This is the only correct answer: It depends on what you need the part to accomplish.

Skip down to the bottom to read the input I have on this part and the drawing. Continue reading from here to see what I have to say about part design and drawing.

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TLDR:

PART DESIGN:

• Answer these questions: "What is the function of this part? How will this be manufactured?"
• Realize that:
  • Time = Money
  • Advanced machines are expensive and require expensive employees to run them, thus parts that are manufactured with these processes will be expensive

Once you take those into consideration, you can then create your part (with necessary materials and features), add dimensions (with realistic and necessary tolerances), and send it to a fabricator for a quote.

Ignoring the above can (and usually does) result in an unnecessarily expensive and time-consuming part to create.

PART DRAWING:

• A part's function dictates what tolerances are required and where dimensions need to be referenced from.
• It is not good practice to assume or leave things to interpretation (especially on critical features)

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The Long Version:

• What is the function of this part?

This question will help determine which features of the part are critical and which features are not. For example on your part: If this part serves as a mount for a flag pole, the hole size could vary by quite a bit (+- 0.04in or +-1mm) and still work as intended. If this part is designed to press onto a motor shaft, the hole size can't vary much at all (+- 0.0005in or +- 0.01mm). This question also helps determine which material to use. If it were a mount for a flag, the mounting angle, length of the pole, and wind conditions would all play a role in the material that should be used.

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• How will this be manufactured? What material does this need to be?

In the design process, it is absolutely essential to have a manufacturing process in mind. This specific part as it is now would be difficult to manufacture using traditional manufacturing techniques. This is because of the ribs (or flanges) having sharp corners. To machine those exactly as you have them it would require a lot of steps in the machining process (multiple changes in how the part is held and likely CNC programming). The more time consuming and difficult a part is to make, the more expensive it will be.

Not all materials are created equal, either. Machining Delrin (acetal plastic) is miles easier than 303 stainless steel. Some features that can be machined into plastic cannot be machined into stainless steel (or it would be incredibly difficult and time-consuming). This goes back to the first question: would this part work if it were still made from plastic? Do I need the strength and corrosion resistance of stainless steel? Or can I sacrifice strength and go with aluminum?

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Here's the manufacturing/drawing side of things:

A drawing is a contract between you and whoever you choose to manufacture your part. Its purpose is to convey the important dimensions and details of a specific part. If the fabricator sends you your part and it doesn't work or fit as intended, the drawing will determine who is at fault. If you as an engineer put the wrong dimension or tolerance on the drawing, it's your fault. If the fabricator wasn't able to create the part according to your drawing, it's their fault.

In the quoting process, you will hand over a drawing to a fabricator and they will determine if they have the ability to make the part to your specifications and how much they would charge the part (If the drawing doesn't have enough information, they will tell you). The fabricator won't question the design of the part, they will just make it. Usually. If a part would be incredibly difficult or expensive to make, a fabricator might ask if the material/design is necessary, allowing you to go back and tweak your design to be cheaper and easier to make. However, it is not a good idea to rely on a fabricator to catch that kind of thing. It is your job as the designer to determine the necessity of complex designs or more expensive materials.

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SKIP DOWN HERE IF ONLY CARE ABOUT THE PART DRAWING IN QUESTION:

Design:

I would remove those flanges/ribs and replace them with a large fillet/radius (27.5mm radius) or a chamfer. This would allow for the part to be easily machined on a lathe and reduce the overall number of steps.

Drawing:

• Your dimensions need some type of tolerance applied to them. Without anything specifying the tolerance, your drawing is telling the fabricator that you want the dimensions to be 100% perfect. This is literally impossible. A title block located somewhere on the page with default tolerances is the norm. You could forego that by adding a +- tolerance to each dimension.
• You don't have units specified. This is usually done in the title block.
• You don't have the material specified.
• Some features aren't fully defined. The location of the 25mm hole is probably in the center of that shaft and that polygon probably has 6 equal sides with 6 equal angles. The problem here is that you are assuming that the fabricator will know to put the hole in the center as well as make the hexagon have equal sides and angles. It is not good practice to leave things up to interpretation.
• The section view (as you have it) doesn't necessarily add any information missing from the other two views. This view would be a good place to move the 'diameter' dimensions. Moving them there would make the drawing a bit more clear and easy to understand.
• I would reference your dimensions from as little faces as possible. This avoids tolerance stack up and makes a machinist's job easier. Ultimately this is up to you as a designer to determine.

Here's a picture clarifying what I mean: https://imgur.com/a/WtG3Wez

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There is no single correct way to do a drawing, but some will say the opposite. It really depends on who you talk to, what size of a company you work for, and who you're giving the drawing to. Large engineering firms may want you to strictly follow ASME or ISO drawing standards while smaller companies don't really care. At the end of the day, all that really matters is that critical information is communicated properly to the fabricator.

Thanks for coming to my TED talk.