I have two doubts about the following drawing of the floor-side views of an object:

enter image description here

1) In the side view, does it need the horizontal line (a) in the union of the cylinder part with the prism? Or can it be omitted, because both sides are tangent?

2) In the floor view, is it necessary for the horizontal line (b), as if it was a hole?

  1. Preferably there should not be a line in (a), so it should be omitted. Note: You also have a second error in that projection. See, the plane should not cut the other half of the cylinder in either case.

    Originally it wasnt even allowed, but with the age of 3D CAD these restructions have been lifted and relaxed, it will probably be needed in some cases in future drawings. Ideally if you need this line, you would use a thinner line that does not touch the edges to mean that is it is a imaginary line of intersection (incidentally 3D CAD applications have a really hard time with this).

    • See ISO 128-24 01.1.1 Imaginary lines of intesection.

      enter image description here

      Image 1: You can use imaginary lines, in accordance to ISO 128-24, but they should not touch edges and should be thinner.

    • This is probably defined in ASME Y14.2 for the American market but i have no copy. Note: One can deduce that your most likely not in USA since you are using first angle projection!

  2. The dashed line in (b) should be avoided. It brings no value. In fact the whole projection should probably be omitted since it has no value at all.

    • For more on this see ISO 128-30
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  1. No, with exceptions
  2. No, with exceptions

If this diagram is conveying the structure or connective pieces of an item or product then maybe it is important for people to see the internal separation lines. If they only need to know about the solid block shapes then you don't need the internal lines.

You could include more information about which view is which (top, front, side). You can also make the images look more 3d with shadows or contour lines.

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  • 1. is allowed, and quite common today. It was not allowed back when i was in school but they have intentionally relaxed the standards. It is there rto faciitate next gen drawings that WILL need this line. – joojaa Jun 29 '17 at 6:50

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