 All right, continuing with inserts here are some other types, the unthreaded external diameter. Now a lot of these you'll buy something made out of plastic that has either this type or this type in it where you drill a hole and then ultrasonically force the insert in or you mold it in place. And then if you go to hang a picture or put up a shelf or something you use these type and drywall, the little old plastic expandable type which will hold a little bit but not a lot. So that's the more of the industrial type inserts. Now here's another one that's made by a company called PEM and it is a kind of a combination between an insert and a nut. It locks in place on the backside of the sheet and bites into the edges of the hole. Now these are usually used for the thin sheet where there is enough depth to put in an insert but they're not usually used for structural applications, critical things due to their unpredictable clenching capabilities because you don't know how it's going to clench into the surface, how much damage you'll do and stuff like that. Now nut plates, nut plates are sometimes called anchor nuts also. They're used actually as a blind nut. Blind nut is of course used in an inaccessible area, that's why it's called blind. You can't get to it. They can be fixed or floating and they can have most of the locking and sealing features of a regular nut but a floating nut plate does not provide angular misalignment fasteners. We had a case here one time that some people made that mistake. Floating nut plates only float parallel to the surface that they're mounted on so you can't tilt them sideways to make up for misalignment. They're also used on a sheet that's too thin to tap so the aerospace companies use them more than anybody else because you have to drill three holes to install one so that's a lot of labor and normally here are some samples of the fixed tape which is just a solid one and you drill the three holes, one for the bolt to go through into the threaded part of it, of the nut plate then you have two rivet holes for installing it so that it won't rotate and stays in place from now on while you thread into it. That's the two lug tape here. Here's what we always call the Mickey Mouse or corner plate, you can use those and take corners. Here's the one lug tape that the two rivets are back here and here's the sealed tape where you want to seal the thing, say if it's going to be on an airplane in a place where water would come in when you were moisture or something and you wanted to seal it all together you can get them that have the sealing capability. Now the floating tape is really the plate has slots in it if you will or bent up tabs here so that the threaded portion of it can slide back and forth but as I mentioned before it can only oscillate back and forth this way inside so it won't tilt to take up any angular misalignment. The Mickey Mouse is the same way in the one lug and the sealed and here's one that has a replaceable nut and this is used due to the fact that if you screw up the threads on one then without drilling out the rivets and replacing the nut plate you can take this thing out and slip another one back in place so those are kind of popular in some installations. Now going into the subject of threads and that is a big subject. The geometric information on threads you can find more specs and you know what to do with an ANT-C, NIS, Federal Standard Handbook H28 and so on so I could have put 100 pages of thread tables in here so I didn't bother to put any of those in. So you get into what is common and the most common inch threads are the UNC and UNF Unified National Course and Unified National Fine and then some of the others use with the UNEF extra fine, UNJCJF and UNR and UNK and those are maybe not the last two are not familiar with you but they are still used and in existence and then you can have cut or ground threads where you are making a one of a kind type situation. Now metric fasteners are available in Course, Fine and J-Threads. They are covered by ANT-C and H28 specifications but the aerospace ones as I mentioned earlier are covered by the NA and MA specs to cover the materials and geometry, plating and everything like that to make sure that you get what you want when you order them. Now as far as thread definitions go we talk about pitch diameter which is the center to center distance between or pitch I'm sorry is the distance between threads and of course for the English inch system we call it threads per inch and the metric system it is the actual distance between threads and we have major diameter which is the largest diameter of the threads and the minor diameter which is root diameter and a vanish cone and so on and I will have shortly here we'll have a table that I can point all these out here is the crest at the top of the thread flank is the flat portion pitch diameters the theoretical diameter where the shear thickness of mating threads is equal and now if we go on to the table maybe I can point these out. The pitch distance between threads is here and here is one and I want to point out while I'm here because Betsy had so much trouble getting the scanner to get this one in this is the thread lead angle here beta here is the vanish cone area here where you have incomplete threads and the pitch diameter is this heavy line here right there and then you have the OD here and then the flank of the thread is here and the crest is at the top of it and there's all sorts of things on there that you probably don't even care to know about one of the things that's a little confusing on this and I want to point out is that right here is the end of the threaded fastener that is