WEBVTT 00:00:00.396 --> 00:00:05.116 A:middle >> This is a lecture on working drawings, which consist 00:00:05.116 --> 00:00:06.266 A:middle of a complete set 00:00:06.266 --> 00:00:09.446 A:middle of standardized drawings specifying the manufacture 00:00:09.446 --> 00:00:12.466 A:middle and assembly of a product based on its design. 00:00:12.466 --> 00:00:14.536 A:middle So we're going to be putting everything that we've talked 00:00:14.536 --> 00:00:17.186 A:middle about so far in terms of grading parts, 00:00:17.566 --> 00:00:21.696 A:middle into this complete set called "Working Drawings." 00:00:21.926 --> 00:00:24.966 A:middle The set should completely describe the parts, 00:00:25.086 --> 00:00:26.936 A:middle both visually and dimensionally -- 00:00:27.586 --> 00:00:30.146 A:middle always think about whoever is going to manufacture 00:00:30.146 --> 00:00:33.526 A:middle or implement your design; should show think the parts 00:00:33.526 --> 00:00:36.296 A:middle and the assembly, how the different parts fit together; 00:00:36.876 --> 00:00:39.026 A:middle and identify all the parts needed, 00:00:40.166 --> 00:00:43.136 A:middle as well as standard parts. 00:00:43.376 --> 00:00:47.716 A:middle Standard parts are parts that you did not design or parts 00:00:47.716 --> 00:00:49.836 A:middle that are commonly available in stores, 00:00:50.156 --> 00:00:52.066 A:middle as opposed to nonstandard parts. 00:00:52.296 --> 00:00:53.656 A:middle The main parts of the complete set 00:00:53.656 --> 00:00:56.166 A:middle of working drawings include detail drawings 00:00:56.166 --> 00:00:57.556 A:middle of each nonstandard part. 00:00:57.556 --> 00:01:02.376 A:middle So any part of your design that is not going 00:01:02.376 --> 00:01:05.776 A:middle to be bought needs detail drawings. 00:01:05.776 --> 00:01:09.416 A:middle You also need an assembly or some assembly drawing, 00:01:09.416 --> 00:01:11.766 A:middle showing all the standard and nonstandard parts 00:01:11.766 --> 00:01:14.096 A:middle in a single drawing, how they fit together, 00:01:15.076 --> 00:01:18.726 A:middle and a bill of materials, as well 00:01:18.726 --> 00:01:22.316 A:middle as a title block describing information needed 00:01:22.316 --> 00:01:23.736 A:middle for a drawing. 00:01:24.286 --> 00:01:26.986 A:middle Going in detail to the detail drawing, 00:01:27.056 --> 00:01:30.576 A:middle it's a dimension multi-view drawing of a single part, 00:01:30.876 --> 00:01:33.546 A:middle describing the part's shape, size, material, 00:01:33.546 --> 00:01:36.236 A:middle and finish in sufficient detail for the part 00:01:36.236 --> 00:01:38.696 A:middle to be manufactured based on the drawing alone. 00:01:39.456 --> 00:01:42.936 A:middle So this is where you're going to first create a 3D model, 00:01:42.976 --> 00:01:47.936 A:middle and then turn it into multi-views, and add dimensions 00:01:48.016 --> 00:01:50.826 A:middle and any additional descriptions needed in order 00:01:50.826 --> 00:01:52.486 A:middle to manufacture the part. 00:01:52.686 --> 00:01:56.126 A:middle So it should show all the necessary dimension views, 00:01:57.116 --> 00:01:59.276 A:middle indicate the materials and tolerances, 00:01:59.706 --> 00:02:02.386 A:middle indicate any finish treatments, plating, et cetera, 00:02:02.986 --> 00:02:06.266 A:middle and requirements for surface finish roughness. 00:02:06.436 --> 00:02:09.686 A:middle Standard parts are not included in detail drawings 00:02:09.766 --> 00:02:12.656 A:middle because they are parts that are normally purchased 00:02:12.656 --> 00:02:13.696 A:middle and not manufactured. 