Understanding Tolerance terms

[caliper]

I've recieved prints for quotes which, in the title block, contain the following lines: "Tolerances unless otherwise specified: Internal Dim. -H12, External Dim. -h12, Rest +/-IT11/2" Does anybody know what this means and where it comes from?
Thanks,
Bill

[RICHARD ZASTROW]

Google ISO 1829

Dick Z

[mc-motorsports]

Sounds German, or atleast European. Are those tolerances for press fit or slip fit parts? I've seen similar.

[juergenwt]

For ISO Tol. go here:http://www.roymech.co.uk/Useful_Tabl.../ISO_Tol_T.htm
or here:http://www.tiefbohren.info/Buchstabe...oleranzen.html

These are the basic tol. numbers as per ISO 286.
The first one in English is still under construction. The second one is in German.
The numbers are self explanatory.
On one side of the table you will find the IT number and on the other side the nominal range (dim). Go down to IT11 and over to 50-80 (2 inches fall into this range) and you will find a total tol of 0.190mm. In your case +/-0.190mm.
I suspect your drawing was made in the US since they give the range of 2 inches and not 50-80mm.
For internal H12 and external h12 go here:http://www.engineersedge.com/iso_tolerance.htm
ISO tolerances are used all over the world. Time to download and to study.
All dim's are metric and in 1/1000 mm.
Post here if you need any help.

[jfrandsen]

That's good advice.

[tnik]

Hate to piggyback on a thread, but it fits..

Just got a print, and it tells me :

Dimension Tolerance Linear/Angle and Radius according to IT.EP.0024

Now I have found a few charts with the IT dimensioning, but can't find anything over IT-18..

Anyone else seen this?

[juergenwt]

Tnik - Can you post the part of the print that has all the spec's?

[tnik]

Tnik - Can you post the part of the print that has all the spec's?

That has all the spec's?

I don't have any specs, thats why I was asking about it.. only thing it says in the tolerance box is to reference IT.EP.0024

[juergenwt]

Sorry - I am not able to be of any help to you.

[RICHARD ZASTROW]

IT.EP.0024 may indicate the company standards for whoever originated the drawing.

For example: International Tinkering Engineering Practice version 24

Just a guess.

Dick Z