 Now we would like to move into one of the topics for the aerospace world. It's the major one, rivets. Rivets 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. Rivets work 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 are 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 are 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 is another very important feature, since rivets are permanently installed, they have to be removed by drilling or punching them out and replacing 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 in edge distance and spacing and that type of thing. Rivet materials are made of various carbon steels, corrosion resistant steel, brass, aluminum, mannell, 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 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 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 aircraft industry uses a lot of the ADs and DDs which are the MS20426 and 20470. The ADs are used normally up to a 530 seconds diameter and they can be readily formed at room temperature. The DDs, if they are made out of 2024 they have to be kept in an ice box until you are ready to install them because you can only cold work them when they are down around zero degrees without cracking them. 1100 aluminum that's usually non-structural. A 5056 is a special one in this respect. They are 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 5056. So therefore the 5056 will work out better. We had a case on the Atlas vehicle with 5056 rivets in which the heads were popping off with the things sitting on the pad from stress corrosion so they should not be used in most applications. Menel which is a 67% nickel and 30% 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 stainless steels, titanium and incanels. Copper is usually used for non-structural applications. The 7050 T73 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 strength as the 2024 and yet you don't have to worry about carrying them around in an ice box. Yes. Oh, it wasn't, is it, is it picking me up? Yeah, it's picking me up and it's picking my tie up too. Oh, it's picking the tie up too? Okay, well then we'll have to. Okay, sorry about that. Do you want me to 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 rivets. Now here are some of the common head tapes that are used. This is not to say that somebody else can have one of their own because one of the things that you find is different manufacturers have their own ideas on how to manufacture fasteners. And so it's hard to get total standardization. Here is the common ones, of course, or the countersunk or flesh head. And here is the flat that is used a lot. Now, of course, on the planes that the jet planes normally have to have the flesh rivets, some of the older ones. I know we have an old twin otter here, I believe, that has the button head or flathead rivets on it because it doesn't fly fast enough for the drag 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 that is almost a thing of the past using construction rivets because welding has pretty much replaced riveting in the construction industry. But anyway, for the construction type rivets, they're usually larger diameters, 5-16-2 inches, and are made of steel, and they can't be installed cold, so they have to be preheated to about 1800 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 truss members for a three-truss type bridge. And the portal bracing 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 has pretty much gone out with the times because of the labor costs. Now, if you're interested in construction rivets, there's still an ASTM spec, ASTM A502 covers construction rivets. Now, for aerospace usage, of course, you're talking about small diameters here, like an eighth 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 x, it has the AD on the left-hand corner and a 5 on the right-hand corner, that is a 5-30 seconds rivet. And so a big rivet in the aerospace industry is three sixteenths or a quarter. You just use millions of them. So, and of course, I had mentioned previously the 2024 T4 icebox 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 the following advantages over solid rivets. There's only one operator required. The installation tool is portable. It's comparable to an electric drill in size, and you only need 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 hit them. 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 a 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 called a pull mandrel type operation. And you just simply shove it in the hole from the one side. You have a serrated stem that you clamp onto 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 in our couple of them in figure 48. Here are two different types that you're actually threading it through. And you see 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. 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 rivet. 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 make 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 of pieces of sheet metal together in your shop, that's fine but you don't trust them that far with the airplane installations. Here is another type of industrial rivet, a full tubular rivet in 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 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 ductile. So ductility goes up, strength goes down. So this rivet is not a very strong rivet because if you made it very strong then it would crack when you formed a head on it. The metal piercing rivet is, you actually drive it into the second sheet and so that one flares out and creates a head like this on it 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 is one that goes back a ways. These have been around a long time. The old farmers used 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 was 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 clench 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 are bland rivets used for home repairs. And we mentioned earlier about the repairing fenders of cars with duct tape that was a non-structural type repair. Pop rivets work better because they have a nail-type stem which is gripped by a handheld gun and you drill a hole, stick the 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've got a good repair job. But 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 bulged back here. And so you pull it through and expand it back here and you have yourself a decent rivet to hold a couple 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 of that nature, make sure that you use the aluminum rivets rather than the steel because then you get into the galvanic corrosion problem that I mentioned earlier. You use steel rivets that rust up like crazy in the aluminum because of the galvanic corrosion. 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 sum in the, I believe in the aerospace world for secondary type structures. It's a riv nut. As far as I know it still may be a good rich. 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. It's actually 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 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 65 temperature and on the runway out in Phoenix you have about 140 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. And the icebox rivets I mentioned earlier 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 oven you have to take them back, if they have 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 rivet cracking. 