00:02:14.176 --> 00:02:17.926 A:middle It is often preferred to show just one part per sheet in order 00:02:17.926 --> 00:02:19.666 A:middle to be less confusing, 00:02:19.746 --> 00:02:21.946 A:middle unless it's a really fairly simple part, 00:02:22.136 --> 00:02:25.226 A:middle or a group of simple parts you can have them more 00:02:25.226 --> 00:02:27.296 A:middle than one in one sheet. 00:02:27.296 --> 00:02:29.246 A:middle When more than one detail is placed on a sheet, 00:02:29.276 --> 00:02:32.226 A:middle the spacing between details is carefully planned 00:02:32.756 --> 00:02:36.696 A:middle so that it's really clear which parts of the drawing are 00:02:36.946 --> 00:02:38.916 A:middle for which part of the model. 00:02:40.416 --> 00:02:43.026 A:middle An assembly drawing shows how each part 00:02:43.026 --> 00:02:45.426 A:middle of a design is put together, both -- 00:02:45.576 --> 00:02:48.116 A:middle you need to show both the standard and nonstandard parts. 00:02:48.496 --> 00:02:52.096 A:middle If the design depicted is only part of a total assembly, 00:02:52.336 --> 00:02:54.886 A:middle it is referred to as "subassembly." 00:02:54.956 --> 00:02:57.586 A:middle If your entire assembly is complicated, you might want 00:02:57.646 --> 00:03:00.036 A:middle to divide it into subassemblies. 00:03:00.786 --> 00:03:03.076 A:middle You usually do not include dimensions 00:03:03.596 --> 00:03:05.356 A:middle in the assembly drawing, 00:03:05.646 --> 00:03:08.716 A:middle unless those dimensions are critical during assembly. 00:03:09.596 --> 00:03:11.066 A:middle Hidden lines are usually needed. 00:03:11.736 --> 00:03:13.586 A:middle The main purpose of the assembly drawing is 00:03:13.586 --> 00:03:16.686 A:middle to really show only how the different parts fit together. 00:03:17.076 --> 00:03:18.726 A:middle And there are different types of assemblies, 00:03:18.726 --> 00:03:20.106 A:middle depending on your needs. 00:03:20.616 --> 00:03:24.096 A:middle An outline assembly gives a general graphic description the 00:03:24.096 --> 00:03:24.906 A:middle exterior shape. 00:03:24.906 --> 00:03:27.766 A:middle And this is usually used for simple assemblies. 00:03:28.516 --> 00:03:29.956 A:middle We have sectioned assemblies 00:03:30.056 --> 00:03:33.326 A:middle that give general graphic description 00:03:33.326 --> 00:03:36.136 A:middle of the interior shape by passing a cutting plane 00:03:36.656 --> 00:03:37.486 A:middle through all the parts. 00:03:37.486 --> 00:03:40.356 A:middle So if you have complicated assemblies that have a lot 00:03:40.356 --> 00:03:43.306 A:middle of interior parts, sectioned assembly might be useful 00:03:43.306 --> 00:03:46.206 A:middle to show how these interior parts fit together. 00:03:46.546 --> 00:03:49.766 A:middle A pictorial assembly gives a general graphic description 00:03:49.766 --> 00:03:52.206 A:middle of each part, standard and nonstandard, 00:03:52.206 --> 00:03:55.686 A:middle and uses center lines to show how the parts are assembled. 00:03:56.236 --> 00:04:00.066 A:middle For our lab, you're going to use this pictorial assembly. 00:04:00.746 --> 00:04:03.066 A:middle Now, here's an example of a pictorial assembly, 00:04:03.286 --> 00:04:05.386 A:middle and it shows the different parts. 00:04:05.676 --> 00:04:08.736 A:middle Center lines here indicate how the different parts fit 00:04:08.826 --> 00:04:10.286 A:middle connected [phonetic] to each other. 00:04:10.796 --> 00:04:14.176 A:middle And here's an assembled drawing of the parts. 00:04:14.856 --> 00:04:17.196 A:middle Here's an example of a sectioned assembly, 00:04:18.226 --> 00:04:20.426 A:middle showing different hatch patterns 00:04:20.426 --> 00:04:23.186 A:middle for different parts in the assembly. 