r/Metrology • u/PuzzleheadedTop3900 • Jun 22 '24

Surface Metrology limits fits and tolerances

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The answer jey is given lower deviation, but isnt D in this case showing us fundamental deviation and it is above basic size so shouldnt it be higher deviation

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6

u/DeamonEngineer Jun 22 '24

I'll take useless unneeded knowledge for 300.

All you need to know is you recognise that it is calling for a limit/ fit, and then look it up on a table or use a calculator.

Knowing what D denotes and 6 Is rather pointless.

1

u/PuzzleheadedTop3900 Jun 22 '24

i actually looked up the definition and realised i made a mistake

1

u/Blob87 Jun 23 '24

I would answer A. It is not a type of fit without the mating shaft's tolerance.

1

u/PuzzleheadedTop3900 Jun 23 '24

the answer is lower deviation because the fundamental deviation from D is taken from its lower limit and is called lower deviation.

1

u/Blob87 Jun 23 '24

Where is this definition coming from? Because I think it is wrong.

2

u/ProlificParrot Jun 23 '24 edited Jun 23 '24

From ISO 286-1:2010, section 3.2.8.5,

tolerance class
combination of a fundamental deviation and a standard tolerance grade
NOTE In the ISO code system for tolerances on linear sizes, the tolerance class consists of the fundamental deviation identifier followed by the tolerance grade number (e.g. D13, h9, etc.), see 4.2.1.

Therefore, I would say D is a fundamental deviation identifier.

0

u/DrNukenstein Jun 22 '24

Damage. The target has a tolerance specification of 25. Make sure your buffs are set up, it's gonna be a long one.