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 in 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 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 Manel rivets earlier. Manel of course is 67% nickel and 30% copper. It is stronger, it has a shear ultimate 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 stainless steel, titanium and incanels, but it shouldn't be used for joining 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, well they actually have two types. There's one that they actually join two pieces together. I guess this one is just the one that is part-columbium and they have a shear strength of 50 KSI but they can be formed at room temperature and they're used for joining titanium and aluminum because 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 hole 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 two are the ones you concentrate the most on in the aircraft world. Now here's the cherry buck rivet, 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, 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 generic although all fast and some of the others would not want me to say that about it since they make competing rivets but a cherry rivet is a blind rivet with a locking collar and you have a pole-stam on it but it is a better structural rivet because they have better materials in it than say a pop rivet would have. They're also available in oversized diameters where 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 now how many thousands they are oversized but they will fit a reworked hole. They have shear strengths comparable to 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 Huck and Allfast is restricted by the guidelines. Here's an MS spec that tells you how you should use them and there's the statement also about the secondary structures versus primary. Here is a 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 stem 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 here 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 stem and the sleeve are different materials because the stem has to be strong to pull through and deform the sleeve the sleeve has to be ductile enough to form without cracking so you have so the strength of the rivet is a combination of those two materials so like here if you have the 50-55 aluminum with alloy steel Manel with stainless steel and here's Incanel 600 with an Incanel X750 pull stem on it and look at the, you can kick the temperature way up by going to the temperature resistant nickel stainless. Now Huck is also one of the big suppliers of rivets theirs are similar to cherry in fact if you look in Mill Handbook 5 for rivet allowables there are a lot of men there and I know in our fastener task group one of the things that 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 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 rivet so that it will cover Huck and cherry and all fast. Now move on to the next figure and we'll look at a standard Huck rivet see this is pretty much similar to the other one except in this case you're compressing the sleeve a little bit this way but 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 sheer so that it breaks off and you have the completed rivet installation. Now here is a Huck clinch 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 for many of the companies prior to this course. Now all fast make 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 regular cherry and Huck. So you see this one I guess it shows up better over here this is actually tapered so that it pulls through and keeps expanding it pulls through whereas the other one was a solid type but the final installation there is the same because you wind up with the thing pulled through to expand it and then you have the locking collar around the stem just in board 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 swaged collar that you put on it and this one the collar is sized 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 2024 T4 collar and you just pull the thing through, swage it on here the way that it swages on you can look around the top of it here and see whether it was formed properly so that it can be inspected from that side now this is not 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 would be installed in a drilled and reamed hole so it would give you a tighter tolerance on it now lock bolts are also commonly used and they are a non-expanding high strength fastener it has either a swaged collar or a threaded collar to lock them in place it's a variation of the high shear that I just showed you they're accepted in this case you normally have a stamp 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 a metallurgical balancing act you want the collar to form but on the other hand it can't crack so it can't be nearly as strong as the shanks so what you have is a fastener which is very strong in 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 installed and on the next page is one type of lock bolt this is a joe bolt and what you have here the locking sleeve or collar is expanded to form a shop head because you're rotating the stamp in a gun and holding the hex head in place so you're running this through as threaded here to expand the sleeve to form a head then the stamp is not so that when you reach the proper torque it breaks off now the hook bolt is a one with serrations on the shank rather than threads and it's swaged 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 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 that 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 a hook bolt installed and you see what they have is a notched stem you pull the thing in place there's your unsurrated shank that you put in the joint and then it breaks off once the collar is swaged in place now Hashere makes a high lock which is a similar one and it has to be fed through a hole from the far side and held with a key to prevent rotation while the nut 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, H11 tool steel, stainless steel and titanium now one of the things I wanted to call your attention here though the H11 tool steel which has been used in the past by SPS for a lot of their super high strength bolts 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 156 KSI shear that is 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 that you're not going to have some problems now here is a high lock the installation now this is threaded on so the threaded diameter is a little bit smaller here so that you can slide it through from the back side 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 torquing with breaks off when you reach the proper torque now here is an unusual one the high TIG is a high lock which is actually driven into an interference fit hole before the collar is installed and of course because you have the threads are slightly smaller you can do this then of course the interference bit increases the TIG 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 bit in a drilled and reamed hole now the tapered shank that's only a one don't ask me how this becomes a critical thing it's a 1.19 degree taper that it has on the sides and you lubricate the shank so you don't have to do anything to the hole you just drive the thing in but this interference bit keeps it from rotating while the lock nut with a captive washer attached to it is installed and there is a picture of one of them in the next figure so you have this is kind of showing this way although in reality it isn't 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 nut on it and you can, since it's driven in place the friction will hold it while you're installing the nut 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 them on the 777s, the 747s and so on and it's kind of an oddball in my opinion it has a deformed threads such that you use a kind of a socket type head that deforms to the point that it starts slipping and then you know that it is installed properly so be easier just to go with the picture on the next page I guess I better work with this one this one has a fluted threads on the stem here you can see it 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 dug-on thing until the nut deforms 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 