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Sheet Tolerance format

NRDock

Cast Iron
Joined
Jan 24, 2015
Location
Central Pennsylvania
For most of my working life, we had a tolerance block on our drawing template defining default tolerances, unless specified otherwise. There were separate areas for fabrications and machining. The tolerances depended on the magnitude of the dimension within several defined ranges. Bigger dimension --> Bigger tolerance. We were all happy, and comfortable with this system.

Now, we're converting to model based drawings made in Inventor. Someone has saddled us with a sheet tolerance block in which the default tolerances depend on the number of decimal places in the dimension. So, now we have to code all our nonspecific tolerances into the dimension format. Everyone I work with hates this and thinks it's stupid. Where does this shit come from? Are others doing this? Can anyone offer a good reason for doing this?
 
Using default tolerances based on decimal places in common practice IME.

Like this:

(change values to fit the application)

.X +- .03
.XX +- .01
.XXX +- .003
.XXXX +- .0003

This ^^^^ to me makes much more sense than having a vague tolerance "based on magnitude". :eek:

It's not a big deal to change over, most CAD programs should allow you to Ctrl+click dimensions and assign decimal places to all of them in one fell swoop.
 
The tolerance varying with size was very common when we were dimensioning injection molded plastic parts. Every other place used the number of decimal places as the default tolerances. This is so common you will see comments on here that go, hey that dimension has 3 decimal places it must be a tight tolerance. No one has shared or seen the title block, it is just assumed that more decimal places means tighter tolerance.

When you get to model based dimensioning, we have a default note that reads, undimensioned features are CAD nominal +"profile of a surface XXX" (insert GD&T symbol here) relative to datums A,B,C. If you want tighter control than that you add specific dimensions.
 
For most of my working life, we had a tolerance block on our drawing template defining default tolerances, unless specified otherwise. There were separate areas for fabrications and machining. The tolerances depended on the magnitude of the dimension within several defined ranges. Bigger dimension --> Bigger tolerance. We were all happy, and comfortable with this system.

Now, we're converting to model based drawings made in Inventor. Someone has saddled us with a sheet tolerance block in which the default tolerances depend on the number of decimal places in the dimension. So, now we have to code all our nonspecific tolerances into the dimension format. Everyone I work with hates this and thinks it's stupid. Where does this shit come from? Are others doing this? Can anyone offer a good reason for doing this?

Your a professional, learn the new way, and make it work.

If not, India will gladly take your job for 1/10 the cost and dimension & tolerance it any way the customer wants it.

I used to routinely turn a fit on a 50" dia. ring to +.000 -.002

Your present tolerance system would not work in this instance.
 
Your a professional, learn the new way, and make it work.

If not, India will gladly take your job for 1/10 the cost and dimension & tolerance it any way the customer wants it.

I used to routinely turn a fit on a 50" dia. ring to +.000 -.002

Your present tolerance system would not work in this instance.

I've been grumbling about this at my kitchen table for months, but decided not to make a crusade out of it (Just over 400 days till retirement).
Lately I've been working with a designer who spent most of his career laying out whole mineral processing plants. I'm getting tired of telling him how many decimal points every dimension needs.

Your small rings get a specific tolerance and do not rely on sheet tolerances. I don't mind applying appropriate tight tolerances where they are needed. I'm complaining about having to code the tolerance into every dim on the sheet, when a magnitude/range system use to cover every dim that wasn't specifically toleranced.
 
Someone has saddled us with a sheet tolerance block in which the default tolerances depend on the number of decimal places in the dimension.
If it's not working for you then you need to have a discussion with "someone". If you don't know who "someone" is then change the tolerance block in the sheet format back to what you want and eventually "someone" will introduce themselves.

I suspect the "someone" who converted you to Inventor copied from a default sheet format template because default tolerance based on decimals is probably the most common format in the engineering world. It sounds like it's not a good fit for your industry, so change it. I'm not sure what the big deal is.
 
Often seen on old drawings in inches, fractional sizes +/- .001 decimal dimensions +/- .0001 example, magnitudes of scale depending on number of decimal places followed this, I first saw it in the late 70s so it’s not new, but it certainly catches people out who don’t actually read the print and assume it’s like the last one, plenty of room for mistakes, some costly.
It’s just easier for the drawing office or design office than individual spec
Which I prefer too btw, “if in doubt ask” suddenly became more common on drawings!,
Mark
 
I've been grumbling about this at my kitchen table for months, but decided not to make a crusade out of it (Just over 400 days till retirement).
Lately I've been working with a designer who spent most of his career laying out whole mineral processing plants. I'm getting tired of telling him how many decimal points every dimension needs.

Your small rings get a specific tolerance and do not rely on sheet tolerances. I don't mind applying appropriate tight tolerances where they are needed. I'm complaining about having to code the tolerance into every dim on the sheet, when a magnitude/range system use to cover every dim that wasn't specifically toleranced.
Sort of SOP with every drawing I make, and been doing it for over 30 years.

You need to get out more....I've done some architectural drafting, tool design, product design, even a small amount of whole plant layouts (different than building drawings, more using GPS coordinates) etc.

Too bad your not being asked to integrate the parts list inside the CAD file.
This latest trend is making releasing a simple part a multi day affair.

Everyone is different, they have their reasons, they are not "all wrong".

400 days to retirement ?

Might as well just quit now.
 
What's the problem?

Well I have to assume if OP is about a year or so from retirement, he's don it "this" way for so long he is just out of touch. I've never heard of stuff being toleranced by size? :nutter:

What if the giant bore is for a press/slip fit of a different component, does it just get toleranced +/- 1.00" because it is so big??? ... Everything about that seems wrong.
 








 
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