Bottoming out threads of blind hole

[BenjC]

I'm trying to find some guidance of the behaviours of load and stress distributions on threads when a bolt is bottomed out against the base of a blind threaded hole and pre-load is applied. Are there design guides that elaborate on this topic? Do bolts that bottom out the threads of the hole hold torque? If not then why?

 

[Jboggs]

Bolts in standard tapped holes really do not bottom out on the bottom of the hole. They "bottom out" when their threads encounter the partial threads at the end of the thread. So-called "bottoming taps" will provide a fuller thread all the way to the end of the thread. But I still think a standard screw probably wouldn't actually touch the bottom of the tap drilled hole, which will have a 118 degree conical shape anyway.

Either way, I wouldn't count on a "bottomed out" screw to provide much in the way of torque resistance.

 

[hydtools]

A screw bottomed out will not create a joint preload. It can remain in place, as with a stud screwed in to a housing, serving as mounting fastener for a flanged mating piece.

Ted

 

[desertfox]

Hi Benjc
Bolts and screws shouldn't really bottom out because that could relieve all the preload on the parts being clamped.

“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein

 

[drawoh]

BenjC,

How does a bolt bottom out in a hole? Does the end face hit the bottom of the hole, or do the threads jam as the tapped hole runs out?

You could tap through a plate, then screw a face plate to one end of the hole. This gives you an abrupt bottom to your tapped hole. What does the end of a typical commercial off the shelf screw look like? How thick will your face plate be?

--
JHG