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I have to draw a part sectional view of a valve for a project. A 3D view of the valve is supplied and a line AB denotes where the part section is to be. It says:

"The part section is to be to the left of AB"

Does this mean to section part of the area left of AB and not section the right of AB. Or does this mean to section all of the area left of AB and not section the right?

Thanks.

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A picture of this question would be quite useful, or a scribble something like it.

But I'm assuming the line is drawn on a 2D drawing of the part. Imagine that this part is lying on the table in front of you so that you see the exact same view of it as drawn. If you take a super sharp knife and cut along the dotted line AB, all the way down the piece like cutting a potato in half, that's your section. Then you take the LEFT piece and place it so that you are looking at the cross section you just made. Then you draw this.

You cut the part all the way along the dotted line, so if this extends all the way through the part, you draw the part as above. However, if it extends part way though, it's like you made the cut (all the way down to the table, but not all the way through the potato) and then tore off the right chunk - you'll have a section view for part of it, and a complete view for the rest of it, with an interface in between where you've torn it.

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Although a line is the conventional way to indicate a section it may be easier to visualise it if you think of it as a plane passing through the line. If you are asked for a left or right section this indicates that the plane is vertical, top or bottom indicates that the plane is horizontal.

This plane can be thought of as cutting the part with one side or the other effectively ceasing to exist as far as the drawing is concerned.

The purpose of this is to show internal detail of an assembly or part and is common for complex core castings, engines, gearboxes etc where internal parts may be contained within a casing.

In some cases actual parts may be physically cut as illustrative tools for museums and teaching aids eg http://previews.123rf.com/images/gortan123/gortan1231212/gortan123121200016/16859227-Automatic-gearbox-cross-section-on-black-Stock-Photo-transmission-automatic-car.jpg

Here the red pained parts are material which has been cut by the sectioning plane.

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