Effective Threaded Hole Depth

[Fairway]

Is here a quick reference to effective threaded (tapped) hole depth? I realize this may be dependant on the grade of bolt used, pitch etc. Just looking for a quick reference or formula that may give some understanding.

Thanks!

 

[desertfox]

Hi Fairway

I very often use thread depth = 1.5 X bolt dia
usually for steels, as you say if it was a soft material
it may be 3 or 4 times bolt dia.

regards

desertfox

 

[KENAT]

As DF says 1.5 X bolt dia is rough rule of thumb for non critical (or whatever phrase covers it) threaded holes.

Sometimes expressed as 1 to 2 X diameter of bolt.

However, this is reall rule of thumb stuff.

KENAT, probably the least qualified checker you'll ever meet...

 

[Fairway]

Thanks team. I always new the "rule of thumb, just looking for simple way or reference to validate it.

Thanks again!

 

[Timelord]

fairway,

Another opinion: I always use the 2X bolt diameter that my CAD program (Solidworks) defaults to. The 1.5X rule of thumb is based on the typical strength of threads and is a bolt engagement rule, not a tap depth rule. Going to 2X usually means I can find a standard length bolt that gets at least 1.5x engagement in the hole.

Timelord

 

[KENAT]

Good point Timlord, it's the engagement that's important. The hole length just needs to be deep enough to accomodate this allowing for tolerances.

I always work back from my fastener & material thickness to work out my hole dept then normally round up to the next 'round' number and make it a "min full thread" call out.

As to validating it, I believe there have been threads (no pun intended) about that before, if not on this forum then maybe forum725. As I recall it my old stress man used to talk about the first few threads taking most of the load...

KENAT, probably the least qualified checker you'll ever meet...

 

[hydtools]

Here is a reference from engineersedge:

http://www.engineersedge.com/thread_strength/thread_minimum_length_engagement.htm

It relates fastener tensile strength to thread shear strength.

Ted

 

[desertfox]

Hi Timelord

I read effective thread as meaning thread engagement.

Regards

desertfox

 

[cb92]

As a machinist, keep in mind that regular taps have a tapered start, and need room at the bottom of the hole for chips. You don't want the tap bottoming out, you might break it. A bottom tap will finish off a hole deeper, but it's another step, and bottom taps dull quicker, and are even more sensitive to bottoming out.