Draft: definition of hole depth

[Gnome121]

General question regarding threaded holes in draft:
Assume a part with a face, and a pocket in that face, and a blind hole in that pocket... confusion !
Is the depth of the hole referenced to the topmost face or to the pocket face ?
I guess this makes a big difference wether the machinist first machines the pocket vs. the hole.
Or should I maybe place a datum frame and refer to that with a callout ?
Need to get this right so I don't get parts machines all wrong, how do I do this correctly ?

 

[bshand]

Perhaps the only way to be sure is a side view, maybe a section through the hole, with dimensions.

 

[beachcomber]

It's from the face you created the hole sketch on.

bc.
Core i5-3570 @3.4GHz , 8GB RAM
Quadro FX4600. W7 Pro 64-bit.

 

[Gnome121]

beachcomber: Yes that seems the only logical way of doing it.

I have lots of holes in various places that even though they are drilled THRU, the thread depth is the (my) standard 3D...
But only a couple of extra turns on the tap and the thread is THRU the hole

Is there a symbol that can be used in the hole table to indicate minimum thread depth in tapped holes ?
This so the shop have the option to thread THRU if they prefer to do so.

I can pass the info as a note in the table but an accepted symbol would be 'cleaner' I think.

 

[bshand]

"Is there a symbol that can be used in the hole table to indicate minimum thread depth in tapped holes ?
This so the shop have the option to thread THRU if they prefer to do so."

Typically in my experience holes that are not to break thru are labelled explicitely so. Perhaps you could make a shop rule to that effect.

 

[KENAT]

"Is there a symbol that can be used in the hole table to indicate minimum thread depth in tapped holes ?"

I'm not aware of one in the drawing standards, so even if SE (or you) invented one people wouldn't understand what it mean unless you train all your vendors or at least have an explanatory note somewhere.

Why not just do the time honored and put "MIN FULL THREAD, MAY BREAK THRU" or similar?

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[beachcomber]

Maybe I misunderstood the question.
I thought you were asking where the hole start reference was in the model.
You can place a hole on any plane, even one offset by a distance from the surface of the part.
Hole depths are then measured from the hole sketch plane.
Now I realize you are talking about drawings, so the reference is usually the face of the part.

I'm not aware of any special symbols either.
Normally I would indicate either a through hole (preferred) or a blind hole according to the design requirement, and not leave it to the machinist.
I would also explicitly define the thread depth for a blind hoe, and tap all the way through a through hole.

bc.
Core i5-3570 @3.4GHz , 8GB RAM
Quadro FX4600. W7 Pro 64-bit.