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SI units tol 5

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ctopher

ctopher

Mechanical
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How do you read these tolerances?
Not sure how to add this symbol here, but "<_" is "less than or equal to".

x<_10, +/-0.1
10<x<_100, +/-0.15
100<x<_500, +/-0.25
500<x, +/-0.5

If a dimension is 165 or 22.5, what tolerance is used?

I have never used this type before.
Thanks.

Chris
SolidWorks 10 SP5.0
ctopher's home
SolidWorks Legion
 
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ctopher,
I am very sorry, I must be confused about the subject of your initial post:

"How do you read these tolerances?"

"I have never used this type before."

I thought you were refering to ISO type tolerances.
Frank
 
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ISO 2768-1 gereral tolerancess to be more specific, I think I am so in a hurry to discuss them with someone that I read it in here where it was not intended.
Frank
 
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Frank,
What do you want to discuss about ISO 2786-1 in particular? It is still too general subject for a discussion. There is also 2786-2. Is it something you wanted to talk about too?
 
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pmarc,
I believe the determination was made, basically by concensis, that the general tolerances must be accumulative if you are looking at a worst case stack-up? Do we have any validation of that outside of our own conjecture?
There are also ISO standards covering casting and welding that are similar. These seem much more realistic to me than what we use and I am interested in the opinion of people who use these to they find if it works well for them?
Frank
 
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I did not mean to hyjack ctopher's thread. I thought he was asking about ISO type tolerances.
The ISO discussions could go here:

thread1103-298244

Frank
 
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pmarc If you want to discuss ISO 2768 again I suggest a new thread, and if you choose to do it in a forum far away from here that would be find by me too. ;-)

Posting guidelines faq731-376 (probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​
 
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Kenat, I am not the one who seems to be more determinated to discuss about it.

Unfortunately for me, but fortunately for you, no further posts about ISO 2768 showed up in this or other thread on the forum. :-)
 
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I've seen this type of tolerancing a number of times. Not to re-open the 2768 debate here, but to me it does tie in. As indicated previously, this system assumes that as a feature increases in size, its tolerance must be increased. Going back to older machines & controls, I would have agreed. With modern equipment's glass scales and encoders with ridiculously high precision and no length compensations, I don't think those numbers are realistic anymore. I saw data from a 6-foot capacity lathe that held the same +/-0.001mm capability as a lathe producing parts of 11mm diameter. It raised a red flag for me early on about 2768's scope of use and its dated assumptions / basis.

Jim Sykes, P.Eng, GDTP-S
Profile Services TecEase, Inc.
 
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Agree MechNorth, for molding/casting etc it makes a lot of sense but I'm not convinced it's universally applicable to machined parts any more (if ever).

In fact, whether features are done in the same set up is perhaps more of a factor these days.

Posting guidelines faq731-376 (probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​
 
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I apologize for resurrecting this thread.
This subject keeps popping up here and there is still confusion.
If I have dims 10, 10.2, and 10.425, what are the tolerances per the tol block?

I get mixed answers. I'm not used to these type of tolerances as displayed per ISO.
IMG


Chris
SolidWorks 11
ctopher's home
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A dim of 10 gets ±0.1

A dim of 10.3 gets ± 0.15

A dim of 10.425 gets ±0.15 (or ±0.150)


John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
 
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10 +/-0.1
10.2 +/-0.15
10.425 +/-0.15

----------------------------------------

The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.
 
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If it's greater than 100. That means even one micron over 100 would get a tolerance of ±0.25 (at least per Y14.5 paragraph 2.4; I presume ISO also sees dimensional limits as absolute).

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
 
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The concept: "greater than or equal to" is not solely an ISO concept, it is just mathematics.
Frank
 
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Good point Frank. I was just worried that some people will measure a number of 100.00001 and round it off to 100, thus giving it the ±0.15 (when it should really get the ±0.25 tol).

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
 
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Doh! Cancel that last post. I forgot that we're talking about dimensions -- as in intended dimensions -- not actual, measured size.

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
 
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