now we would like to move into one of
the topics for the aerospace world its
major the major one Ribbit's Ribbit's
are relatively low-cost permanently
installed fasteners that are lighter
weight than bolts they are interference
fit which makes them a lot different
from bolts when you analyze them or put
them in combination with other fasteners
and rivet installation is faster than
bolt installation because it can be done
in a lot of cases with automatic tools
ribbits worked the best in thin sheet
designs where shear is the dominant load
since a rivet really does not have very
good tensile properties tensile capacity
the rivets should also be designed to be
critical in bearing since you are
normally considering them as a big
pattern of fasteners holding a load so
since they have to work together they
need to be bearing critical so they can
distribute the loads properly the longer
the grip length of a rivet or that is
the total thickness of sheets being
joined the more difficult it becomes to
lock the rivet because you're trying to
compress all these sheets and sometimes
it's difficult to get them drawn up
properly
now even though rivets are designed with
an interference fit they're not airtight
or watertight so if you want to seal a
joint you have to apply some type of
sealant to the joint around the rivets
and here's another very important
feature since rivets are permanently
installed they have to be removed by
drilling or punching them out and
replace them with oversized rivets and
this is a real laborious task from the
standpoint of both getting the old rivet
out without screwing up the hold where
it's impossible to install another rivet
in it without going to a much larger
size which might get you in trouble an
edge distance and spacing and that type
of thing rivet materials are made of
various carbon steels corrosion
resistant steel brass aluminum Monello
titanium and they have to be ductile
enough that you can form a head on them
without cracking so you need a high
strength so it is a kind of a balancing
act to try to get one that's ductile
enough to form but on the other hand
will have a high enough strength to give
you the load carrying capacity that you
want now in the table 13 of course is a
list of some of the aerospace materials
and some of these rivets contain more
than one material that can actually come
up with a hybrid rivet and use a softer
material for the shop head so that you
can buck the thing in place and still
have a stronger shank
here is a list of the common ones of
course the the aircraft industry uses a
lot of the abs and DD is which are the
ms-20 four to six and two oh four seven
ho the the ADEs are used normally up to
a 5/32 diameter and they can be readily
formed at room temperature the the d DS
there if they're made out of 2024 they
have to be kept in an icebox until
you're ready to install them because you
can only cold work them when they're
down around zero degrees without
cracking them eleven hundred aluminum
that's usually non structural a fifty
fifty six is a special one in this
respect they're still used some people
are not aware I don't think that they
are stress corrosion sensitive and they
really should not be used in anything
other than a magnesium joint where
magnesium is more stress corrosion
sensitive than the 50:56 so therefore
the 50:56 will work out better we had a
case on the Atlas vehicle with fifty
fifty six rivets in which the heads were
popping off with the things that on the
pad but from stress corrosion so they
should not be used in most applications
now which is a 67 percent nickel and
thirty percent copper material is used a
lot for rivets because it is ductile and
yet it is higher strength than aluminum
and it's used for joining us stainless
steels titanium and canals copper is
usually used for non structural
applications the 70 50 T 73 that's the
one that is not sensitive to stress
corrosion is used it can be installed at
room temperature and it's used as an
alternate to the 2024 ice box rivet it
has almost as good as strength as
the 2024 and yet you don't have to worry
about carrying them around in an icebox
yes okay sorry about that
Jimmy go ahead all right we move on then
now that we got the microphone hooked up
properly we will move on to the head
types of Ribbit's now here are some of
the common head types that are used this
is not to say that somebody else can
have a one of their own because one of
the things that you find as different
manufacturers have their own ideas on
how to manufacture fasteners and so it
is hard to get total standardization
here is the the common ones of course or
the countersunk or flesh head are and
here is the flat that is used a lot now
of course if on the planes that the jet
planes normally have to have the flight
ribbits some of the older ones I know we
have a an old twin otter here I believe
that has the button head or flat head
rivets on it because it doesn't fly fast
enough to for the Greg to be that much
of a problem with the protruding rivets
moving on to the solid rivets which are
the ones usually used on skin
construction on airplanes they're a
little bit different from some of the
