# Orthographic project (section view) dimensioning a counter bore?

The following question was given in a book as an autocad assignment. The section depicted in the diagram is not a counter-bore or a spot face hole. But the professor is telling that the hole is a counter bore.

This is the correction suggested by the professor in the blue pen. This is the section view of the front view along of A-A line. Is the correction correct as I argued that this not true.

• Hard to say as we are not seeing the written part of the assignment text. Therese also extra dashed line in your image that is not in the isometric image. Commented Mar 6, 2016 at 11:43
• @joojaa Yes the dotted lines should not be there. It is a kind of a custom made assignment made by the college professors. I am kind of tired of this. Commented Mar 6, 2016 at 14:59

The original drawing is ambiguous. There is no hidden line showing that the individual holes are counter bores. The portion of the drawing that is cut out also is in the area where the other portion of the counter bore would be shown. It could be clearer.

All of that being said, there is one way that you could assume that each of the holes has a counter bore: Look at where the dimensions are drawn from. The dimension shown in the cut out is drawn from the centerline of the hole. This would only make sense if it was dimensioning the radius of a counter bore. The dimension is connected to the centerline of the small hole even if the only dimension is to the outside of the part.

The end result is that the original drawing could be clearer, but without a counter bore, the dimension given doesn't make sense.

• So the professor is being a little bit of a jerk. I could not see the counter bore and showed it to him right in fornt of him. He could not locate it, but was smarty enough to mark with the blue pen right? Commented Mar 6, 2016 at 14:57
• It would say "tricky" as professors tend to be. Like I said, even the way that you drew it doesn't completely make sense since there is a line on the dimension going to the centerline of the hole and not the centerline of the part.
– hazzey
Commented Mar 6, 2016 at 15:00
• Yes the dotted line part in the section view I agree was a mistake on my part but the hole thing is what irritated me. Commented Mar 6, 2016 at 15:02
• @Vinay5forPrime So did you come here to vent or to get help?
– hazzey
Commented Mar 6, 2016 at 19:55

You are correct. There isn't enough information to suggest a counterbore.

Figure 1. Part view from rear.

Figure 2. Section view.