# What is causing the elliptical shape around the marked hole?

## Background

So I am looking at this piece titled "Ring" and I cant figure out what I am missing in the drawing that cause the elliptical shape at the two hole entrances on the right side of the drawing and the half ellipse in in the section cut.

Close up of oval in right portion of drawing:

Oval shape in section?

## What I have tried

When I modelled it I wound up getting this:

Since this is not my field of expertise, the only thing I could think of something like a grinding wheel taking a rounded chunk out at each hole.

## Question

Aside from scaling the drawing, does anyone have ideas what is causing the oval shape, and why it would be there?

# Update

Isometric views as requested:

• Probably because the hole is drilled perpendicular to one surface but that second surface is not perpendicular. Jun 23 at 6:50
• @SolarMike I agree that what you are describing would generate an elliptical shape. Why would you wind up with a circle in the middle of the ellipse? I had actually considered that for the sloped holes, but the ellipse was in the wrong direction. Jun 23 at 6:54
• What happens if you have two circles that intersect at an angle? then consider at which angle you view it from? Jun 23 at 7:09
• @SolarMike The inner holes that are put in at an angle, show the path of the hole which does not allow for left right boring angles which would generate the ellipse Jun 23 at 7:17
• Why would you need "boring angles" ? Jun 23 at 7:18

Very rough image:

A cylinder, or hole through an object when viewed on the axis looks like a circle, or rectangle when perpendicular to the axis.

But at an angle to the axis then the ends of the cylinder show a "curved" end - due to the viewing angle.

The effect of your hole going through curved surfaces shows the cuts as the dotted lines you are concerned about.