Paul Amaranth >
> Some people claim to have removed bolts just by using a left hand drill
> bit. I have never personally witnessed this one either.
I am one of those people who so claim. The original idea is that if you
are going to use an EZout, it makes no sense to tighten the bolt with the
drill when you go to make the necessary hole. So a left-handed twist
drill is used to prevent this. What I have found is that often (not
always) the vibration imparted to the bolt by the drilling can shake up
the rust and loosen its grip. If this is in a place where you can get
some penetrating oil in there, the vibration and heat help to get the oil
to migrate into the rust. The torque of the drill motor happens to be
in the correct direction to back out the bolt if this happens. I have
found that in almost every case, if the drill does not remove the bolt,
then the EZout won't do the job anyway! If his occurs, at least you are
on your way to drilling the thing out completely so you can retap it. If
you are very lucky (I have to be lucky, because I am not that good with a
drill motor) you can drill right out to the tap drill size and retap the
same tread size in the original threads. If not, you have to drill
oversize for a larger bolt. If this is not practical, like it is a head
bolt or something, you have to drill oversize for a HeliCoil or other type
threaded insert. Remember to tap cast iron DRY.
The bottom line is, if you have a bolt broken off in a blind hole, there
is no disadvantage to using left-hand twist drills instead of regular ones.
And you may get lucky and pop the sucker right out.
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