Date:         Fri, 17 Nov 1995 17:30:52 -0600
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         mbushore@icaen.uiowa.edu
Subject:      re: Bolt Extraction


Steve Maher writes:
I've often wondered: when a bolt has been jammed so tightly into a hole
(by cross-threading, rust, wring thread or whatever) that someone was able
to put enough torque on it to break it clean off... what makes anybody
think that it can suddenly be removed by an easy-out that's one-third the
diameter of the bolt, and tempered so hard it's brittle?

Does anyone have ANY success stories involving an "easy-out" that's actually
WORKED? Or are these gadgets the mechanical equivalent of Slick-50?

 
	The relative "brittleness" of the easy out has no real bearing
on its ability to remove the bolt, other than insure that it will be harder
than whatever you are trying to remove.  Presumably the heat treating the made it
so darn hard to begin with will also push its yield strength up so that it has
the neccesary strength in shear to handle removing the other bolts.
 
	On the other end of the stick, you mention that the easy out only
has about 1/3 the diameter of the bolt it is trying to get out.  You would
probably have a lot more problems if
1) The material properties of the original bolt hadn't been changed by cumlative
   fatigue damage and thermal cycling
2) The original bolt hadn't been drilled out at all.
 
	Fatigue is going to (usually) weaken the bolt that you are trying to get
out.  Since the Easy Out is new, and likely heat treated to a high strength, right
out of the package, although it is seeing a higher stress, the material properties
haven't degraded, and it can come out.  Sometimes this isn't the case, and for
numerous reasons, the Easy Out breaks, too.

	Drilling out the center of the bolt should decrease the force in the
fit between the tapped hole and the bolt, depending on the situation.  If its just
rusted in, I don't think it would be significant.  If it were something like a tapered
pipe fitting, then it would be.
 
 
How does this jive with others feelings/observations?
 
	If any of this doesn't make sense for any reason, let me know..

Matt