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4" != 33cm ... ?
Somewhere in my "stuff" I have a couple foundry rulers calibrated to account for metal shrinkage as it solidifies. One for iron, one for aluminum... those will mess with your work if grabbed by mistake.
It looks (to me at least) like the rulers just aren't precisely lined up, but that the inch marks are at a consistent shift from top to bottom.Regardless of what increments are used, the whole inch marks should always align. They do not.
As noted above, always use the same ruler throughout a project.
The 2x4 is "dimensional lumber size". This is what came off the sawmill. Originally this was just used "as cut". Over time the variability of lumber from different Sawyers and different Mills caused irregular sizes, as things like door and window jambs were mass-produced, they needed uniform lumber.So why are 2x4 wood not 2" x 4" ?
I also still use them.Back in the dark ages, I took various drafting courses. A little after inscribing on clay tablets, but definitely before CAD.
I had 2 different triangular scales.
The architect scale was in 1/2, 1/4, 1/8
The engineering scale was in 1/10ths
Except mine were not color coded.
View attachment 612943
tape measures can stretch over their lifetime!
We found this at work one time with a 50' tape that had stretched about 3/4" over its use
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