others so we'll cover them separately
here are the ones for construction and
and that is almost a thing of the past
using construction construction rivets
because welding has pretty much replaced
riveting in the construction industry
but anyway for the construction type
but they're usually larger diameters
5/16 through two inches and are made of
steel and they can't be installed coals
so they have to be preheated about 1,800
degrees now in the past all the bridges
that you saw had riveted lattice bars on
them in the old days you used four
angles and lattice bars to make your
main trust members for a through tres
tape bridge and the portal bracing on
across the top that's the part that
holds the two trusses together as a unit
was also riveted but on the newer
designs they use welded girders for that
so riveting is pretty much going out
with the times because of the labor cost
now if you're interested in construction
rivets they're still in ASTM spec ASTM a
502 covers construction rivets now for
aerospace usage of course you're talking
about small diameters here like 1/8
through a quarter of an inch and if you
remember on the drawings where you have
the ad like an ad 5 or something like
that called out with the little little X
it has the ad on the left-hand corner
and a 5 on the right-hand corner that is
a 5/32 ribbon and so a big gribbit in
the aerospace industry is 3/16 or 1/4
you just use millions of them so and of
course I had mentioned previously the
2020 44 ice box rivet and so since you
have to have both sides of a rivet
accessible sometimes you run into
problems trying to use solid rivets
because you have to have a bucking bar
on the manufactured head of the rivet
and a pneumatic hammer on the other end
in order to form a head
so that brings up the subject of blind
rivets blind rivets get their name from
the fact that they can be installed from
one side and in a lot of cases that's
the only thing you can can install so
they have this the following advantages
over solid rivets there is only one
Operator required the installation tool
is portable it's comparable to an
electric drill and size and you only
need one one side available for the
workpiece and you can use a variable
grip length with a lot of them you can
whereas with the solid rivets the grip
length is very critical on them in order
to head them you you can't go too long
or too short that's the part the grip
length is the part between sheets so
with the blind rivet they're more
adaptable the amount of pull that you
put on them you can have some variation
in the length of the shank itself the
installation time is lot faster than for
solid rivets the clamping force is more
uniform because you're pulling it with a
machine rather than two people looking
at it and saying okay this is enough and
you need less operator training OSHA
likes them better because they don't
make as much noise now getting into
specific blind rivets here is one call
it's a pole mandrel type operation and
you just simply shove it in the hole
from from the one side you have a
serrated stem that you clamp on to with
one part of the gun and the other the
head of it pushes against here to hold
it in place and then you just simply
pull the stem through when the proper
load is reached the stem is notched so
that it breaks off leaving you a fairly
flush head
now on a threaded stem rivet you have
pretty much the same thing except that
your stem is threaded and you thread it
through and we have one of those and a
couple of them in Figure 48 here are two
different types that you're actually
threading it through and you see the the
the goal on this is to pull it up tight
and form a shop head on this side by
expanding the tubular type body of the
rivet on in this case you are pulling
the thing up by compressing here by
pulling through by threading and you're
holding the hex there here is a drive
pin ribbit these are not used in the
aerospace world or in the industrial
world they're simple to install but
you're not sure just how they're turning
out because all you do is get them and
stick them in a hole and take a hammer
and pound that in and it expands it out
on this side to form a head and if
you're wanting to hold a couple pieces
of sheet metal together in your shop
that's fine but you don't trust them
that far with the airplane installations
here's another type of industrial rivet
a full tubular rivet and which you're
actually this has a hole in it you poke
it through and pound it and flare this
end out and form a head on that side
it's a weaker rivet than some of the
others because you see the wall
thickness right in there is not not that
much the semi tubular rivet is pretty
much the same thing except the hole is
not drilled in as far so you get more
solid shank in the hole which makes it a
little bit better now with all of these
one of the things you have to keep in
mind is they have to be done
pull so ductility goes up strength goes
down so this this rivet is not a very
strong rivet because if you made it very
strong then it would crack when you form
the head on it the the metal piercing
rivet is you actually grab it into the
second sheet and so so that one flares
