JoeSpareBedroom wrote:
wrote in message
ups.com...
I over-torqued four bolts in the lower unit of an outboard, and the
heads of three bolts broke off. I managed to remove one of the broken
bolt using a Dremel tool and a diamond grind bit. But I cannot remove
the other two broken bolts using the Dremel tool. Based on the past
posts in this newsgroup, I learn that the best option in this situation
is to drill out the broken bolts. I would like to learn the details of
the way to drill out the broken bolts. My question is:

Which size of drill bit do I need? Should it be as large as the hole
where the broken bolt is?


Call around to hardware stores and ask if they sell spiral screw extractors.
Before you jump in the car, measure the diameter of the bolt shafts you need
to remove. And, if you know the socket size that fits the heads, write that
down too.

I tried that already. Either it didn't work or I went too easy on the
hammer. Anyway, it could not grab the bolt and could not spin the bolt
out. I attempted to drill one of the broken bolt away. But this
simply messed up the thread in one of the hole.

Finally, a copy of the Mercury Service Manual arrived last night. I
read it and realized that the water pump base could be removed just by
removing 6 bolts, and each broken bolt went through a threaded hole in
the water pump base into another threaded hole in the lower unit. Seem
like the threaded holes in the water pump base had some chemical
reaction with the bolts, and the threads in the hole in the water pump
base had completely corroded away (the thread on the bolt mating with
the threaded hole in the water pump base was also corroded away
significantly and that was part of the reason why the bolt head broken
off easily before the thread got damaged by being over-torqued). In
other words, the water pump base was not holding on the broken bolt,
and only thing that was holding on with the broken bolt is the threaded
hole in the lower unit, and I can remove the water pump base easily.
After I had removed the water pump base, I could see a large section of
the broken bolt sticking out in the open, and I easily removed them
using a channellock plier.

Is this a happy ending? Not really. In the attempt of drilling out
one of the broken bolt, I ended up messing up the thread in one of the
hole in the lower unit (the other three are fine). I don't know what
is the best way to deal with this. I will bring the lower unit to a
marine mechanic in this afternoon to see if he can help.

The other thing is that I can simply replace the water pump base and
the broken bolts, and this should take care of the corroded threaded
holes in the water pump base. But I am wondering why the holes and the
bolts can get so corroded. The bolts must be stainless steel, right?
I didn't know that stainless steel bolts can react to casted alumimum
lower unit. How should I prevent this problem from happening again?
Any idea? Thanks.

Jay Chan

wrote in message
ups.com...
JoeSpareBedroom wrote:
wrote in message
ups.com...
I over-torqued four bolts in the lower unit of an outboard, and the
heads of three bolts broke off. I managed to remove one of the broken
bolt using a Dremel tool and a diamond grind bit. But I cannot remove
the other two broken bolts using the Dremel tool. Based on the past
posts in this newsgroup, I learn that the best option in this situation
is to drill out the broken bolts. I would like to learn the details of
the way to drill out the broken bolts. My question is:

Which size of drill bit do I need? Should it be as large as the hole
where the broken bolt is?


Call around to hardware stores and ask if they sell spiral screw
extractors.
Before you jump in the car, measure the diameter of the bolt shafts you
need
to remove. And, if you know the socket size that fits the heads, write
that
down too.

I tried that already. Either it didn't work or I went too easy on the
hammer. Anyway, it could not grab the bolt and could not spin the bolt
out. I attempted to drill one of the broken bolt away. But this
simply messed up the thread in one of the hole.


Hammer????????

David Scheidt wrote:
wrote:
:I over-torqued four bolts in the lower unit of an outboard, and the
:heads of three bolts broke off. I managed to remove one of the broken
:bolt using a Dremel tool and a diamond grind bit. But I cannot remove
:the other two broken bolts using the Dremel tool. Based on the past
osts in this newsgroup, I learn that the best option in this situation
:is to drill out the broken bolts. I would like to learn the details of
:the way to drill out the broken bolts. My question is:

:Which size of drill bit do I need? Should it be as large as the hole
:where the broken bolt is?

The best way to do this is to get a selection of left-handed drill
bits. These have the twist going the opposite way from a normal twist
drill. You have to run your drill in reverse to drill a hole with one
of these. That means, in addition to puting a hole in the bolt, you
apply some anti-clockwise force to the bolt, which may back it out.
Start with a small bit; drill exactly in the center, exactly
perpendicular to the hole. Then move up to a bigger bit, and repeat.
Increase the size of the bit until you're using a bit the size of the
minor diamter of the bolt (the diameter of the round part of the
bolt, minus the threads.). Then you can use a pick to pick the
threads from the bolt out of the threads in the hole. You could also
drill a hole, and try an EZ-out.