00:04:24.136 --> 00:04:26.056 A:middle The material for the part can be identified 00:04:26.056 --> 00:04:28.826 A:middle by different hatch patterns, of course according 00:04:28.826 --> 00:04:32.086 A:middle to the standard symbols for the hatch patterns. 00:04:32.366 --> 00:04:36.746 A:middle Or you can also use different angles for the different parts 00:04:36.746 --> 00:04:39.036 A:middle of the assembly to distinguish them. 00:04:39.156 --> 00:04:42.926 A:middle Now, for very thin parts, such as this indicated here, 00:04:43.406 --> 00:04:47.616 A:middle instead of using section lines, you can just fill it 00:04:47.616 --> 00:04:52.236 A:middle in in black; parts like gaskets shown above too small to hatch 00:04:53.306 --> 00:04:55.836 A:middle and are filled in solid black. 00:04:56.556 --> 00:05:00.116 A:middle The parts list, also known as the bill of materials, 00:05:00.386 --> 00:05:05.096 A:middle includes for each part a part name, item number, material, 00:05:05.096 --> 00:05:07.076 A:middle and the quantity that's for the assembly. 00:05:07.966 --> 00:05:11.486 A:middle For standard parts, include a catalog number and the company 00:05:11.636 --> 00:05:14.426 A:middle or a store where you can buy them. 00:05:14.756 --> 00:05:17.456 A:middle Parts lists may be on a separate document, 00:05:17.456 --> 00:05:20.556 A:middle especially if you have a fairly complicated assembly. 00:05:21.246 --> 00:05:24.406 A:middle You can identify each part on the drawing 00:05:24.406 --> 00:05:25.556 A:middle by using leader lines 00:05:25.556 --> 00:05:28.566 A:middle and balloons assigning each part a detail number 00:05:29.036 --> 00:05:32.096 A:middle in sequential order and keyed to the list 00:05:32.226 --> 00:05:34.246 A:middle of parts in the parts list. 00:05:35.316 --> 00:05:38.946 A:middle Or if there's space you can place the part number directly 00:05:38.946 --> 00:05:40.656 A:middle on the drawings face. 00:05:40.656 --> 00:05:44.236 A:middle An example of the parts list of bill of materials, 00:05:44.486 --> 00:05:49.736 A:middle it lists chronologically each item and the number you need 00:05:49.736 --> 00:05:53.806 A:middle for each name and description as well. 00:05:53.806 --> 00:05:57.916 A:middle And here's the leaders with numbers 00:05:57.916 --> 00:06:00.196 A:middle and balloons corresponding to each 00:06:00.196 --> 00:06:01.906 A:middle of the parts in the parts list. 00:06:02.526 --> 00:06:05.276 A:middle The title blocks, we've talked about it previously. 00:06:05.636 --> 00:06:08.646 A:middle It's used to record all the important information necessary 00:06:08.646 --> 00:06:09.636 A:middle for the working drawings. 00:06:09.696 --> 00:06:11.306 A:middle The title block is normally located 00:06:11.676 --> 00:06:13.076 A:middle in the lower right-hand corner. 00:06:13.456 --> 00:06:15.826 A:middle Almost all engineering firms have their standard 00:06:15.916 --> 00:06:17.936 A:middle or default elements that are included 00:06:17.936 --> 00:06:19.676 A:middle in the engineering drawings. 00:06:19.736 --> 00:06:24.146 A:middle But some of the information should include name, 00:06:24.146 --> 00:06:26.606 A:middle and address of the company, or design activity, 00:06:26.666 --> 00:06:29.386 A:middle title of a drawing, drawing number, names and dates 00:06:29.386 --> 00:06:32.216 A:middle of drafters, et cetera, predominant drawing scale, 00:06:32.566 --> 00:06:35.476 A:middle a drawing sheet size letter designation, 00:06:36.246 --> 00:06:39.666 A:middle actual or estimated weight of the item, sheet number 00:06:39.746 --> 00:06:41.676 A:middle if there are multiple sheets. 