Female thread, through

[Christy]

Hi all,

 

I would like to ask what does the symbol for a Female thread, through means. The inner whole circle, is it the diameter of the tap drill? ... what does the outer arc means?

[Jack_O'neill]

If it's like the pic highlighted below, then yes, the inner solid circle is the tap drill diameter. The dashed or hidden circle is the major thread diameter, and "through" means just that...the threads go all the way through the material so you could put a bolt in from either side.

[Christy]

thanks for replying. does the picture below means the same please?

 

[dbroada]

that is certainly the European symbol for a tapped hole.

[Jack_O'neill]

Europeans....if they're not driving on the wrong side of the road they're inventing new symbols that only they recognize:lol:

[JD Mather]

If the thread representation and tap drill diameter were drawn actual size they would be too close to show clearly on the drawing. Therefore the standard is to draw the major diameter actual size and the (for internal or external thread) and the tap drill size a nominal (in name only) size offset a distance sufficient to clearly show on drawing. See any technical drafting reference text.

[Jack_O'neill]

That's true for the smaller ones JD especially. 10-24 and smaller gets hard to see without an enlarged view, but the bigger ones aren't that bad. I've drawn them actual size forever. Got a lisp that pops the size i want in from a drop down list. If you put a leader on one that says "DR. & TAP 1/4-20 THRU n PLCS" or something to that effect that takes the guess work out of it.