Gallery, Projects and General > How do I??

Drawing interpretation

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vtsteam:
Maybe your explanation is clearer for someone.

I also picture metric in translation, multiplying millimeters in my head by 4, and then dropping a couple zeros to get a visual idea of roughly how many inches are being talked about. I'm sure that if I had to do that more often I'd gradually be able to picture metric sizes without that.

Well, I do picture a centimeter as-is and for some reason 6mm, probably because of familiarity with plywood thickness. So I'm a little bit mentally mongrel!

SwarfnStuff:
Yep, we all have tricks that help us get the general idea and a lot of drawings seem to come from the USA and therefore imperial rules.

Here in OZ we are metric BUT if I am coming out of a bank for example, there are often markings on the exit 4,5,6,etc with sub marks indicating the 6" bit. My guess is that most still think of a person's height in feet and a half?

Suppose that will fade with younger generations, who knows?

Something else I needed to get my head around is Third Angle Projection (think that's what it is) as I grew up with Plan, Front, Right or Left Elevations where the view was as if you walked around the part or building.
  Until a fellow model engineering club member said to imagine the part in a salad bowl. Looking straight down you see the plan. Slide the part to the right or left and as it slides up the bowl you see the respective view. Similarly sliding the part up the front or rear gives those views.

I was a textile dyer by trade so this modeling caper took me back to my Tech Drawing classes at secondary school. Amazingly I still remembered lots of it.

Hope my above waffle makes sense and helps some.  :mmr:

vtsteam:
I still think in naval architectural terms: profile, plan and sections for the lines. Often the sections are overlaid onto the profile view at midsection, forward half sections on the left, aft half sections on the right.

Historically, all this came from the early way of designing hulls, carving a half model out of the solid made of plank "lifts" doweled together. When separated the lifts were traced around on paper to yield "waterlines" in the plan view. The flat face of the assembled half model was traced around for the profile. Section lines were erected in plan and profile to get points (offsets) to interpolate the sections, and then these were drawn in with battens (splines), ducks (weights). and curves either on paper or full size on a loft floor. Diagonals were erected to check the offsets. Making sure that all offsets corresponded in all views, with no unwanted humps or hollows was called fairing. The whole thing was a painstaking process. Computers make fairing easier now. But you still need an "eye" to do something pleasing and worthwhile.

djc:
I know this is a few days old and you have your answer, but it is possible to use a measuring device on the drawing to confirm or deny your suppositions.

A piece of paper laid over the 3/4" dimension on the left side and marked both ends, then folded in two and marked again will give you 1 1/2". Lay the 1 1/2" over the supposed 1 1/2" on the right side and see if it lines up.

No paper? Use your thumb over the 1" + 3/4" on the left. Same thumb on the right would be slightly longer than zero to 1 1/2" and massively longer than 1 1/2" to 1".

If your supposition of adding the dimensions were correct, the total would be 3 5/16", putting the last hole well over to the left of a part that is only 4" overall long.

Look at the vertical dimensions of the first three holes. They are identical to the horizontal ones.  The third one appears to be in line with the centreline of the material. A straightedge along the three hole centres would show they align, meaning vertical and horizontal  dimensions are identical.

This is not to make excuses for a drawing whose dimensioning leaves a bit to be desired but you can use other features of the drawing you have to sanity check or infer or clarify things as necessary.

John Rudd:
Yup, all done...
I went with gut instinct and used the tlar rule...

Hopefully have the job finished by the end of this weekend... :dremel:

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