There's a better description he
http://www.dimebank.com/tech/BrokenBolt.html

:Related questions:

: The bolts are for securing the water pump housing for the
:impeller. The hole for the bolt is at the edge of the water pump base
:-- meaning that one side of the hole is kind of thin -- something like
:3/32" thick. The bolt itself is like 1/4" or slightly larger. Because
:I have over-torqued the bolts, I found that the holes pretty much losed
:most of the thread. If I drill out the bolts, I probably will find
:that the holes will become even larger. If I re-thread the hole after
:drilling out the bolts, I am afraid that the holes will be even larger.
: I am afraid that there will not be enough metal left. Is my
:estimation correct? I am wondering whether I may be better off somehow
ouring in new metal into the holes and drill new holes instead of
:rethreading/enlarging the existing holes?

There are thread inserts, called heli-coils (that's the brand name of
the original, and best, there are others), that may solve this problem
for you. The hole needs to be drilled oversize, roughly to the major
diamter of the hold hole, and then it's tapped for the insert. The
insert is a coild of wire that allows the use of the original sized
fastener.

David

As mentioned in my other reply, I have removed the broken bolts by
simply removing the water pump base. And I also attempted to drill out
the broken bolt; but I could not get the drill bit to center on the
bolt because the bolt was sunk inside the hole and I could not see the
surface of the bolt that well. This ended up messing up the thread of
the hole. Hopefully, the heli-coils will fix this problem. Thanks.

Anyway, I will bring the lower unit to a marine mechanic later in this
afternoon, and I will see how he will fix the thread in the hole.

Jay Chan

Which size of drill bit do I need?

I can't really answer this question without knowing the sizes of the
bolts. For example, the ideal sizes for a 1/4-20 thread would be a #7
drill. Different thread and different sizes would require different
drill sizes.

Should it be as large as the hole
where the broken bolt is?

Yes, BUT it means the size of drill that will fit in the hole where
there are good threads.

Thanks for the tip of selecting the right kind of drill bit. Although
I didn't need to drill the bolts out because I got them off by removing
the water pump base, I may find your tip comes in handy if I get
another case of broken bolts.

Somebody with expertise in this area needs to physically examine what
you have. It is really impossible to give quality advice without
seeing the exact problem(s).

Yes, indeed. And this is the reason why I will bring the lower unit to
a marine mechanic to have it fixed (to fix a threaded hole that I
messed up).

Jay Chan

Clams Canino wrote:
I wanna know how you broke *three*.
I mean - after you broke one... didn't a clue rake at least try to hit you
over the head about the rest of them?

Actually, I could have broken all four -- instead of merely three. I
must have come to my sense when I was bearing down on the 4th bolt.

I have a tendency to over-doing anything (such as running my knee to
the point that I needed to have a surgery done on my knee). And
tightening up the bolts too much is one of my tendency. That was the
reason why I bought a torque wrench hoping that using the torque wrench
will prevent me from over-torquing the bolts. Unfortunately, I mistook
60-inch-pounds with 60-feet-pounds, and I ended up over-torquing the
bolts by 12 times. And the fact that the torque wrench that I use is
quite big (designed more for higher torque such as for torquing the
propeller); therefore, I didn't get a good feel of the tension. I have
ordered a 1/4" torque wrench that is designed for lower torque (such as
60-inch-pounds); hopefully, this will prevent me from making a similar
mistake.

Jay Chan

wrote in message
ps.com...
Clams Canino wrote:
I wanna know how you broke *three*.
I mean - after you broke one... didn't a clue rake at least try to hit
you
over the head about the rest of them?

Actually, I could have broken all four -- instead of merely three. I
must have come to my sense when I was bearing down on the 4th bolt.

I have a tendency to over-doing anything (such as running my knee to
the point that I needed to have a surgery done on my knee). And
tightening up the bolts too much is one of my tendency. That was the
reason why I bought a torque wrench hoping that using the torque wrench
will prevent me from over-torquing the bolts. Unfortunately, I mistook
60-inch-pounds with 60-feet-pounds, and I ended up over-torquing the
bolts by 12 times. And the fact that the torque wrench that I use is
quite big (designed more for higher torque such as for torquing the
propeller); therefore, I didn't get a good feel of the tension. I have
ordered a 1/4" torque wrench that is designed for lower torque (such as
60-inch-pounds); hopefully, this will prevent me from making a similar
mistake.

Jay Chan


1/4" for 60 ft lbs.....hang on a minute. Who makes a 1/4" drive wrench with
60 *FOOT* lbs in its range?

Frogwatch wrote:
Frogwatch wrote:
Ernest Scribbler wrote:
"Clams Canino" wrote
I wanna know how you broke *three*.
I mean - after you broke one... didn't a clue rake at least try to hit you
over the head about the rest of them?

