# SU7 and tolerances

OK, I got use of a computer with XP and have been learning SU7. Pretty cool. As a kid, I worked just long enough as a carpenter to be dangerous, but not to read blueprints. Now I'm trying to create some. As a mechanical CAD designer, I'm used to working in thousandths of an inch. I'm sure that level of accuracy is not needed for architectural drawings. Or is it?
Main question. When I'm creating detailed drawings of the deck I'm repairing, do I create them using nominal dimensions (2"x4") or actual dimensions (1-1/2"x3-1/2") for lumber? Seems like it should be the later, specially for cutting to length. What kinda tolerances are typical for framing and the like?
nb
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On Sat, 06 Jun 2009 20:40:35 -0600, notbob wrote:

Draw all the members actual size (not nomimal). Make general dimensions work out to the inch, and details to the nearest 1/4" or at least 1/8". It also helps to understand the nominal sizes for materials so you don't pay premiums for having to buy the next biggest size (e.g., floor joists 12'-2" long require splices, intermediate girders, or buying 14' long members.)
--
Steve Hall [ digitect dancingpaper com ]

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I always design in actual dimensions. I always create my buy list in nominal dimensions. I usually configure my design program to draw in numbers divisable by 1/16th's to conform to 1/16" tolerances.
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Use actual sizes for the materials and cut lengths to the degree of accuracy that you want to build. The hardest part is remembering to use "Architectural Lettering" vs. Mechanical Lettering. I took architectural drafting after mechanical drafting and had a hard time learning to be sloppy with my lettering. IMHO architectural drawings were closer to "sketches" when compared to mechanical drawing. ;~)
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I was fortunate in that I had a machinist teacher who was fanatical about knowing fraction and metric equivelents. As close as I get to bilingual. ;)
nb
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snipped-for-privacy@bb.nothome.com wrote:

Woodworking machines may be built to 1/1000 of an inch, wood work is measured in 1/16 or 1/32 of an inch. I measure everything in 1/16th because I can't see 1/32, so I use 1/16th + or -, which probably gets me around 1/32. when drawing stuff up to build, 1/16th is all I need.

Wouldn't make any sense to draw something up using wood dimensions that existed before the lumber was dried and planed to final size? If you are using 6" lumber for the floor, and need 50 pieces, you will be off by 25" if you pretend the lumber is 6" wide, and not 5 1/2". Ordering the lumber you of course use the rough cut dimensions.
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Jack
Go Penns!
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snipped-for-privacy@bb.nothome.com wrote:

Use actual dimensions, except when ordering materials ... if you do not, your drawings will be inaccurate.
Normal tolerance in framing and Architectural/construction drawings is 1/8". For woodworking drawing you will usually be OK with 1/16", but you can go down to 1/64 using Architectural dimensions, and 0.000000" with Engineering dimensions:
Model Info|Units to set your Unit tolerance preference for the project.
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www.e-woodshop.net
Last update: 10/22/08
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