00:06:42.656 --> 00:06:45.406 A:middle With respect to scales there are different ways of calling 00:06:45.406 --> 00:06:48.866 A:middle out scales that's typical for mechanical engineering, 00:06:49.296 --> 00:06:50.316 A:middle and most other engineering. 00:06:50.376 --> 00:06:52.856 A:middle The scale is in the form one is to something. 00:06:53.876 --> 00:06:57.196 A:middle So length of the drawing, one, corresponded 00:06:57.236 --> 00:06:59.726 A:middle to the length in real world. 00:07:00.046 --> 00:07:03.926 A:middle So for instance, if you get a map and the map says a scale 00:07:03.926 --> 00:07:08.656 A:middle of one -- one is to 2,000, a length of 20 millimeters 00:07:08.816 --> 00:07:13.296 A:middle on the map corresponds to 20 millimeters times 2,000 is equal 00:07:13.296 --> 00:07:16.796 A:middle to 40 kilometers in the real world. 00:07:16.926 --> 00:07:18.956 A:middle Sometimes an architecture -- 00:07:19.916 --> 00:07:21.516 A:middle sometimes often civil engineering, 00:07:21.846 --> 00:07:25.176 A:middle instead of using one is to something, as the callout, 00:07:25.706 --> 00:07:29.276 A:middle here you give the size on the drawing 00:07:29.956 --> 00:07:32.386 A:middle that equals the size in the real world. 00:07:32.576 --> 00:07:37.306 A:middle An example is two inches equals five feet, meaning a distance 00:07:37.306 --> 00:07:41.136 A:middle of two inches in the drawing corresponds 00:07:41.196 --> 00:07:43.406 A:middle to five feet in real life. 00:07:43.606 --> 00:07:47.596 A:middle Now, we've talked about first and third angle projections. 00:07:47.596 --> 00:07:49.756 A:middle You have to be careful; in North America we use the third 00:07:49.756 --> 00:07:50.646 A:middle angle projections. 00:07:51.126 --> 00:07:54.806 A:middle And in Europe they used mostly first angle projections. 00:07:55.196 --> 00:07:58.146 A:middle And you need to specify this in your drawing, 00:07:58.146 --> 00:07:58.686 A:middle in the title block. 00:07:59.226 --> 00:08:01.836 A:middle Third angle projections are used in the US 00:08:01.836 --> 00:08:06.376 A:middle when the front view is below the top, and to the left 00:08:06.376 --> 00:08:07.096 A:middle of the right-side view. 00:08:07.096 --> 00:08:09.866 A:middle So the top is below the front, and the right is 00:08:09.996 --> 00:08:11.416 A:middle to the right of the front. 00:08:12.866 --> 00:08:14.716 A:middle The first angle projection is -- 00:08:15.526 --> 00:08:18.516 A:middle we are initially [phonetic] especially if you are used 00:08:18.516 --> 00:08:20.766 A:middle to third angle projection. 00:08:21.056 --> 00:08:23.626 A:middle Instead -- if you remember our glass box model, 00:08:24.086 --> 00:08:28.456 A:middle instead of projecting the features of an object, 00:08:28.456 --> 00:08:31.336 A:middle the frontal plane, to get the front view, 00:08:31.686 --> 00:08:34.176 A:middle in the first angle projection you actually project it 00:08:34.206 --> 00:08:34.696 A:middle to the back. 00:08:35.086 --> 00:08:38.316 A:middle So you project it to the shadow of an object behind it. 00:08:38.696 --> 00:08:43.746 A:middle So as a result the top is typically below the front view, 00:08:43.776 --> 00:08:46.066 A:middle and the right side view is to the left of the front view. 00:08:46.066 --> 00:08:48.286 A:middle As I said, this is confusing 00:08:48.396 --> 00:08:51.026 A:middle since we've been using third angle projection. 