out and creates a head like this on up
when you drive it through the sheet and
this one is okay for sheet metal
installations that type of thing but it
is not considered a structural type
rivet either and here's here's one that
goes back aways these have been around a
long time the old farmers use these to
repair harness and things of this nature
this is the split copper rivet and
although I couldn't find a picture of
the holder there's a little wire holder
that you put these in so that you don't
pound your hands with them and all you
do is lay the two pieces of leather down
and these things are fairly sharp on the
points and take a hammer and pound the
thing through the leather and once you
get it through then you get it spread
here and go ahead and pound a little
more and you clinch it and it holds
quite well on harness straps things of
that nature now here is everybody's
favorite for home use the pop rivet and
just to satisfy the people from Black
and Decker who wrote a nasty letter
about the fact that I hadn't changed
their name over to the association with
this because it used to be United shoe
that owned the company pop rivets our
blind rivets used for home repairs and
we mentioned earlier about the repairing
fenders of cars with duct tape that that
was a non structural type repair pop
rivets worked better because they have a
nail type stem which is gripped by a
handheld gun and you drill a hole
thing in pull it through with the stem
then the stem breaks off sometimes it
falls out all together and then you put
bondo over these to keep them from
rusting and sand them down and you got a
good repair job but they're they're not
a structural type that you would use on
an airplane here's an example of the
installation of a pop rivet where you
start out by poking the thing through
and this is bulb back here and so you
pull it through and expand it back here
and you have yourself a decent rivet to
hold a couple of pieces of sheet metal
together one of the things with these
that you've got to watch about though if
you are repairing aluminum gutters or
something that nature make sure that you
use the aluminum rivets rather than the
steel because then you get into the
galvanic corrosion problem and I
mentioned earlier you use steel rivets
there rest up like crazy in the aluminum
because of the galvanic corrosion so and
they do make aluminum pop rivets that
you can use on aluminum and the others
for steel now here's one that is a used
some in the I believe in the aerospace
world for secondary type structures it's
a rib nut made as far as I know it's
still made the BF Goodrich
it's a tubular rivet with internal
threads and you deform it in place to
kind of form a nut plate and if you look
at the next picture of one I think it
will show how you do it see it's it's
actually a a bolt if you will with a
threaded piece here you stick the thing
through a hole then you hold it up here
while you twist the threaded part of it
and actually pull this up and deform it
to where you get a installed nut plate
which then you can use to install
fasteners in
and those have been around for several
years and we haven't used them around
here but they are used some by people in
the industrial and I believe on
secondary aerospace structures okay for
the now for the the ad and DD rivets we
mentioned those earlier the fact that
those are the most common ones the most
preferred ones and one of the things
that I wanted to point out on this that
was called to my attention by one of the
guys from Lockheed Martin is that they
had had some problems on using rivets
that were not exactly the same material
as the skin because when you think of it
at 45,000 feet you have about minus
sixty-five temperature and on the runway
out in Phoenix you have about a hundred
and forty degrees on the skin so you
need to have rivets and skin that are
very close metallurgically in order to
prevent differential thermal loads and
they had had some trouble and had to
change to fasteners that were exactly
the same material as the skin in order
to get away from that the and the ice
box rivets I mentioned earlier are have
to be installed at zero degrees which
makes them not very popular the other
thing too you run into a problem with
them if you don't use a batch of them
you have to take them back if they've
been exposed to room temperature for
very long you have to take them back and
reheat treat them before and then cool
them down again before you can use them
so sometimes they've had trouble with
people short cutting things and oh well
they weren't out that long
so therefore we'll just go ahead and
reuse them and then they get rid of
cracking so so they're very hard to
control to make sure that you get a good
heading operation on them
the 50:56 I mentioned is stress
corrosion sensitive and all materials
except magnesium and now here's one of
the things too that is very important
solid rivets are expanded to an
interference fit so they should not be
used in composite materials because the
the hoop tension in the hole in a
composite material can cause
delamination of the material surfaces so
you should use a tight fit but non
expanding type rivet in composite
