Doubts in an object view

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

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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.

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      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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