need information concerning metric drawing

[theonics]

My company is currently working on parts from German drawings. The following callout n25 H7 is used several times. I know the 25 is mm I know the H7 is class of fit. what I can't find out is what n means.
thanks

 

[gearguru]

What feature is dimensioned that way? It could mean "Nabe" - like an diameter in an internal spline. (The H7 tells you that it is an internal feature, ISO fits use the capital letters for holes/internal features.)

 

[juergenwt]

Theonics- Your tolerance is a hole tolerance. Capital letters are for holes. H7 is position and quality.
In your case: 25H7 = 25mm -0, +21. Quality H7 can be achieved by reaming.That is -0.000mm, + 0.021mm.
My advise: If you are in the machining business - study DIN/ISO 286. Google it! You will need it.

Go here for more info:

http://www.wisetool.com/fit.htm

Good luck.