materials I had mentioned Mennella
rivets earlier
manal of course is 67 percent nickel and
30% copper it is stronger has a shear
element of 49 ksi and more heat
resistant than aluminum and yet it's
ductile enough to cold form without
cracking and they're used for joining a
stainless steel titanium and in canals
but it shouldn't be used for joining the
aluminum because it is way down in the
galvanic series compared to aluminum and
it also of course would have different
thermal expansion properties the
titanium columbium rivets this is a
hybrid one that is there well they
actually have have two types there's one
that they actually join two pieces
together I guess and this one is just
the the one that is part columbium and
they have a shear strength of 50 ksi but
they can be formed room temperature and
they're used for joining titanium and
aluminum because they they have enough
columbium in them to make them
compatible with aluminum and they
generally don't need to have the
corrosion protection on them except for
sealing in the hollow when you install
the rivet
now here is the table we showed earlier
on this so I won't go through it again
but just to let you know that these
these two are the ones you concentrate
the most on in the aircraft world now
here here's the cherry buck ribbit
that's the one I was thinking of it
actually has a friction welded piece of
soft titanium on it so that when you
form it that most of the harder stuff is
in the hole so you only have a little
bit of the softer material in the hole
so you get a higher overall strength
because this one has a shear strength up
to almost 95 ksi which is excellent and
they can be used up to 600 degrees and
they're available in both flesh and
protruding heads now cherry rivets are a
very popular one in fact they're almost
a generic although all fast and some of
the others would not want me to say that
about it since they make competing
rivets but cherry rivet is a blind rivet
with a locking collar and you have a
pull stem on it but it is a better
structural rivet because they have
better materials in it then then say a
pop rivet would have they're also
available in oversized diameters where
if you have if you have to replace a
rivet of course when you drill the hole
drill the old rivet out then you have to
ream the hole to get it prepared better
and that takes enough material off of it
that you can't get an interference fit
so you have to use an oversized rivet so
they make specific oversized rivets and
given sizes I forget know how many
thousands they are over
sighs but they they will fit a reworked
poll they have shear strengths
comparable to the the ad solid aluminum
rivets and they're used a lot on
secondary structures but they're not
used on primary structure you normally
use the solid rivets on primary
structure in an airplane now note that
all of these blind rivets along with cut
can all fast is restricted by the
guidelines here's an EM aspect that
tells you how you should use them and
there's the statement also about the
secondary structures versus primary here
is the part of a installation in which
you have the gun here that holds the
head in place then you start the process
of pulling the stand through to expand
it if you go on to the next figure you
have the completed installation there's
a little locking collar this is the part
that's shown in black tier that comes in
and is pushed in around the shank after
you have broken it off which gives you a
good seal on it to make sure that the
stem stays in place on it now here is a
table of cherry rivet materials and
notice that the the stem and the sleeve
are not different materials because the
stem has to be strong to pull through
and deform the sleeve the sleeve has to
be ductile enough to farm without
cracking so you have so so the strength
of the rivet is a combination of those
two materials so like here if you have
the 5055 a looming it with alloy steel
minal with stainless steel and here's
inconel 600 with an Inc and LX 750 pull
stem on it and look at the you can kick
the temperature way up by going to the
temperature resistant nipple stainless
now Huck is also one of the big
suppliers of rivets there's are similar
to cherry in fact if you look in mill
handbook five for rivet allowables there
are a lot of men there and I know on in
our fastener Task Group one of the
things we have argued and fought over
there is trying to come up with
allowables
that will include all of these
manufacturers under one heading so that
we won't have trouble with somebody
saying hi and you're favoring our
company versus company X and so on so
you have to come up with a generic table
to give allowables for this type of
ribbon so that it uncover Huck and
cherry and all fast now move on to the
next figure and we'll look at a standard
Huck gribbit to see this is this is
pretty much similar the other one except
and in this case you're compressing the
sleeve a little bit this way but the the
principle is still the same you have a
locking collar you have a serrated pin
that you pull through and then when
after you pulled it through it's not
chair so that it breaks off and you have
the complete completed rivet
installation
