Prioritize clarity when preparing drawings

- [Instructor] Before we dive into the nitty gritty details of choosing views and placing dimensions, we're going to outline some general guidelines for successful mechanical drafting. In this video we'll discuss the importance of making clear, complete drawings, the reason your drawings should be process independent, and why it's important to have others check your drawings before releasing them. Making good engineering drawings is really all about good communication. You have to assume that whoever is making your parts knows nothing about how they work or what features are critical to their function. Engineers use drawings to clearly communicate exactly what has to be delivered and the amount of deviation from the perfect geometry that is acceptable. It's critical that engineering drawings are complete and have all the dimensions and views required to make the part. If something isn't defined on the drawing, it probably won't be on the final part either. A lot of engineers assume that most machine shops use CNC machines, so the machinist will just ignore the drawing and program the machine from the CAD model. Well, the reality is that even today a huge amount of prototype and even some production work is still done on manual machines, using paper drawings. Even when a shop has CNC machines, it is often faster to program them manually using the drawing instead of using CAM software on the computer. A subtle note is that engineering drawings must communicate exactly what needs to be made, but not how to do so. For machine parts, in particular, there are usually a few different ways that a given part or feature can be made and the manufacturer should be free to choose the most economical method available to them that satisfies the stated tolerances and requirements. To help you better understand what we mean here's an example. This drawing of a clevis specifies a diameter and the word ream. Reaming is a manufacturing process that uses a special fluted cutting tool to machine a hole to a precise diameter. The engineer probably said ream, because they wanted the hole to be machined to a very tight tolerance. Reaming is certainly an acceptable way of machining this feature, but each reamer is only able to cut a single size hole. And since is a fairly unusual diameter the shop is unlikely to have the required size. They would have to order a custom tool, which will add to the cost and lead time to make this part. Instead, the engineer should just specify the acceptable tolerance for the hole, then the machine shop is free to use another more flexible technique, like boring or circular milling. Plainly said, it's not the engineer's job to tell the machinist how to make the part. Finally, it's important to always have your drawings checked by somebody else before releasing them for manufacturing. Sometimes views and dimensions on the drawing will seem obvious to you as the designer, but will be confusing for everyone else. Having your drawing looked over by a second set of eyes will help prevent this. Ideally, the checker would be an experienced engineer or drafts person, but even a peer review will provide valuable insight. Oftentimes the best feedback will come from the machinists themselves. If you work at a company where the manufacturing happens in-house take some time to ask the machinists and quality inspectors what they prefer to see on drawings. To summarize, we've emphasized that clear, complete paper drawings are still critical, even for the most modern of machine shops. We've shown you why an engineering drawing shouldn't specify any specific manufacturing process. And finally, we've discussed the importance of getting somebody else to review your drawings to be sure they are clear before you release them to manufacturing.