going into the internal thread this part being internally threaded just in case it doesn't show up on your copying. Now on the thread pitch and lead of course I mentioned about the in the inch system is threads per inch like a quarter of 20 is quarter inch diameter with 20 threads per inch and in the the metric system you might have a say amma 8 by 1 or something like that means there's 1 millimeter distance between threads and then the here's something the lead of a screw thread is the distance that the nut will move forward on the screw per one 360 degree rotation and we hassled this one a lot when we did our drafting room manual and for a single lead thread which most of us were familiar with with fasteners the pitch and lead are the same but now when you want to go to a double lead it'll move forward two threads per 360 degree turns and so the best way to visualize this is the thread on a milk jug or bleach bottle or something like that where one revolution puts the lead all the way on that's probably triple lead because the thread has more angle to it. Now for rolled external threads the R in the UNRC or UNRF indicates rolled threads and actually this is not this terminology is not used that much because up to about three-quarter inch diameter threads are rolled cold rolled by the fastener manufacturers and then when you get the larger diameters you got to have some preheating in order to roll threads and you also have as I mentioned earlier way back you have to make sure that your bolt stock is annealed prior to starting to have it as soft as possible because you get cold work on the material during forming and of course the harder it gets the form so you want to start out with it as soft as possible and here is an important point to remember the heat treating of commercial fasteners is usually done after all the forming operations are completed but then when you get into the high strength stuff it is heat treated before the threads are put on their cold rolled in order to increase the fatigue resistance and actually make the threads stronger because you put residual stresses in the thread surfaces during the cold working cold rolling. Now on UNC threads of course that's the most common general purpose type thread a little deeper than fine threads because you have a since the coarser threads in the 60 degree angle between threads is the same so you go a little bit deeper so the minor diameters a little bit smaller but makes them a little bit easier to assemble without cross threading and of course all just about all small fasteners are coarse thread because it's kind of hard to make a 80 threads per inch or something like that on a fastener so anything usually up through a number 8 which is the 164 diameter is coarse thread even in aerospace then the UNC threads the easier to remove when they're corroded without stripping the threads there's different schools of thought on that as to how much easier it is if any and so on and their sloppier fit usually although you can get them in the tighter fits and I'll be covering the classes of fit later on now and they find threads UNF that's kind of the standard in the aerospace industry and nearly all fasteners with strengths above 150 ksi are UNRF or JF they have a slightly larger minor diameter than the coarse thread it gives you a little bit larger net cross sectional area and the smaller lead angle since you have more threads per inch they have a flatter angle so it makes it a little bit easier to adjust them the extra fine threads are used for tapped holes in thin or hard materials and holes with short edge distance they're also used on where you have adjusting screws burnier screws for adjusting things are usually extra fine threads but they're not used a lot in the ordinary structural fasteners the UNR and UNK thread comparison now this is kind of a little bit of an odd ball thing UNR threads are the same or the same ass UN threads most of the time because they're all rolled except that the root radius must be rounded but however people can say they've rounded the root radius but they didn't because there's no requirement for measuring it so somebody says yep I rounded the radius on these fasteners they may or may not have and there is no internal UNR thread now UNK threads which is a I'll have to admit tonight kind of an odd ball and are the same as UNR threads except that the root radius is measured in tolerance but we haven't bought any of them around here I don't think lately have we run okay I didn't remember I didn't remember buying them now constant pitch threads are used a lot in larger diameters and use a tailor a design to a particular need for example when you get up into fasteners larger than an inch diameter they usually will go to constant pitch because the regular threads are hard to farm they get too big in fact in case you ever get anything farmed any of you designers the limit I understand it is four threads per inch is as big a thread as you can get anywhere and I've never seen one called out I've seen them down to six I believe threads per inch so usually what you do is go to constant pitches of 8 12 or 16 threads per inch that way you can roll the threads even at elevated temperatures and it makes it a lot easier to adjust the torque tension because you don't have to turn as hard to get the thing to move for instance wheel pullers bearing pullers normally have real fine threads on them to give you that adjustment so that you can turn them without using a three foot braking bar left hand threads they do exist in fact Chrysler used to put them on their cars for some reason or other and people were always turning the wrench the wrong way because