now the here is a Huck Clint rivet which
is a little bit different it has a
separate sleeve here that compresses
inside when you pull the thing through
and kind of gives you a seal on it that
one I'm not sure how widely used it is
by the aerospace companies I did not get
a benchmark on it from any of the
companies prior to this course now all
fast makes several types both solid and
blind and their wire draw rivet has a
tapered stem bulb and so that it expands
the tubular body which is a little bit
different than the the regular cherry
and Huck so you see this one I guess it
shows up better over here this is
actually tapered so that it it pulls
through and keeps expanding as the
poster whereas the other one was a solid
tape but the the final installation
there is the same because you wind up
with a the thing pulled through to
expand it and then you have the locking
collar around the stem at just inboard
of where it broke now high shear makes
other types of rivets and one of the
ones that they make is a high-strength
stem with a swage collar that you put on
it and over and this one if the collar
is size such that you can look at it
from the outside and inspect it to tell
whether it was installed properly so if
you turn to figure 61 this is a high
shear installation this is usually a 20
20 44 collar and you just pull the thing
through Suede's it on here
and the way that it's wages on you can
look around the top of it here and see
whether it was farmed properly so that
it can be inspected from that side now
this is not a an expanding rivet that's
the difference this one these are used a
lot for installing brackets that are
structural type things to heavy frames
and so on in planes where you want a
real good fastener but you'd rather not
use bolts and nuts because you can get a
these these would be installed in a
drilled and reading hole so it would
give you a tighter tolerance on now lock
bolts are also commonly used and they
are a non expanding high-strength
fastener that has either a suede scholar
a threaded Collard to lock them in place
it's a variation of the high fear that I
just showed you they're accepted in this
case you normally have a have a stem
that you compress the collar on a lock
bolt is similar to a rivet in one
respect it's hard to remove once you
install it and it's not very strong in
tension because once again it's a
metallurgical balancing act you want the
collar to farm but on the other hand it
can't crack so it can't be nearly as
strong as the shank so what you have is
a fastener which is very strong and
shear but is weak in tension so normally
you try to design them such that they're
not in tension now they're difficult to
inspect so if it's something that you
need to have a more positive lock on you
should look for a bolt nut assembly but
they're fast in style and on the next
page is one type of lock bolt this is a
Joe Bolt and what you have here the
locking sleeve their collar is expanded
to form a shop head because you're
rotating the stem in a gun and holding
the hex head in place so you're running
this through a threaded year to expand
the sleeve to form a head then the the
stem is not so that when you reach the
proper torque it breaks off
now the the Huck bolt is a one with the
serrations on the shank rather than
threads and it's switched in place and
the one thing about them since you don't
have threads they can't back off because
you just have straight serrations so
they're used a lot in the trucking
industry for putting truck bodies
together because they're available in
fairly large diameters you can get up up
to about a half inch diameter on them
and of course they're very good in
fatigue because once you put them
together and clamp the collar on they
can't come loose very well unless the
collar would actually break and they're
available in carbon steel stainless
steel and aluminum and on the next page
is Huck bolt installed and you see what
what they have is a notched stem you
pull the thing in place
there's your unser rated shank that you
put in the joint and then it breaks off
once the thing is that the collar is
switched in place now high fear makes a
high lock which is a similar one and
it's it has to be fed through a hole
from the fire side and held with a key
to prevent rotation while the about is
being torqued with a tool then the outer
portion of the nut breaks off on this
one now the high locks are available in
super high strength materials the alloy
steel h-11 tool steel stainless steel
and titanium now one of the things I
wanted to call your attention here
though the h-11 tool steel which has
been used in the past by SPS for a lot
of their super high strength bolts it is
stress corrosion sensitive and some of
the companies have kind of backed off on
using it or using it in the real
high-strength see this hundred and
fifty-six ksi here that is
if you that's about a 260 heat-treat
bolt so the elongation gets pretty low
on it and if it's stress corrosion
sensitive then you have to really do a
good job of protecting it in order to
assure yourself you're not gonna have
some problems now here is a high lock
installation now this is threaded on so
