Topic: Is ignorance bliss?

[Kate M]

Just out of curiosity -- what do you all set your precision to? At some point, is not knowing if something is really 3 63/128" instead of 3 1/2" (as it should be) unimportant? I'm asking because it bugs the heck out of me to not know for sure *exactly* how long my lines are, but there's been a small debate here because half the drawings we use as backgrounds weren't drawn precisely to begin with. So when we trace over them (getting walls off arch drawings, for example), nothing exactly adds up. So do you make it work? Or do you fudge it by setting your precision to 1/4" and not worry about anything else?

[CAB]

I have 2 dim styles I switch back & forth.
I use 1/64 as my accurate one & use it to do most things.
I get drawings from time to time that I use my 1/4 on and
sometimes that is not enough. So i try to fix what I can.
I wonder if some of those folks are drawing free hand???

When I dimension the centers if reinforcing on the foundation
I use 1/2 because the centers of the dowels are +/- 2" & I'm
too lazy to move the dowel blocks or they abut an opening
that pushes them off my target dimension.
When I draw houses I don't like to see any fractions but
1/2 is ok  at times and 1/4 is rare. If you get below that they
laugh at the drawings in the field. I know I used to be there.

I dimension my interior walls to the center & make sure my dimensions
are to the inch. Dimensions to the exterior wall are to the exterior
face and the foundation is done on block modules (10'-0' 10'-8 11'-4")
So I avoid the fractions.

My 2 cents.

CAB

[hudster]

We use metric so set to 1mm tolerance.

not much point in going below that when it comes to building layouts.

[Keith™]

I use 1/16 precision, and occasionally find that a dimension is off 1/64 or even 1/128 but it is rare. In the architectural field, if you use anything less than 1/4" on your drawing as cab stated, they will look at your plans and laugh at you....

The 1/16 precision I use is to make sure the drawing I have is correctly drawn, and exactly drawn...not just drawn "good enough"

Personally I would recommend against tracing over drawings, but if you do, I would recommend that you trace them to a close tolerance using the snap grid set to a precision you feel comfortable with. At least this way, if the original line is 3 43/128, you can have it snap to 3 1/4, 3 3/8, 3 5/16 or whatver degree of precision you want.

[CADaver]

We set the dimunits to 1/16" for dimensioning, but the unit precision is set to 1/256".  As you work with larger unit precision, small errors begin to creep in that can and do compound upon themselves until the error shows up in a dimension somewhere or something is noticably out of square.

[CAB]

As you work with larger unit precision, small errors begin to creep in that can and do compound upon themselves

Speaking of small errors, it is also better to work closer to the origin when you can.

Precision Errors

[t-bear]

I guess I'm wierd but I *DRAFT* to 0.00000000 and *DIMENSION* to the nearest 1/16th.  The shop doesn't need any closer tolerance than that with the exception of drill sizes to */32....  I have found that doing 3D it is necessary to hold to 8 decimals or I get in trouble with extrusion paths for piping runs etc...  Just what works for me.

[CADaver]

Speaking of small errors, it is also better to work closer to the origin when you can.

That'd be nice, but we draw on absolute coordinates from the survey.  If we're lucky the plant is using a local coordinate system with the origin somewhere in the same state as the plant.  But very often we're set to USGS coordinates. :crazy:   That's when UCS ORigin and SNAPBASE become extremely useful.

[Keith™]

T-Bear, I am with you..... I draw to 0.00000000 but I too dimension to 1/16...

Don't you hate it when you have a line that when you zoom as close as possible it looks like it touches, but it really doesn't. Then you find out that the line was off by 0.00000004

Especially when trying to hatch an area....

[t-bear]

Keith....
It took me a while to get in the habit of setting my units to 8 points (I'm a sloooowww learner) but doing so sure has made life easier.  Even 0.00000001 will screw you up.  Been there, done that, got the t-shirt!  The bummer was always tryin to figure which of the eleventy-fourteen lines was off!!!

[Keith™]

What about a line you try incessantly to extend only to be told there is no intersection in that direction... then you find out that the line was drawn at 0.0000004 degrees from 0 and precision is set to 0.00 ....

Incedently my drawings are my product, and I am proud of my drawings. All the connecting lines and such....not everyone can do it...

[t-bear]

I've gotten in the habit of using plines whenever possible.  Did you ever draw a "straight" line in plan view, then change to an iso only to find that your line is off in BFE somewhere?   Frustrating as all git-out.  A pline stays parallel to the x-y plane.

Incedently my drawings are my product, and I am proud of my drawings. All the connecting lines and such....not everyone can do it...

I feel the same way.  I'm not ALWAYS perfect, but I try damned hard to be.

[ELOQUINTET]

well me i'm in metal fabrication so my dimensions at set to 1/32. i usually also set my units to 1/32 but if i'm doing layout i set it to 1/256. i also set it to this precision if i'm working on someone elses drawing. we do alot of custom metal and glass work and have to follow all the other trades essentially covering the mess to put it kindly. when we get the architecturals we most often bust out laughing. the concept is kinda there but they have no idea how things are fabricated or installed. sometimes i wish i could work at a firm so i could just cut and paste details from catalogs. ok i'm ranting...

[Keith™]

.... cut and paste details from catalogs.....

That pisses me off to no end....
Companies develop their blocks and details for use in the industry but fail to put thought into the drawings and they fail to use any sort of precision....
I almost never use them....although I have found Simpson and USP to be pretty good about their drawings. Most fenestration manufacturers however have very poor quality drawings.

[t-bear]

I'm in 3D  (did I mention that?) and my pet gripe is all these mfgrs who haven't bothered to look into 3D parts.  Oh there are a lot of nuts-n-bolts type crap out there but the major players (Gardner Denver blower mfg. comes to mind) can't be bothered.  I've had to convert some of their 2D dwgs to 3D models....even showed 'em to their rep.  He was impressed, but said the company couldn't be bothered.  They give us a "generic" layout and a dim table to work from.  When I have a lead time of two months on a blower, I need the piping ready to mount when it *finally* arrives. It can't be done right without a true 3D model.
I'm sure there have to be other companies in the same spot I'm in.

[Keith™]

I am sure.....