they try to tighten them be tightening the threads instead of loosening them when they got a flat because they didn't see that somewhere on the lug it was had an L stamped on it meaning it was left hand so there's not very many of them used they gas grills are one of the places the gas grill tanks they use them and on turnbuckles right ends and where do you have left hand nuts usually they put some sort of a marking on them that they're not big enough to stamp LH on them they will put notches on them or something to flag them do indicate that you do have left hand so just to make you aware of the fact that left handed stuff does exist now J threads the J thread is made in both external and internal forms although the internal form is a little bit dubious and they have a much larger root radius than the UNF or UNC threads and inspection of this radius is mandatory if you catch them since the root radius is larger the minor the minor diameter minimum diameter is larger giving a higher net cross sectional area and it also reduces the stress concentration factor in the threaded area so normally threads above 180 ksi will be J threads and some nuts have J threads that are rolled on them but there are no J taps for internal holes now the UNJC threads or coarse threads with the same characteristics as the UNJFs however they're not that common except in the small sizes up through a number eight now a J bolt requires a J nut but a J nut will fit a regular bolt of the same size thread because the radius is not that critically controlled on the nut even though they say it is and if you can go into the ANSI B 1.1 specs and all that get all the information on the thread geometry everything more than you care to know now a tapped hole has cut threads because that's the only way you can get it formed is to cut it so regardless of the type of thread informed that you're talking about internal threads internal threads are cut with some sort of a tap although you can you can roll some on on the nuts they do have capabilities for rolling them but the tapped holes are harder to inspect than an external thread external so their design margin should be higher to allow for that because really if you want to check an internal thread and you want to measure the root radius or something like that about the only way to do it is use a there's a dental plaster that you can put in there that is soft enough like for instance if you get any you probably get the impression at some time for a bridge or something like that for your for your mouth they use a soft type of plaster that will maintain the configuration but you can strip it out well they use stuff like that to check internal threads where they need to check them so but that's a lot of trouble to take the mix of stuff up get yourself a cast of it and then use an optical comparator to measure it so it's usually not done and there is no J thread for tapped holes to say mentioned there earlier now thread classes or fits this is a the the number associated with these is associated with a tolerance band so the the one the class one type thread would be the the nut and bolt you buy from the hardware store and you put the nut on the bolt and you can jiggle it back and forth because it's a sloppy a fit that would be a class one class three class two is industrial grade class three is the aerospace grade where the thing fits quite snug and the aerospace industry uses primarily the class three threads now you can go into h-28 federal standard h-28 or that's a handbook or antsy specs and so on and you can find out what the tolerance levels are for each one of these threads for a given class if you're so inclined cut or ground threads are they're normally made on a one-of-a-kind fastener for a specific application so but remember that tapped holes are cut so that you can't cold form threads very well in a tapped hole so cut threads are weaker than rolled threads and thread cutting destroys the grain flow in the piece of material now this is one of the reasons why your super strength bolts have forged heads because you have to maintain the proper grain flow in the head to shank area in order to cut down on stress concentration now for metric threads once again to refresh your memory on them they're usually described as a m and then the diameter like a m8 times the pitch whatever it is and the example I've given there is that one I believe is a that's fine thread or a eight millimeter diameter and the the pitch value tells whether the thread is coarser fine but it there's no designation like an mc or an mf to indicate whether it's fine or coarse so so if you're unfamiliar with metric threads about the only way to tell is go look it up in a table to see whether you have fine or coarse threads the only further identifier on the metric is a j where you have j threads so and remember also that the property class of the material has to be specified to tie down the strength requirements so so just don't call out an m8 by one and say that's the end of it you gotta also give a property class to tie down the strength now metric thread classes they have two diameter tolerances which is kind of seemed odd to me but nevertheless that's the way to do it first one is for pitch diameter and the second one is for crest diameter which is the major diameter for external thread and the minor diameter for internal threads now if you only give one value there is applying the same tolerances to both crest and pitch if they give two values you have then two two different tolerance levels for the two of them now their numbers go from three to nine on on the tolerance levels with four to six being the normal range for the tolerances