the the threaded diameter is a little
bit smaller here so that you can slide
it through from the backside without
screwing up the threads then you hold it
it has a internal hex in it so you put a
key in it with the gun to hold it in
place then tighten it down the outer
part of the nut that you're talking with
breaks off when you reach the proper
torque now here is an unusual one the
Hyatt Teague is a high lock which is
actually driven into an interference fit
hole before the color is installed and
of course because you have the threads
are slightly smaller you can do this
then of course the interference fit
increases the fatigue resistance and it
actually will hold it in place while you
are tightening it down and I don't have
a picture of one of them with this
the taper lock is made by SPS and it has
a threaded stem tapered shank and it's
installed with an interference fit in a
drilled and reamed hold now the tapered
shank is that's only a 1 and don't ask
me how this becomes a critical thing
it's a 1.19 degree taper that has on the
sides and you lubricate the shank so you
don't have to do anything as the hole
you just drive the thing in but this
interference fit keeps it from rotating
while the lock nut with a captive washer
attached to it is installed and there is
a picture one of them in the next figure
so you have this is kind of showing this
way although it in reality it isn't in
in steps that much you would not be able
to see the steps on it do that slight
angle but then you install it with this
this nut on it and you can sense it's
driven in place if the friction will
hold it while you're installing the net
now next here is an eddy bolt and
they're used a lot by Boeing in the
airplane business
I understand they use millions of Monday
777s 747s and so on
and it's kind of an oddball in my
opinion it has a deformed threads such
that it that you use a kind of a socket
type head that deforms to the point that
it starts slipping and then you know
that you it is installed properly so be
easier just to go with the picture on
the next page maybe I guess the better
with this one this one has a fluted
threads on the stem here you can see it
and so you start out you have a nut that
has these protrusions on it and you have
a special wrench to fit on that so you
tighten the doggone thing until the nut
deforms to where these protrusions push
it in and it pushes in and locks on
these flutes here and then when you
start spinning you know you have a the
proper installation which is kind of
strange but they work then they have
another tape that has a swags color like
the the ones that the lock bolts that
I've been showing you and on that one of
course you need a bucking bar on the
back of it to hold it in place because
you're actually pushing down here and
deforming the collar around it but the
locking is the same it still has this
type of shank on this shank is the same
as this one and those are used
extensively and they're fairly new
they've only been around for a few years
now here's remember earlier I mentioned
that you don't want to use solid rivets
in the composite material
fiberglass reinforced plastics this type
of thing and all because it will start
unraveling at the surfaces well here is
one made specifically for composite
materials it is a titanium lock bolt and
instead of it has a hundred and thirty
degree head on it because you don't want
the counters thank you very much on them
because you want to avoid the grinding
on the surfaces as much as possible
because of the reinforcing fibers so so
this is a very flat big head that they
have on them and that gives smaller
contact stresses on the composite
surfaces it's it's it's a tight fit but
not an interference fit then they have a
different type of serration on them that
they have a 20 degree angle here instead
at 20 and 40 rather than the 30 30 that
you would normally have on a nut on the
serrations to give you better holding
power because now with this flatter
angle here you can when you put the
collar in place it's harder to pull it
off because you're trying to pull
against that angle when you install the
thing and here is one of them installed
and now see see notice that how odd this
head looks because it's 130 degrees
instead of 82 or 100 most of the
aerospace stuff is 100 degree
countersunk head and then see the it's a
installed very similar to the rest of
the lock bolts and stuff like that it's
a color that is pushed in here you have
a pole stem that breaks off when you've
reached the proper load on them
I believe monogrammed fasteners is the
outfit that makes that one out of was
there one of the companies out of
California so general guidelines for
selecting rivets and lock bolts don't
use expanding rivets and composites as
we've talked about here
don't use 50:56 aluminum rivets and
anything other than magnesium since the
50:56 a stress corrosion sensitive a
threaded lock bolt that's one of the
ones that has the nut on it to actually
threads on and then breaks off the outer
portion of it can carry up to the
tensile allowable of the shank but each
design should be checked individually
and since drilled fastener holes are not
plated or coated it's necessary to use