00:08:51.026 --> 00:08:52.486 A:middle But I just want you to be aware 00:08:53.036 --> 00:08:55.436 A:middle that other systems are also used. 00:08:55.596 --> 00:08:58.336 A:middle The projection used in the drawing should be indicated 00:08:58.336 --> 00:09:03.776 A:middle in the title block, so nothing should confuse the audience. 00:09:03.776 --> 00:09:08.206 A:middle And here's the symbol for the first angle projection. 00:09:08.656 --> 00:09:12.756 A:middle As I said, the front view is above the top view, 00:09:13.056 --> 00:09:15.776 A:middle and the right side view is to the left of the front. 00:09:16.056 --> 00:09:17.926 A:middle As I said, it looks weird. 00:09:18.046 --> 00:09:21.006 A:middle We always use this convention here. 00:09:21.446 --> 00:09:23.626 A:middle There's the symbol for the first angle project. 00:09:23.766 --> 00:09:27.726 A:middle And if you look at the symbol, it would look weird to you 00:09:28.026 --> 00:09:31.796 A:middle that the smaller circle is visible, 00:09:32.846 --> 00:09:36.466 A:middle because if you're looking from the right of this object here, 00:09:36.466 --> 00:09:40.046 A:middle it should be -- and this is a consequence 00:09:40.046 --> 00:09:41.286 A:middle of the first angle projection. 00:09:41.796 --> 00:09:44.216 A:middle The third angle projection is what we will be using, 00:09:44.216 --> 00:09:47.266 A:middle and this is the one that you should be really familiar with. 00:09:47.266 --> 00:09:50.096 A:middle The top view is above the front, and the right-side view is 00:09:50.146 --> 00:09:51.276 A:middle to the right of the front view. 00:09:51.276 --> 00:09:54.576 A:middle And this assemble here, the two circles here, 00:09:54.576 --> 00:09:56.166 A:middle the two concentric circles to the left 00:09:56.686 --> 00:10:00.426 A:middle for this trapezoid here, seems correct to us, 00:10:00.606 --> 00:10:03.606 A:middle because if you are looking at this trapezoid here, 00:10:03.646 --> 00:10:05.206 A:middle which is to be the object from the left, 00:10:05.686 --> 00:10:09.146 A:middle you should see the smaller circles visible 00:10:09.146 --> 00:10:10.436 A:middle because it's closer to you. 00:10:10.976 --> 00:10:13.936 A:middle As I said, for us this looks weird because according 00:10:13.936 --> 00:10:16.556 A:middle to our third angle projection, 00:10:17.386 --> 00:10:20.576 A:middle the smaller of the two circles should be in because 00:10:21.166 --> 00:10:24.816 A:middle from our third angle projection it's actually further away 00:10:24.816 --> 00:10:25.436 A:middle from us. 00:10:26.006 --> 00:10:28.786 A:middle And the first thing you need to do is, you know, 00:10:28.786 --> 00:10:33.786 A:middle if you're not sure is to check whether the drawing is using the 00:10:33.786 --> 00:10:36.046 A:middle first angle projection, you would see the symbol; 00:10:36.076 --> 00:10:38.606 A:middle or if third angle projection, you would see the symbol, 00:10:38.606 --> 00:10:41.416 A:middle the concentric circle to the left of that trapezoid. 00:10:42.716 --> 00:10:46.716 A:middle A little bit on threaded fasteners; because we talked 00:10:46.716 --> 00:10:50.226 A:middle about assemblies we need fasteners to connect 00:10:50.226 --> 00:10:52.256 A:middle or join parts together. 00:10:52.736 --> 00:10:55.356 A:middle Okay; so fastening is a method of connecting or joining two 00:10:55.356 --> 00:10:59.676 A:middle or more parts together using processes or devices. 