Min Internal Thread Engagement Length

[whtan02]

Hello everyones.

I'm new in this forum.

I have a question on screw tapping hole.

If drawing only specify M2.5, what is the thread length here? Do we have a standard calculation here?

With Unified screw, it's engagement length is specified in a standard no. of thread per inch.

Then I wonder what is the standard for metrice thread?


Thank you very much!!

[jboggs]

Please check your words. You ask for thread length, which means the distance from the first thread to the last thread. Then you mention "thread per inch". That is thread pitch, the distance from one thread to the next. Which do you want: thread length or thread pitch?

In my experience with metric threads, if no pitch is specified, assume standard coarse pitch.

[whtan02]

Please check your words. You ask for thread length, which means the distance from the first thread to the last thread. Then you mention "thread per inch". That is thread pitch, the distance from one thread to the next. Which do you want: thread length or thread pitch?

Thanks for your reply, jboggs.

In my experience with metric threads, if no pitch is specified, assume standard coarse pitch.

I'm asking for the standard of thread length (min engagement length).

I'm sorry to create the confusion.

[PinkertonD]

I'm with JB, it is very unclear what you are after, but, if it is thread engagement the a rule of thumb is a minimum of one diameter.

However it seems more likely that you are after Pitch in which case, if omitted in ISO it is the Pitch for a standard course thread, in your case, M2.5 x 0.45

BUT - it is always best to check back with the customer as they will be the one rejecting 20,000 items you have just machined with the incorrect pitch.