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  #1  
Old 03-03-2021, 11:09 AM
salty salty is offline
 
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Default How to read engineering drawings

When reading the left side of figures 3 & 4, is there an assumption that the part is sitting flat with the angled portion of the part extending toward you? I can't see any cues on the drawing that makes that certain, but I'm no engineer, I don't know if this is always an assumption or something.

You could also be looking at the part from the flat side with the angle extending away from you, which in this case, would matter since the part isn't symmetrical.

I'm just curious if I'm missing something, whether it is on the drawing, or a convention I'm not aware of.
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  #2  
Old 03-03-2021, 11:25 AM
rapid_ascent rapid_ascent is online now
 
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These drawings are usually based upon the X, Y, Z coordinate system. Different views are usually based upon rotating the part 90 degrees. Normally the view is perpendicular to the part in the basic views. This is a very standard way of showing different aspects of a part.

Think of having the part in your hand and rotating 90 degrees then that is what you would see. If it is a horizontal rotation normally the view is drawn to the side of the part. If it is a vertical rotation the view is normally drawn above or below the part.

I am an engineer and I have often wondered about the difficulty of someone who doesn't have any background at looking at mechanical drawings with learning this skill.
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  #3  
Old 03-03-2021, 11:26 AM
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For 3 view drawings like this, you can interpret them as if the part was sitting in a bowl (or half sphere). Take the lower left drawing and assume it's on the bottom of the bowl. Slide it up the bowl away from your , look down from the top, and you get the top left projection (90 deg rotation on one axis); slide it from the bottom to the right rim and you get the bottom right projection (90 degree rotation on the other axis).

You can do this experiment with a "real" part to get the feel for how the three projections are done.
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  #4  
Old 03-03-2021, 11:36 AM
PhatRV PhatRV is offline
 
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This is how I read the drawing.
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Old 03-03-2021, 11:43 AM
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My instructor in High School Drafting class had us visualize rinsing a dish under a water facet, "all drawings you make in this class will be laid out this way.

We all could relate to this method as we grew up washing dishes after the dinner meal.
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Old 03-03-2021, 11:46 AM
tjo tjo is offline
 
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The easy way is if the flange was facing away from you, it would be hidden from view by the back of the part. As a hidden line it would be dashed. if the flange was coming out toward you it would be a visible line, and therefore would be solid. In this case it is a solid line, so it is coming out at you.

Tim
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Old 03-03-2021, 11:56 AM
terrye terrye is offline
 
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Default How to read engineering drawings

My high school instructor had a very intuitive teaching aid. It was a three panel frame with screen within the frame. Each panel was square. Flattened out, it formed an 'L' shape, with a hinge where each panel met the adjacent one. With the frames folded, it took on a cube shape, of course with the bottom, left side and back missing. An object was placed in this partial cube, and looking at the object through each screen, blackboard chalk was used to draw the shape of the object onto the screen. When the panels were unfolded, the object was depicted as it would be in the drawing we would make of the object.

This is called third angle projection and is the convention in North America, and is the projection shown in the OP's picture of the Vans bracket.

A further explanation of the orthographic and isometric views is shown in the Construction Manual page 03-06
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Old 03-03-2021, 11:59 AM
David Paule David Paule is offline
 
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It isometric view is a bit confusing since it doesn't show the short flange with a tapered face. It shows a part that's symmetric, and the other views don't.

Dave
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Old 03-03-2021, 01:02 PM
salty salty is offline
 
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Quote:
Originally Posted by tjo View Post
The easy way is if the flange was facing away from you, it would be hidden from view by the back of the part. As a hidden line it would be dashed. if the flange was coming out toward you it would be a visible line, and therefore would be solid. In this case it is a solid line, so it is coming out at you.

Tim
This is a good tip. I felt that might work, but I wasn't certain.

Now, a followup question.

What's the purpose of the dashed line running parallel, but very close to the solid line on the right side of the bottom left drawing in figure 3? I get the purpose of the dashes on the flange at the bottom, as they indicate the little kickout, but why do they go all the way up the part?

My guess is just to provide context. It makes it more obvious than if the dashed line where only on the flange, but does it mean something more?
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Old 03-03-2021, 01:06 PM
salty salty is offline
 
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And another, slightly different example of my confusion. In this particular case it doesn't really matter because the cuts are symmetrical.

However, it's still interesting to me because my wife held the part up one way and I held it up the other and we both said it matched, and after I looked at it closer, I realized we were both right. Nothing on the diagram indicates if the bend is towards or away from you.
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