00:11:00.306 --> 00:11:03.656 A:middle Threaded fasteners are cylindrical surfaces 00:11:03.656 --> 00:11:05.296 A:middle with mating helical cuts. 00:11:05.566 --> 00:11:08.156 A:middle And helical threads have three main applications, 00:11:08.556 --> 00:11:12.886 A:middle number one to hold the parts together; it can also be used 00:11:12.926 --> 00:11:16.246 A:middle to adjust the position of the parts connected to each other 00:11:16.936 --> 00:11:19.626 A:middle by rotating the helical threads; 00:11:20.366 --> 00:11:22.836 A:middle it can also be used to transmit power. 00:11:24.076 --> 00:11:28.936 A:middle Some terminology for threads, okay, the depth -- 00:11:29.206 --> 00:11:31.746 A:middle the highest part of the thread here, 00:11:31.746 --> 00:11:34.646 A:middle this is for an external thread, is called the crest, 00:11:34.646 --> 00:11:36.246 A:middle and the lowest part is the root. 00:11:37.076 --> 00:11:41.776 A:middle And the depth is the difference between the crest and the root. 00:11:41.936 --> 00:11:44.436 A:middle And this is of course the axis of the thread. 00:11:45.126 --> 00:11:47.146 A:middle This is the minor axis. 00:11:47.366 --> 00:11:53.846 A:middle Minor diameter is the diameter measured to the root, 00:11:54.026 --> 00:11:59.866 A:middle and the major diameter is measured to the crest. 00:12:00.766 --> 00:12:03.466 A:middle Now, the pitch is the distance 00:12:03.466 --> 00:12:08.066 A:middle between either two successive crests, or two successive roots. 00:12:09.776 --> 00:12:15.836 A:middle For an internal thread, here's the corresponding definitions. 00:12:15.886 --> 00:12:18.796 A:middle The crest is -- that's the lowest part, 00:12:19.046 --> 00:12:23.256 A:middle and the root is the highest part for an internal thread. 00:12:23.506 --> 00:12:26.256 A:middle There are many different forms 00:12:26.256 --> 00:12:28.826 A:middle of commonly used forms of threads. 00:12:29.106 --> 00:12:33.216 A:middle We have sharp V, American national, different types, 00:12:33.216 --> 00:12:36.756 A:middle depending on the profile of the threads that you use. 00:12:36.756 --> 00:12:37.816 A:middle We're going to talk a little bit 00:12:37.816 --> 00:12:46.706 A:middle about the unified USA thread series; and after 1948 00:12:46.856 --> 00:12:49.886 A:middle by US, Canada, and UK. 00:12:50.066 --> 00:12:52.446 A:middle To make sure -- these were designed in order 00:12:52.446 --> 00:12:54.176 A:middle to make the fasteners interchangeable. 00:12:55.206 --> 00:13:01.196 A:middle The UN designation specification has two main elements, the major 00:13:01.196 --> 00:13:02.706 A:middle or outside diameter of the thread, 00:13:03.696 --> 00:13:07.046 A:middle which is specified either by a size number running from zero 00:13:07.046 --> 00:13:10.236 A:middle to 12, corresponding to point zero six 00:13:10.596 --> 00:13:12.206 A:middle to point two one six inches. 00:13:13.736 --> 00:13:14.766 A:middle That's the type number. 00:13:14.766 --> 00:13:20.886 A:middle The major diameter can also be specified in fractions 00:13:20.886 --> 00:13:23.766 A:middle of inches, and then the inverse pitch, 00:13:25.226 --> 00:13:26.996 A:middle which is threads per inch. 00:13:26.996 --> 00:13:29.626 A:middle So instead of giving the distance between the crest, 00:13:29.626 --> 00:13:33.306 A:middle or the distance between the roots, you take one divided 00:13:33.306 --> 00:13:39.596 A:middle by the distance between the crest will give you the inverse 00:13:39.676 --> 00:13:43.706 A:middle pitch, which is the number of threads per inch. 00:13:46.426 --> 00:13:51.256 A:middle Here's the UN thread series, the Coarse series, or UNC, 00:13:51.846 --> 00:13:55.446 A:middle used for rapid assembly, generally used. 00:13:55.446 --> 00:14:01.226 A:middle They are a Coarse and are easy to engage and start using. 