The pneumatic squeezer works exactly the way it sounds.  It uses air pressure to squeeze a rivet instead of a hammer.  They have the advantage of highly repeatable results and they don't make a lot of noise.  Their principal disadvantage is that they can only reach rivets close to the edge of the structure.  No further in than the depth of the yoke.  The yoke is the black "U" shaped do-dad on the end of the squeezer at right.

Pull rivet tool:

The rivet pulling tool grabs the stem of a pull rivet and applies sufficient pressure to swell and deform the back end of the rivet against the work being joined.  When the tension on the stem is high enough to have completed this deformation, the stem breaks off of the rivet and can then be ejected from the tool.  A pneumatic puller on the left and a hand puller on the right.

Dimple die:

The dimple dies are used to put a... wait for it. Yes, dimple on the outside surface of a skin.   This allows a flush rivet to sit with its top surface even with the skin's surface much like a counter sunk screw.  Although the dimpling of the skins is a lot of extra work, the smooth surface that results is aesthetically pleasing and is guaranteed to produce, at a minimum,  a zero MPH increase in top speed.

Dimpler:

The dimple machine is used with dimple dies to press the dimples into the aluminum ribs or skins.

Scotch-Brite:

Scotch-Brite is the brand name of the miracle synthetic sandpaper by 3M.  Scotch-Brite is used primarily in two forms:  As a wheel attached a grinder or as pads used for manual sanding jobs.  The typical use for the wheel is for deburing sharp edges while the pads are mostly used for cleaning aluminum before priming or gluing.

Deburing tools:

There are quite a number of deburing tools available.  Shown at right are: a deburing tool for holes, double edge tool, and a single edge tool.  The hole deburing tool is use to clean up after drilling a hole, while the edge tools can take the sharp edges off of a straight cut piece or a large diameter hole.

Flaring tool:

There are a variety of tubes in an aircraft that must be joined to build a fuel, braking, or Pito/static system.  When ends of the metal tubing are joined in some kind of fitting, the tubes are expanded with an aircraft flaring tool.  The flared end mates with a complementary shaped end on the fitting making, one hopes, a gas tight connection. What makes an aircraft flaring tool different from the much less expensive and readily attainable automotive flaring tool? The automotive tool flares at a 45 degree angle while the aircraft tool flares to a clearly superior angle of 37 degrees.

Piloted Counter sinks:

There are probably as many counter sinks as there are drill bits. The most common used in this project is the piloted counter sink.  The pilot is the protuberance on the end which sets in the drilled hole to keep the counter sink going straight down.  This prevents wobble in the bit which would result in an out-of-round counter sink.  Besides cutting counter sinks, the piloted counter sink bit is also used for deburing.

Micro Stop cage:

The micro stop cage is attached to the business end of a drill and used with the piloted counter sink bits to provide an adjustable depth counter sink.  This allows the counter sinks to be uniformly cut to the exact depth for the rivet or screw being used.

Rivet gauge:

When a solid rivet is driven, the shop head is formed. A rivet gauge is used to measure its diameter.  The rivet is properly driven when the hole in the rivet gauge 'just' fits over the shop head.  On the other end is a "You must be this tall to ride the airplane" kind of height gauge for the shop head.

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Fasteners:

Solid rivet:

Most of the rivets used on the RV-7 aircraft are of the solid variety which means they must be driven with a rivet gun or mashed with a squeezer (hand or pneumatic).  The two types of rivets used in this project are the AN470 and AN426.  The AN470 is the classic dome topped rivet while the AN426 has a flat top for counter sunk application.  It is an interesting property of aluminum that the process of driving them, actually beating the hell out of them, makes them stronger (up to a point).  Just like the song, they are rivets named Sue.

Pull rivet:

Pull is the generic name for  "Pop" when speaking about rivets.  It turns out "Pop" is a brand name.  Who knew?  A few of the crankier old men in aviation can get pretty huffy if you call them Pop rivets. The pulling action of the rivet pulls a bead attached to the stem through the back of the hollow rivet forming the shop head.  When the tension on the stem gets high enough, indicating that the rivet has reached maximum clamping pressure, the stem breaks of with a "Pop."  Or should that be breaks off with a "Pull."

Pro Seal:

Pro Seal is an epoxy sealant that is impervious to aviation fuel after it has cured.  It is mixed at ratio of 10:1 by weight.  It also makes an excellent adhesive as it seems to stick to everything which also makes it extremely messy.  I suspect it would stick to running water given the chance.  At right, a battle scarred used container of Pro Seal pictured after sealing the fuel tanks.  The United Nations International Panel on Unpleasantness, IPU, has ranked Pro Seal just below cancer in its annual top ten list.

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Assembly processes:

Match drilling:

Match drilling is used to exactly match the location of a hole in two or more mating pieces.  An existing hole in one piece is used as a guide to drill through and into a mating piece.  The result is a hole in both pieces that exactly align in size and location.  A typical example would be the mating of a wing skin to a rib.  In this example case, the skin already has the hole located with an undersized diameter.  When the skin is placed over the rib, an undersized hole in the skin is drilled through to final size and at the same time also through the rib.  Now both pieces have a hole of the same size in the exact same relative location.  The purpose of match drilling is to maintain very high degree of accuracy

Deburring:

The necessity of removing burrs is that sharp edges are possible high stress areas that could precipitate stress fractures in the metal.  In addition, sharp edges make the metal dangerous to handle.

Dimpling:

Dimples are pressed into aluminum skins and underlying structure to allow for the use of counter sunk rivets, also known as "flush rivets."  When the depth of the dimple just matches the height of the head of a flush rivet, the top of the rivet will be even with the surrounding skin's surface.

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Terminology:

Shop head:

The head of a driven or squeezed rivet that was formed in the 'shop.'  This is the head which is at the opposite end of the rivet from the manufactured head.  In other words, the head which is formed from the rivet tail.

Manufactured head:

The head of a rivet as it comes from the rivet manufacturer.  Duh!

ANxxxx part numbers:

The AN prefix stands for Army/Navy.  A military part numbering scheme used for high quality hardware (think aviation grade bolts, nuts, screws, rivets...)

Empennage:
A fancy french word for the tail of an airplane.  The empennage usually consists of horizontal and vertical stabilizer plus a rudder and elevator.








Fuselage:
Another fancy French word.  The body of the airplane.  We really shouldn't allow the French to name our  airplane parts.

EFIS:
Electronic Flight Information System.  This is an acronym that is often used to refer to the PFD and/or MFD.  Look at that, I made and acronym joke.  The EFIS is simply the flight computer and instrumentation system.

MFD/PFD:
Multi Function Display.  Primary Flight Display.  On glass cockpit equipped aircraft, these are the monitors were the flight instrumentation is displayed.

#$%&:

One is likely to emit this imperative when a rivet is improperly driven and needs to be removed.  Its elocution is very important to relieving stress from the situation.  A loud clear voice seems to work best, and don't be forget to threaten the replacement rivet before you drive it.

#^&*   #^&*   #^&*! :  

Is the only rational response after being surprised that your finger was under there.  Remember, it's not your finger that hurts, it's the embarrassment of losing SA (Situational Awareness).  Feel free to add additional expletives as necessary.