ot - 5g thread class

[kkominiarek]

Can someone explain to me please?

 

M12 X 1 5g (external thread)

 

I know that the 5g indicates the tolerance class for the pitch diameter.

 

But......is there any numbers to this tolerance?

ex: 5g pitch diameter tolerance = +.1mm / +.15mm

 

What is the difference in size or tolerance between 4g 5g & 6g?

 

I searched mach. handbook and internet, I could not find any hard numbers for tolerance.

[mold100]

Ken I found the tolerances in the mach handbook25th edition page 1689-99 I think.

Lots of numbers not exactly sure what I am looking at Dman numbers are foriegn to me.

[mold100]

Looks like for 1.0 pitch external

 

mill tols are

 

fit met english

4 .112 .0044

5 .180 .007

6 .280 .011

 

I am not positive may need 2nd opinion

[F. JAVIER]

Can you make sure that the tolerance class is 6g instead of 5g?; It could be a typo by the engineer in charge.

 

Good luck.

f. Javier

[iowajim62]

Hi Ken,

G is for Ground Thread

4,5,6 are classes of thread pitch diameters above or below Nominal. Generally H is for High, L for Low, ex.,M12 x 1.0 GH4 is Basic plus .002 to Basic plus .0025. HTH

[mold100]

Jim thanks, I havent read that far into the book but I am getting there, See one person asks and it helps more.

[kkominiarek]

thanks for the quick response....unfortunatly I only have the MH 24TH edition (soon to be 25th)

 

I keep looking in the 24th edition...but I can't find.....I'll keep looking.

[Philcott]

Ken,

 

In Metric thread designations "G" and "H" designate the tolerance positions for the lower deviations of internal threads . The "g" and "h" designate the tolerance position for the upper devistions of external threads .

 

Phil

[sbrooks]

The "G" is for external threads and the "H" is for internal.

[CAM-mando]

The Number represents the amount of tolerance, the Letter is the "Position" of the tolerance relative to the basic pd (id / od).

 

The book I have only lists: 6g and 4g6g. 4g6g means the pd is 4g class and the crest is 6g so the pd listed for that should be the same as a straight 4g.

 

M12 x 1 6g

pd = 11.324 / 11.206

 

M12 x 1 4g

pd = 11.324 / 11.249

[CAM-mando]

Upon further inspection ...

 

I checked my ring gages and I have ring gages with 6h on them. Heres what I have found:

 

The number as stated above is the class of tolerance.

 

The letter as stated above is the "position" of the tolerance relative to basic. This does not neccessarily mean internal or external. For example in an interference fit the external thread could have an "h" position pd.

 

What indicates internal vs. external is whether the letter is uppercase or lower case.

 

Uppercase is internal thread.

Lowercase is external.

 

This concludes my report

 

CAM

[kkominiarek]

Thanks again all!!!!

[kkominiarek]

Thanks again all!!!!