some type of sealant over the raw
material surfaces to retire to prevent
galvanic corrosion between the fastener
in the joint material and of course you
can find lots of information on joints
and rivet allowables which were
determined by tests and mill handbook 5
I think it's chapter 9 the mill handbook
5 has a all these joint allowables
rivets
they cover they give you a table of
rivet in a given thickness of material
how much it'll carry in here they even
show the knife edge cut off so remember
I talked about the knife edges yesterday
to avoid they show where you cut it off
to make sure you don't get knife edges
and all that type of thing ribbon
installations are covered by mil
standard 403 some corrosion prevention
methods are covered by these two mill
specs design and selection requirements
for blind structural rivets are given
that ms 33 5 22 and testing of fasteners
is covered in mil standard 13 12 that is
a huge document which I will at
the end somewhere along the line I have
a listing of all the different tests
that are covered in that document it's a
whole three-ring notebook of standards
for the different testings I think 30
Sims sections or something like that
then this Naas 5:23 gives ribbit codes
and call-outs that's the one the covers
I believe the little X with the
different designations on it for how to
call out a specific ribbit on a drawing
whether it's counter something years I
had person I'd know that business and
then one of the other important things
review the fastener manufacturers design
criteria before incorporating his
fasteners into your design and that's
one of the things that day for Trek I
found out call the manufacturer and find
out what his fasteners sell for before
you decide that you're going to use a
few hundred of money or designed because
they can get expensive particularly in
small quantities now moving on to
inspection and acceptance of fasteners
this is one of the things that is not
covered very well by most people because
we can specify all the things that we
want in fasteners and but when we get
them we don't necessarily get what we
ordered and the the criticality of the
fastener design should determine how
much inspection we have on it so we'll
cover some of the inspection methods
that are used now on ordinary fasteners
bolts nuts and stuff like that we can
use hardness testing as a that's a
simple one you use
Brunell tests for aluminum usually and
rockwell for steel
and the what what these in general do
you have a little ball that gives you an
indentation and the amount of
indentation that you get is correlated
to the hardness of the material and that
in turn to the strength of the material
so for example if you go to a table rock
and see a great eight fastener is about
a rock well thirty c-33 I believe and at
least it gives you some indications and
there that's an easy test to run because
you have a little machine you just slap
the thing in there run the test or at
least a beginning test on it the Brinell
is used for testing their aluminum stuff
usually although Brunel and Rockwell can
be correlated because Wilson company
makes all this equipment and they put
out tables that give you the correlation
between them you also have a Rockwell B
scale for medium hardness materials
usually your your carbon Steel's are
rated on the the B scale and then when
you get up I think a a B 100 is
equivalent to around a C 18 or 20 or
something like that for the harder
materials so if we go to the next figure
here's a Brinell hardness tester and
what you have is a little table that you
put your sample on the ball is in the
headgear and you actuate the thing this
one this is an older one I think when
you just use a handle to actuate it
nowadays it probably on these they
probably make them that if there are
electronically actuated that one is for
the aluminum and then here is the Iraq
well this is one of the newer Rockwell
models that got out of one of their
catalogs or Wilson catalog same thing
you have a headgear to put your sample
on or platform and then you have the the
ball as in this part of it you program
the thing to give you
given amount of load and it measures the
indentation and gives you a reading
which you can use with the table to
check it out
this mil standard 1312 de 6 gives a
standard pest method and specifies the
apparatus to be used for hardness
testing and all types of structural
fasteners now the the B scale this is
the the size diameter ball and the the
load you to use with it and then the C
has has its own diameter and and the
load and here's another one a Rockwell
superficial hardness tester except the
indentation is smaller and then new and
Vickers micro hardness testers some of
these they have them small enough that
you can actually take them out on the
job and test your parts without having
to pull them out and take take them into
the shop you may metallurgical lab to
get them checked now for fastener
hardness testing one of the problems you
run into of course is how do you get an
accurate reading and if you have cold
work the fastener and farming it if you
take a reading on the outside someplace
it may not necessarily be the proper