Not to jump on the jump-on-Jay bandwagon (he's got enough trouble with his
broken bolts already), but wasn't he the guy who asked what the difference
is between foot pounds and inch pounds a while back?

Good Lord, give him credit for trying to do his own work. So he makes
expensive mistakes, I bet he learns from them. I have managed to break
5 drill bits in rapid succession.
Now, If I remember, there are special tools for removing broken bits or
taps. I suggest he look into a tool catalogue such as McMaster-Carr or
MSC.

I have several tiny hardened end mills from MSC. They are no wider
than a screwdriver blade and cost about $20 each and I have used them
for such tasks to get down into a bolt hole (using the dremel tool) to
make a screwdriver slot. You can also use the tiny diamond burr with
th dremel to make a "dent" atop the broken bolt for the drill bit to
start on when you drill it out.

Yes, I used the Dremel tool with a diamond grind bit to form a slot on
top of one of the broken bolt, and I used a screw driver to remove that
bolt -- successfully.

But this didn't work for another two bolts that were sunk inside the
holes. The pointy grinding bit simply could not have a good angle of
attack on the bolt surface. What ended up happening was that the two
ends of the slot were slightly lower than the center of the slot and
this weakened the slot. When I used the screw driver to turn the bolt,
I ended up stripping the slot.

But this is kind of behind me now. As mentioned in my another reply, I
found an easy way to remove the broken bolts by simply removing the
water pump base, and this allowed the broken bolts to show up in the
open, and I used a channellock piler to remove the broken bolts.

Nice to talk with you.

Jay Chan

wrote in message
ps.com...
Clams Canino wrote:
I wanna know how you broke *three*.
I mean - after you broke one... didn't a clue rake at least try to hit
you
over the head about the rest of them?

Actually, I could have broken all four -- instead of merely three. I
must have come to my sense when I was bearing down on the 4th bolt.

I have a tendency to over-doing anything (such as running my knee to
the point that I needed to have a surgery done on my knee). And
tightening up the bolts too much is one of my tendency. That was the
reason why I bought a torque wrench hoping that using the torque wrench
will prevent me from over-torquing the bolts. Unfortunately, I mistook
60-inch-pounds with 60-feet-pounds, and I ended up over-torquing the
bolts by 12 times. And the fact that the torque wrench that I use is
quite big (designed more for higher torque such as for torquing the
propeller); therefore, I didn't get a good feel of the tension. I have
ordered a 1/4" torque wrench that is designed for lower torque (such as
60-inch-pounds); hopefully, this will prevent me from making a similar
mistake.

Jay Chan


Look at the bright side. You are going to have a very well stocked tool box
by the time you are finished with this project. :-)

Eisboch

"Don White" wrote in message
...
Gene Kearns wrote:
snip...

This is a *BIG* hot button for me, but this is endemic of no longer
teaching real Industrial Arts in our public schools. Higher education,
from mechanic programs, to engineering programs, to medical programs
all suffer from incoming students that have, in too many cases, never
even held a tool in their hands..... and in almost all cases, save
some rural areas, lack any real experience in using tools or in
dealing with the logic required of fixing everyday items that need
repair or adjustment.....
--

You got that right!
When my two sons were in jr high, they had to take homemaking courses half
the year and shop the other half. The pc crowd decided that the girls
whould have equal time hammering, cutting etc. while the boys learned
baking, etc.
I don't mind if the girls want to take shop, but don't force the boys
to be Suzy Homemaker unless they want to.

So you figure the women will be the kitchen slave. Not much more pathetic
than a guy who has to go to Burger King because he can not cook anything!

Call around to hardware stores and ask if they sell spiral screw
extractors.
Before you jump in the car, measure the diameter of the bolt shafts you
need
to remove. And, if you know the socket size that fits the heads, write
that
down too.

I tried that already. Either it didn't work or I went too easy on the
hammer. Anyway, it could not grab the bolt and could not spin the bolt
out. I attempted to drill one of the broken bolt away. But this
simply messed up the thread in one of the hole.

Hammer????????

Do you mean I am not supposed to use a hammer to work with the screw
extractor? I am under the impression that I am supposed to drill a
hole in the middle of the borken bolt, and hammer the screw extractor
down into the hole, and then use some kind of handle bar to lock on the
screw extractor and turn counter clockwise, and hopefully the screw
will back out. This was exactly what the owner of the hardware store
told me to do.

May be we are talking about two different types of screw extractors?
May be you are referring to the type that is like a drill bit, and we
are supposed to use it with a power drill (running in reverse) to dill
and back off the bolt? I could not use that type because the bolt was
sunken inside a small hole that the special drill bit was too large to
fit inside.

Jay Chan