Does it make sense to make a tolerance that does not exist in the tolerance tables ?

[LCform]

Hi All

I am trying to use the tolerance standards more appropriately and with more sense, but regarding to the work we do , that is for the different machines that we have , we happen very often to be obliged to replace a broken piece. for example I see that sometimes tolerances like -+0.01 are chosen , that for fit and precise running, I did not find any, but it seems that they do that by experience or feeling ?! is there any way to reason that if such a tight tolerance is not ok and for example a H7/g6 is a better one?

 

[SwinnyGG]

Your wording makes it a bit difficult to determine what exactly you are asking, but if a part or feature needs to be controlled for a certain type of fit, such as a slip, sliding, running, assembly fit, etc, I ALWAYS use fit tables for this. They were designed for this exact scenario, and they remove guesswork and mistakes. I would never substitute a simple geometric tolerance for a fit.

 

[djhurayt]

your "wording" . . .

 

[ctopher]

See Machinery Handbook.

Chris, CSWP
SolidWorks '16
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SolidWorks Legion

 

[KENAT]

The fit tables don't cover every eventuality, you need to determine based on function what you need.

Certainly on any interference fit, the insertion forces, induced stress in the mated parts, different material properties and other factors may work against simply using the standard limit & fit tables without any extra thought.

In theory using the standard fits should conform to available tooling, ground shafts, mating parts... but varies in practice.

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(probably not aimed specifically at you)
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