The name and contact information for the company producing or distributing the part The name and contact information for the engineer who created the drawing The name of the object or part, along with part numbers or other identifying information The units of measurement used for dimensions in the drawing[5] X Research source The scale of the drawing
If you have any questions, follow this information back to the person who approved the changes and find out why the changes were made and why they approved them. The information in the revision block can be extremely important if you’re involved in a contractual dispute with a manufacturer or a buyer of a product you manufactured.
For example, if the object requires screws, the bill of materials will list the part number for the screws along with the size and length so you can gather them. The bill of materials allows an engineer to maximize space in the drawing by including dimensions for small parts in a separate block. For more complex objects with lots of parts, the bill of materials might be a separate page. If you’re looking at engineering drawings with an unfamiliar system of measurements, check the ANSI/ASME equivalency tables. [8] X Research source
For example, if keynote 1 is “concrete masonry,” every instance of concrete masonry on the drawing would have a 1 in a circle to identify that material. For more detail about the makeup or configuration of the material identified in the keynotes, check the specification for the object. Unlike keynotes, general notes apply to an entire set of engineering drawings. They typically provide information related to a particular discipline that helps an engineer of that discipline better understand or interpret the drawings. For example, general notes applicable to a civil engineer would be listed under “general civil notes. " Avoid assuming what a symbol means and always double-check or ask if you’re confused by something. [12] X Expert Source Perryn OlsonConstruction Specialist Expert Interview. 3 August 2021.
Typically, a solid line with an arrow connects the symbol and its corresponding value with the line on the drawing it applies to.
If the value has a line underneath it, the finish should be done by a machining process. A value with a circle under it indicates that the surface must be finished without removing any material in the process.
LH/RH: left hand/right hand ID/OD: inside diameter/outside diameter MAX/MIN: maximum/minimum CL: center line C to C: center to center FAO: finish all over STL/CS: steel/carbon steel
For example, if you’re looking at an engineering drawing for a fluid power machine, you might see any of 113 symbols for equipment, 93 symbols for valves, and 74 symbols related to hydraulic pumps and motors.
Some drawings might place the dimensions directly on the side of the object if it’s clear in the drawing what side that dimension refers to.
Check the units of measure being used to make sure you have the dimensions correct, especially if you’re looking at an engineering drawing drafted in another country. [21] X Research source If you see an “=” over a line, that indicates the dimension is the same as that of a parallel side. [22] X Research source
If you see 2 dimensions given, that means you can construct that portion of the object to be any value between the maximum and minimum value. The value you use might impact the dimensions of other parts of the object, but the object will function correctly as long as all dimensions remain within the tolerance.
You might also see a dashed line or cross to indicate the center of the circle, particularly if the part is designed to rotate.
For example, an engineer drawing an extremely small object might enlarge it for the purposes of the drawing to show necessary detail so the object could be recreated. However, the dimensions listed on the drawing still correspond to the dimensions of the actual object.
Hidden line: made by dashes; indicates an edge hidden behind the solid face of an object Phantom line: made by a series of dots and dashes; indicates an alternate position for a moving part Center line: made by a series of lighter long and short dashes; indicates the exact geometric center of the object Break line: made by a solid line with zig-zags; indicates part of the object is excluded from the drawing
If the drawn object is opaque, you can’t see its internal workings simply by looking at a drawing of the outside of the object. To show internal components that are necessary for the object to function, engineers draw cross-sectional views. Depending on the type of object, a cross-sectional view might not be necessary. If there is no cross-sectional view, you can assume that the object is hollow on the inside.
For example, if the object is opaque, you won’t be able to see the interior of the object from the outside. When you imagine the object in your mind, put the drawing of the interior inside the object and imagine yourself turning or opening the object to view the inside.
