Yield Strength vs. Center Hole Diameter

[sburstall]

I am looking to add a counter sink hole through the center and almost the full length of a 10-32 stainless-steel, threaded stud. Short of experimenting, is there any information out in the web about computing the yield strength to the counter sink hole diameter?

 

[MikeHalloran]

Huh?



Mike Halloran
Pembroke Pines, FL, USA

 

[rb1957]

do you mean you're drilling a hole down the shank of the bolt, and it has a CSK end ?

i'd expect to knock-down the tension/shear allowables based on the reamining X-section area.

 

[sburstall]

Sorry, the hole will drilled down the length of the shank. Maybe counter-sink/bore was describing it incorrectly.

I'm just looking for some kind of paper/analysis about how the diameter of the hole will effect the strength of this bolt/stud.

 

[drawoh]

sburstall,

The term "stainless-steel, threaded stud" does not tell us much. What kind of stud it is? What kind of stainless steel is the stud made of?

I don't think any of us understand the problem. I size countersinks to the diameter of the flat head fastener I am putting in it.

A 10-32UNF thread has a minor diameter of around .156". This makes for a small countersunk screw. I cannot imagine anything bigger than 2-56UNC (Ø.086") or M2x0.4 (Ø.079").

JHG

 

[BiPolarMoment]

It sounds to me like he is intending to have a threaded fastener with a (axial?) thru hole--potentially to allow flow (of what?) thru it. From a theoretical point of view I would expect it to reduce the strength by the equivalent of the hole cross-section.

e.g. if it's a .01" hole and you are looking at purely tensile loading I would hope to see a reduction in yield load of (material yield strength)*(3.14)*(.005"^2)

So for SS316 @ 35000 psi yield strength I would expect the bolt to yield(in pure tension) approximately 2.8 lbs earlier than without the hole (essentially subtracting the strength of a .01" wire).

The real story is not quite this simple, but is that what you are looking for?

Hopefully I didn't just have a brainfart and I got my ideas straight.

 

[dhengr]

I don’t think you should drill that hole in the threaded stud, because all the yield strength is likely to leak out of the stud if you do.

 

[MikeHalloran]

Clearly OP has never worked with banjo bolts.


Mike Halloran
Pembroke Pines, FL, USA

 

[racookpe1978]

Well, last week I was working with a 3 inch diameter 19 inch long series of studs with with a 9/16 hole down the center of each for heating and stretch measurement as the studs were tensioned.

But a nbr 10 screw? Better experiment. If not for the screw strength but for the best way to drill the little bitty hole through the screw without breaking the drill off midway through.

What dia hole? What stress on the screw? Shear or tension or both?