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WHY DRAWINGS ARE IMPORTANT?
WHY DRAWINGS ARE IMPORTANT?
Communication:
Communication:
Engineering drawings are a critical component of the product design and fabrication/ manufacturing/ construction process. They serve as the essential communication tool for a component or assembly's dimensions, materials, features, and a host of other characteristics. The quality and accuracy of engineering drawings directly impact the fit, form, and function of the final product. A well-crafted drawing ensures that the product meets its design specifications and functions as intended. In contrast, a poorly crafted drawing can result in defects and errors, costly rework, and potentially dangerous situations for those building a part and the end user.
Legal Context:
Legal Context:
Effective communication through engineering drawings is essential to ensuring that everyone involved in the fabrication/ production/ construction process is on the same page and can succeed together. The drawing often serves as an essential defining element of legal contracts between parties. Many lawsuits have hinged around a vendor's/contractor's satisfaction of unclear engineering drawings. Attention to detail and proper use of this form language is therefore paramount when creating engineering drawings in order to avoid these types of issues all together.
Best Practices for Engineering Drawings
1. Drawings should be clear and uncluttered. Use a minimum number of views (Usually at least 2) that still allow for all features to be defined and dimensions.
2. Don’t dimension something more than once. Any double dimension that is used should be defined as reference placing it in parentheses.
3. Use symbols whenever possible instead of words.
4. Notes should be kept to a minimum. Any time excusive amounts of notes are required, a separate document should be used.
5. With a few exceptions, drawings should not detail the process to create the features. If required to outline how the part should be manufactured these details should go on a separate document often called a “Manufacturing Plan”.
6. With few exceptions Dimensions should be placed off the part and not on it.
7. Generally, when defining the location of features, dimensions should be coming from Datums unless there is a reason for the contrary like in the case where the distance between 2 holes is critical.
8. Where possible and practical Reference points (Datums) should be features that relate to the function of the part like a surface or edges that touches another part of an assembly or for example a hole that is key to the function of the part.
9. When determining the size of clearance holes for bolts and other fasteners use a chart or clearance hole calculator. These tools will allow you to pick the right amount of clearance for the application that will correspond to a standard drill size.
10. It is best practice to use all-caps for notes, etc., so turn on all-caps when you start to create a drawing.
11. Hidden lines should not be dimensioned.
12. All dimensions must have tolerance, either General, Specific, or GD&T.
13. Rev Levels should be kept up to date.
14. Use a standardized Template to save time and to give your drawings a uniform look.
DRAWING EXAMPLES
DRAWING EXAMPLES
Taped Block - Print.pdfThe above drawing is a good example of how to locate features. It uses the same 2 sides of the part as reference for the dimensions of for the location of each of the holes. The tolerance used is general tolerancing so 1 decimal place is plus or minus .100, 2 decimal places is plus or minus .010 , 3 decimal places is plus or minus .005. You will normally find general tolerances in the Title Block and are used when there is no other specific tolerance given.
Note also how the Tapped holes are called out. 1/4-20 UNC-2B is for a 1/4 inch thread-20 threads per inch, class 2B is a type of fit and tolerance. In this case it is a standard fit and tolerance.
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