and they give latter number of values for the pitch and crest diameters where they have different tolerances now I think just the next no I'm sorry it'll be the one after this on the you have sample callouts given in the antsy y14.6 and on our next table which you can go ahead and go to Alice we have the we have some sample callouts here this would be a way of calling these out and you can read them in your handout I'm not sure whether you can read them anywhere else but now notice on the pitch diameter here you have a 4h and on the major diameter you have a 6h so you have two different levels of tolerance on them now if you come down to the other one down here in the below where you have the internal thread you have a 4h and 5h for your pitch and diameter tolerance so with the metric it is you have to really pay attention to what what you're calling out because to me it's more confusing and then of course on that slide there was also a single number given there of six I believe somewhere along the line no it's the next one that has a has a six on it where you have the same tolerances on both the pitch and minor diameter so this next one it gives you also a way of calling it out and an explanation here on the left on the external internal and so on and one of the things they have added there which we will be covering later on are the methods of inspection the system 21 and 22 and 23 gauging systems when we go into inspection and acceptance of fasteners we'll cover those moving on here is a comparison and to me this is a nice thing to have because it kind of gives you a yardstick to measure from on the comparison of inch to metric on the thread tolerances now somebody asked me the other day about what would be a class one in metric see I don't have a one on there I just have the two two and three and I think it's a E classification in the tolerances because metric usually does not come with that classification it's normally either the the the six is usually about what they they call out for it and so I think it's a E but anyway if you go into the antsy specs they give the tolerance bands in there and I think that that is the one if IFI puts out a manual or a book on metric fasteners that has all of the different antsy stuff in there so anyway that that is something you can refer back to now here's for thread relief I put this in here because it's something it is quite common to have a thread relief particularly on what the shoulder bolt that we'll be covering next but this diameter on the thread relief should not be larger than the minor diameter of the threads or you get in trouble when you try to thread it and the sometimes in a tapped hole you even put in internal thread relief where you don't want to kind of run your tap in there and have incomplete threads and all sorts of notches and gouges and everything like that so you have thread relief where you when you tap through at least it will come out clean since thread relief was a part of a shoulder bolt designation I went ahead and put in the shoulder bolt here now they can be used as an actuator pin when you're tightening the shoulder up against the surface to tighten it up and then using this big shank for an actuator pin there use some in disc brakes installation on cars on some of me use a shoulder bolt to take them down because you want to have a loose bit on the shank and a tight fit so they lock tight them in with this threaded area here the only thing is a shoulder bolt is real bad if you have put it in single shearer because this reduced cross section here has a high stress concentration on it if you go into bending so it will bend very easily there so you got to be careful to make sure the top part of it near the head is supported when you're using it now for tapped threads I don't know probably a lot of you uh shade tree mechanics have done thread tapping and uh you got to do it carefully to get the proper thread with the correct alignment and this means you got to usually tell you if you're doing it yourself what size drill to use drill the hole with and then the problem is to start that tap by hand and get it to go in properly as you don't wind up with something lopsided well of course on machines you can get away from that but sometimes on critical applications they actually have to drill a hole and then remit to get it to exactly the right diameter for tapping and of course the required length of a tapped hole is dependent on the hardness of the material and the tensile load developed by the install fastener and one of the key things here that you got to think of too is the length should be based on complete threads because when you start out you don't have complete threads and you don't wind up with complete threads at the bottom so we have a an example here of the different types of taps here you start out the drill in a hole with a tap drill then you use a tapered tap which has a whole bunch of incomplete threads on in fact seven to ten of them are incomplete this gives you something that you can start better then you have a plugged tap here which has an intermediate one that has fewer incomplete threads and then if you have to make the uh whole tapped all the way down then you use a bottom tap or a flat bottom tap here to tap it down to where you only have about one incomplete thread now my my brother is a retired mill rate and he said that when they got them at the steel mill they usually got them in sets of three like that so that you could start out with your tapered one to start the hole and then go to the other two to finish it up so that you'd wind up with a decent tapped hole so we will pause here and resume on threads after the break