00:14:01.926 --> 00:14:03.186 A:middle We have the FINE series, UNF, 00:14:03.726 --> 00:14:05.716 A:middle for applications requiring greater strength, 00:14:06.416 --> 00:14:08.336 A:middle or where the length of engagement is limited; 00:14:08.686 --> 00:14:11.146 A:middle used extensively for aircraft 00:14:11.146 --> 00:14:16.936 A:middle and automobile manufacturing requiring more accuracy. 00:14:17.326 --> 00:14:20.486 A:middle Extra fine series for highly stressed parts, 00:14:20.866 --> 00:14:23.486 A:middle as parts that are supporting a lot of loads. 00:14:24.016 --> 00:14:26.496 A:middle We also have the 8N series, which is a substitute 00:14:26.496 --> 00:14:27.656 A:middle for the coarse thread series 00:14:27.656 --> 00:14:32.716 A:middle for larger diameters, larger than one inch. 00:14:33.276 --> 00:14:36.956 A:middle And all diameters have eight threads per inch, 00:14:37.476 --> 00:14:40.936 A:middle often used as bolts for high-pressure pipe applications. 00:14:41.766 --> 00:14:45.226 A:middle We have the number five, which is the 12N series. 00:14:45.626 --> 00:14:47.786 A:middle It's a continuation of the fine thread series 00:14:48.056 --> 00:14:49.696 A:middle for larger diameters. 00:14:49.696 --> 00:14:51.926 A:middle And the 16N series, continuation 00:14:51.926 --> 00:14:56.226 A:middle of the extra fine thread series for large diameters. 00:14:56.376 --> 00:15:02.796 A:middle There is an illustration of the callout. 00:15:03.796 --> 00:15:08.446 A:middle We have here the diameter, three-fourths, 00:15:09.946 --> 00:15:19.916 A:middle the threads per inch, NC, national, the coarse series, 00:15:20.146 --> 00:15:24.976 A:middle the class of 5th -- the 7 class of 5ths [phonetic], 00:15:24.976 --> 00:15:29.366 A:middle LH for left-handed, and thread depth. 00:15:31.796 --> 00:15:37.356 A:middle Some of the default values may not be part of the callout. 00:15:37.356 --> 00:15:41.186 A:middle So, for instance, it's needed to be implied, because it's based 00:15:41.186 --> 00:15:43.486 A:middle on the diameter and the threads per inch. 00:15:44.036 --> 00:15:46.336 A:middle The class default is 2A or 2B. 00:15:47.376 --> 00:15:51.676 A:middle And if there's no designation for the handedness, 00:15:51.746 --> 00:15:53.896 A:middle the default is right-handed. 00:15:55.976 --> 00:15:59.486 A:middle There are two types of classes, as mentioned earlier; 00:16:00.296 --> 00:16:04.496 A:middle refers to external threads and internal threads. 00:16:05.946 --> 00:16:09.096 A:middle Class descriptions provide liberal allowance for ease 00:16:09.326 --> 00:16:11.496 A:middle of assembly when threads are dirty 00:16:11.636 --> 00:16:13.466 A:middle or slightly damaged -- not commonly used. 00:16:13.466 --> 00:16:17.516 A:middle And we have class two for commercially produced bolts, 00:16:17.546 --> 00:16:22.016 A:middle screws, which are far more common; and class three used 00:16:22.016 --> 00:16:24.116 A:middle in precision assemblies. 00:16:25.186 --> 00:16:28.326 A:middle As opposed to the unified thread series, the UN, 00:16:28.326 --> 00:16:31.506 A:middle we also have the metric thread specifications. 00:16:32.486 --> 00:16:34.016 A:middle And the form is slightly different. 00:16:34.276 --> 00:16:36.676 A:middle And for metric here's the callout. 