Most likely you are dealing with someone in the US. Anyone else would have called for just M2.
That would be a metric standard (coarse). What ever else he wanted to say is everybody's guess.
Standard M2.
Kenat - could be. Since he is using a small "h" I believe
he is talking about an external thread and they come as
4h, 6g, 6e and 6f. Since no number before the "h" is listed
my guess is that this is just a standard M2. In drawings from the rest of the world that is how it would appear.
Just M2 and that is how you would buy a tap. Drill size would be 1.6mm. Unless this thread if very special or a "Fine Thread" - than more information would be required.
If it is a U.S. drawing it could not hurt to double check - I have seen drawings with a lot of unnecessary and confusing information - just because the designer had limited knowledge and wanted to be on the very safe side.
in my interpretation m2 x .4 is M2x0.4 preferable choice metric thread (where 0.4 is thread pitch)
Letter h can specify tolerance grade for external thread but it follow with digit always.
Ak762 - you are quoting ASME and ANSI correctly - not ISO
To simplify metric thread callouts, the international (ISO) standard for metric threads eliminates the pitch callout on coarse threads. For example, the thread "M10" automatically means a coarse pitch, while any added pitch callout, such as M10x1.25, specifies a non-coarse pitch. This method of designation has the major benefit that average citizens do not need to memorize pitches just to identify a coarse thread.
Virtually all thread standards across the world use the ISO designation convention, including the German DIN and Japanese JIS standards. All except the ANSI standard, which so far still asks for a pitch callout on coarse threads, despite the confusion that it causes.
Thank you all for your responses. I will contact our customer. As you all have stated I believe their intent was to specify the tolance for the fit but not enough information given in regards to the class ie the number 4,5,6 and also these are female threads so the lower case h also seems to be in conflict. Again Thanks all!
