From: MV (MV@dc9.tzo.com)
Date: Fri Nov 18 2005 - 07:55:25 PST
That's good advice. I have never had much luck with easy outs either.
I once had to drill out an exhaust manifold bolt from a Chevy 454 engine
without removing the head from the engine. It was just below the
surface. That was a tough one. The bolt was very hard and I ended up
buying a special TIN drill bit (not very popular at the time) meant for
CNC machining. Even that bit had to be resharpened a couple of times
before I could get the drill through the broken off stub. Once I got
the bit through I was able to pickout the remaining threads with an awl
and a tap. The entire process took several hours.
Some shops have EDM machines that can eat out broken bolts and studs
without damaging the surrounding material. It tends to be expensive,
but if you have a bolt broken off in an aluminum casting that costs a
small fortune it can be well worth it.
If a bolt is broken off just above or below the surface and is not stuck
hard, you can sometimes use a 3" abrasive wheel cutter with a thin wheel
and slot the broken off stud and use a big screw driver to back the stud
out. If you can weld a nut on the broken stud and then heat the
surrounding material which expands and try not to heat the stud, that is
the best situation. But if the stud gets too hot it will simply twist
off when you apply torque, so you have to use the heat very carefully to
minimize the heat on the stud iself. Cooling the stud with water while
heating the surrounding area is sometimes a good idea also.
To get bolts and nuts loose that are stuck, careful use of a cutting
torch torch to heat the assembly is hard to beat. Of course iron
castings can crack and or warp from the excessive use of heat.
Dave
Buzz wrote:
> Listers,
> To remove broken bolts on old equipment I assume that the bolt is rusted and
> that's why it broke. Especially head bolts, or studs, that go into the water
> jacket. I don't like using heat because that plays havoc with the temper of the
> metal. I've never had much luck welding on nuts because I couldn't get the
> proper penetration. Speaking of penetration, penetrating oil will break the
> surface rust bond, but after a week it only penetrated a few threads. If I can
> get the bolt or nut to move a little then I add more penetrating oil and work it
> in and out a little at a time until it comes off.
> Back to the original problem.... get the drill. If the part is broken off below
> the surface I use the proper size transfer punch to punch it exactly in the
> center, then follow up with a regular center punch. I usually start with a
> center drill, then a SHARP 1/8" drill. I use enough force to remove material but
> not so much that I bend the drill. If too much force is used the drill will
> bend and go off center.
> I then start using left hand drills 1/16" at a time, up to just below the tap
> hole size. If the piece is still in the threads then I tap the hole. Usually
> what happens is that as I approach the size of the broken piece it'll spin out
> of the hole.
> Forget about eze-outs they just break, then your in REAL trouble. The only time
> that I've had good results with eze-outs is if the bolt was new and broke from
> over tightening, or was sheared off. If I use eze-outs I like the square ones.
> The left hand threaded ones seem to swell the bolt then it is tighter.
> Buzz
> BTW buy a GOOD set of drills because if you come up against a class 8 bolt
> you're gonna need a good drill.
>
>
>
> On Thu, 17 Nov 2005 13:31:35 -0600, you wrote:
>
>>What would you do when you have one like the one being discussed that is
>>broken off up in the threaded hole?
>>
>>Sonny
>
>
>
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