00:16:37.196 --> 00:16:40.796 A:middle And it gives you the major diameter of the thread, 00:16:41.466 --> 00:16:44.426 A:middle and here instead of giving the inverse pitch, 00:16:44.516 --> 00:16:47.626 A:middle it actually gives you the pitch which is the distance 00:16:47.626 --> 00:16:50.376 A:middle between either the crest or the root. 00:16:51.546 --> 00:16:54.216 A:middle So the pitch is stated explicitly 00:16:54.346 --> 00:16:55.966 A:middle in the metric specification, 00:16:56.076 --> 00:17:01.566 A:middle as opposed to the UN wherein you give the inverse pitch; 00:17:03.056 --> 00:17:06.506 A:middle so inverse pitch for the unified specification. 00:17:08.576 --> 00:17:12.936 A:middle There are different ways of specifying thread details 00:17:12.936 --> 00:17:15.446 A:middle in drawings, depending on your needs. 00:17:15.926 --> 00:17:17.926 A:middle We have the detailed thread representation. 00:17:19.316 --> 00:17:24.306 A:middle As you can see, the detail it shows the individual crest 00:17:26.096 --> 00:17:27.116 A:middle and root lines. 00:17:29.006 --> 00:17:33.656 A:middle It's used when the diameter of the thread is one inch or larger 00:17:33.906 --> 00:17:35.896 A:middle on plotted or hand drawings. 00:17:36.286 --> 00:17:38.786 A:middle Use only when it's important to show the function of the thread. 00:17:39.286 --> 00:17:40.736 A:middle If the main function of the thread is 00:17:40.776 --> 00:17:44.186 A:middle to simply put the pieces together, you don't need to go 00:17:44.256 --> 00:17:47.266 A:middle through the detailed representation. 00:17:47.266 --> 00:17:48.866 A:middle It's not typical for hand drawings, 00:17:48.866 --> 00:17:50.606 A:middle because it's very tedious. 00:17:51.426 --> 00:17:53.576 A:middle On the other hand, we also have the simplified 00:17:53.576 --> 00:17:55.266 A:middle or schematic forms. 00:17:55.266 --> 00:17:56.916 A:middle So a simplified is right here. 00:17:58.186 --> 00:18:01.636 A:middle And here's the schematic. 00:18:03.056 --> 00:18:08.286 A:middle So for the simplified, we imply the depth of the threads 00:18:08.376 --> 00:18:10.516 A:middle with hidden lines for the simplified representation. 00:18:10.516 --> 00:18:13.396 A:middle So they actually look like cylinders. 00:18:13.396 --> 00:18:17.306 A:middle And as a result, it can be confusing. 00:18:17.356 --> 00:18:20.196 A:middle On the other hand, for the schematic we use alternating 00:18:20.526 --> 00:18:24.636 A:middle long, thin, and short thick lines, like here, long, thin, 00:18:24.636 --> 00:18:28.586 A:middle and short, thick lines to represent roots and crests lines 00:18:28.816 --> 00:18:30.076 A:middle in schematic representation. 00:18:31.216 --> 00:18:35.256 A:middle Spacing schematic does not necessarily need 00:18:35.426 --> 00:18:37.346 A:middle to match the actual pitch. 00:18:37.566 --> 00:18:40.246 A:middle So this is simplified. 00:18:40.316 --> 00:18:46.306 A:middle This schematic is somewhere between the tedious detail 00:18:46.306 --> 00:18:48.286 A:middle and the oversimplified 00:18:48.286 --> 00:18:51.286 A:middle and sometimes confusing simplified representation. 00:18:51.286 --> 00:18:54.216 A:middle So comparing the two representations detail is very 00:18:54.216 --> 00:18:58.136 A:middle tedious to construct, and hence not commonly used. 00:18:59.436 --> 00:19:02.606 A:middle Simplified is fast, but potentially confusing, 00:19:02.766 --> 00:19:04.936 A:middle because the hidden lines can be mistaken 00:19:04.936 --> 00:19:07.606 A:middle at cylinders corresponding to all features. 00:19:07.966 --> 00:19:09.866 A:middle A schematic is best overall. 00:19:09.866 --> 00:19:10.586 A:middle It's balanced. 00:19:11.176 --> 00:19:13.266 A:middle It's fairly easy to construct, 00:19:13.266 --> 00:19:15.716 A:middle and yet you could really close the threads even though 00:19:15.716 --> 00:19:17.846 A:middle that those are not accurately shown.