the proper installation which is kind of strange but they work then they have another type that has a swage collar like the 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 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 materials fiberglass reinforced plastics this type of thing 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 130 degree head on it because you don't want the countersink very much on them because you want to avoid the grinding on the surfaces as much as possible because of the reinforcing fibers 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 a tight bit but not an interference bit 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 notch on the serrations to give you better holding power because now with this flatter angle here 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 a thing and here is one of them installed now notice how odd this head looks because it's 130 degrees instead of 82 or 100 most of the aerospace stuff is 100 degree counter sunk head and then see the it's a install very similar to the rest of the lock bolts and stuff like that it's a collar that is pushed in here you have a pole stem that breaks off when you've reached the proper load on them I believe monogram fasteners is the outfit that makes that one out of well they're 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 is stress corrosion sensitive a threaded lock bolt that's one of the ones that has the nut on it that 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 and the joint material and of course you can find lots of information on joints and rivet allowables which were determined by Tess in Milhambock 5 I think it's chapter 9 and Milhambock 5 has 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 and shear they even show the knife edge cutoffs remember I talked about the knife edge it's necessary to avoid they show where you cut it off to make sure you don't get knife edges and all that type of thing rivet installations are covered by Mill Standard 403 some corrosion prevention methods are covered by these two mill specs design and selection requirements for blind structural rivets and the MS33-522 and testing of fasteners is covered in Mill Standard 1312 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-some sections or something like that then this NAS 523 gives rivet codes and call outs that's the one that covers I believe the little X with the different designations on it for how to call out a specific rivet on a drawing whether it's counter something near side far side and all that business and then one of the other important things review the faster manufacturers design criteria before incorporating his fasteners into your design and that's one of the things that Dave Petraca 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 them on your design 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 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 Bernal test for aluminum usually and Rockwell for steel and the 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, a rock see a grade 8 fastener is about a Rockwell C33 I believe at least it gives you some indications and that's an easy test to run because you have a little machine you just slap the thing in there and run the test or at least a beginning test on it the Bernal is used for testing your aluminum stuff usually although Bernal 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 carbon steels are rated on the B scale and then when you get up I think a B100 is equivalent to around a C 18 or 20 or something like that for the harder materials let's go to the next figure here's a Bernal hardness tester and what you have is a little table that you put your sample on the ball is in the head here and you actuate the thing this is an older one I think when you just use a handle to actuate it nowadays they probably on these they probably make them that they are electronically actuated that one is for the aluminum this is one of the newer Rockwell models that got out of one of their catalogs or Wilson catalog same thing you have a a head here to put your sample on or platform and then you have the ball is in this part of it you program the thing to give you a given amount of load and it measures the indentation and gives you a reading that you can use with the table to check it out this mill standard 1312-6 gives a standard test method and specifies the apparatus to be used for hardness testing and all types of structural fasteners now the B scale this is the size diameter ball and the load that you use with it and the C has its own diameter and the load in 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 them into the shop the 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 co-worked the fastener and forming it if you take a reading on the outside some place it may not necessarily be the proper strength so to get accurate readings you need to get core hardness so you can take a machine it down get two flat parallel surfaces and use one of them for hardness testing and the other thing you can do if you have small fasteners that you can't do that with then you can mount them and 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 beauty of that is since you can't get through hardening in a fastener in 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 so on the little ones this is a zero to number five so that's 60 thousandths to an eighth diameter and 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 co-worked too much that you can get a ballpark type reading if the thing is big enough but this is not a very accurate reading it's only if you're wanting something just a general type reading now tensile testing this is something of course you can do and they do a little bit of that around here Carl Burkequist 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 lot 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, ultimate strength any elongation 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 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 hardenability of steel and boron is cheap and you don't need very much of it to add so you can take a 1020 steel and add a little boron to it and heat treat it so one of the tests that is used on acceptance of alloy steel fasteners is a carbon content test and there's a series of doing it one of the company that I believe makes the equipment that we have around here is called leco and what you have is some type of a furnace in which it's even either an induction or high frequency type or 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 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 in a little bit more detail here for a couple minutes yet it's high temperature combustion and you have two types of furnaces of high 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 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 you get carbon dioxide and sulfur dioxide and so with this furnace 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 discant such as Harold even put in there what to use magnesium perchlorate Harold Casper helped me on coming up with all of this stuff the samples here's one of the important things 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 weight in it and since it's such a small amount the weight of the sample has to be accurate the limitations on it also the specimen 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 if you get an erroneous reading it would show that it had a higher carbon content than it really had throughout graphite bearing specimens you have trouble with in other words you can't have graphite on the outside for a lubricant and of course the method is destructive so getting a sample and weighing it is a fairly short thing the high frequency furnace that they use has a a coil a heating coil on it and you have 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