strength so to get accurate readings you
need to get core hardness so you can you
can take a machine it down and get two
flat parallel surfaces and use one of
them for hardness testing and the other
thing you could do if you have small
fasteners that you can't do that with
then you can mount them and the these
metallurgical people can put them in a
nice little thermoplastic type setting
that you can then put it on the platform
and get hardness testing and the the
beauty of that is since you can't get
through hardening in a fastener and a
lot of materials above about
three-quarter inch diameter so you need
to take both hardness readings close to
the threads and at the core to see
whether you're getting the true strength
indication for the fastener so sew on
the little ones this is a zero door
number five so that's 60 to 60
thousandths to 1/8 diameter and in same
thing for rivets you can set those and
then on larger ones you can get there is
a way of measuring the shank if it's not
cowork too much that you can get a
ballpark tape reading if the thing is
big enough but this is not a very
accurate reading it's only if you're
looking something just a general type
reading now tensile testing this is
something of course you can do and that
they do a little bit of that around here
curl Bergquist is the guy that does it
on taking a few samples out of the greed
eights and socket head cap screws and
pulling them just to see what they are
good for so in general you take a few
out run them if any of them fails you
reject the light and what you do is you
use a regular tensile testing machine
that has large enough fixtures that you
get essentially no deformation from the
fixtures themselves because you want all
the deformation to be in the fastener
that way you can even measure the yield
holder but strength any long Gatien
here's another test that can be used and
of course counterfeit fasteners most of
the time are made by cheating on the
carbon content in order to heat treat a
fastener and and we have in the
specifications for a alloy steel
fastener it has to be a minimum of 28
points of carbon in order to get heat
treating and usually you use them up
around 40
so the counterfeiters can add boron
increases the harden ability of steel
and boron is cheap and you don't need
very much of it to add so you can take
1020 steel and add little boron to it
and heat-treated
so one of the tests that is used on
acceptance of alloy steel fasteners is a
carbon content test and there's
different ways of doing it one of the
company that I believe makes the
equipment that we have around here is
called Li CO and what you have is some
type of a furnace in which you it's even
either an induction or high-frequency
type a resistance type furnaces and you
take a little chunk of this stuff and
put enough oxygen in with it that you
can burn it and then you have different
ways of measuring by getting the carbon
dioxide from the combustion you can
measure it and get the carbon content
out of your sample so I'll kind of go
into this and a little bit more detail
here for a couple minutes yet it's high
temperature combustion and you have two
types of furnaces a high frequency and
resistance high temperature and you use
two different methods of carbon sulfur
detection infrared absorption and
thermal conductivity are the two
different methods that are used for it
the the test theory of course is to
determine the content of carbon and
sulfur and you can separate them out and
find out which is which and the so that
you get carbon dioxide and sulfur
dioxide and so with this furnace you
take it you have to take it up to a
pretty high temperature even with the
oxygen to burn the carbon off of the
steel because steel doesn't burn very
well
the other oxide compounds that you get
during this combustion you can siphon
them off and get them out and you also
remove the moisture with some sort of a
diskant such as Herald even put in there
what to use magnesium perchlorate Carol
Casper helped me on coming up with all
of this stuff the samples here's one of
the important thing you have to make
sure that you know exactly how much
weight you have in your sample in order
to do the testing because what you're
looking at is the carbon per late in it
and since it's such a small amount the
the weight of the sample has to be
accurate the limitations on it also the
specimens must be homogeneous in other
words if you spoke of the
decarburization if you had say heavy
content of carbon in the surface of the
thing due to the way it was heat treated
then you would get an erroneous reading
it would show that it had a higher
carbon content then it really had
throughout graphite bearing specimens
you have trouble with in other words you
can't have graphite on the outside for
the lubricant and of course the method
is destructive so getting a sample and
weighing it is a fairly short thing and
then you have the high frequency
furnaces that to use is it actually has
a coil a heating coil on it and you have
a a ceramic crucible that holds the
sample and you heat it up and cook it
out and here's one of them on the next
page then we will take a break and we
look at it when we come back