Often I need to extract broken bolts / screws and am thinking about
picking up some left handed drill bits. Usually I have to extract
broken steel bolts and screws from aluminum heads and manifolds. Most
often they are broke off clean and need to be drilled. When looking at
drill bits to purchase, I see they are made of HSS, Cobalt and
Titanium. What drill bit material is the best for staying sharp and
long lasting life?
Also, please comment on grabit and other extracting methods. What do
you think is the easiest way to remove a broken bolt?
Thanks for any advice
My favorite method is to center up an oversize hex nut (3/8
nut on a 1/4 bolt etc.) over
the broken remains, use a mig welder to weld the nut to the
Give it a shot of Kroil and unscrew. For small stuff drill
a hole in some sheet metal,
weld it to the screw, and weld a hex nut to the sheet metal.
Lots of Kroil, maybe run
it through a couple of heat/cool cycles, be patient. Works
90% + of the time.
Last time I tried that I found that the busted bolts I had to remove
were unhardened, and of some alloy that my MIG welder wouldn't penetrate
it worth a damn! let that be a lesson to you, always use Grade 5!
replace "roosters" with "cox" to reply.
Any tool for extraction will work but it's the setup that counts.
For the highest success rate it is beset to follow this procedure,
especially when removing a hard bolt from a softer surrounding
material like aluminum.
1. If broken bolt is above surface grab it with vise grips, use a
engraving tool to buzz it out, or turn it with a sharp punch.
2. If this doesn't work grind the surface perpendicular to the
3. With a magnifying glass if you need one, punch the
exact center of the bolt. Re-punch if you are off a bit.
4. Take a small drill and carefully without breaking the bit, drill
a pilot hole.
5. Step up to a larger drill that you feel you will not break
and adjust the drill location if necessary to make the
hole exactly in the center. Drill all the way through the
bolt if possible.
6. Now pick the correct size left hand drill, or drill/EZ out
If the bolt is bellow surface and uneven use steps three through
six. Pay great attention to step three, four and five.
It takes the place of a punch. Orient the engraver so
that it pushes the perimeter, or whatever is available in a
counterclockwise direction. This will only work if the bolt is
not completely seized but just inaccessible.
I have used one of those automatic punches chucked up to a drill press that
is not spinning. Easy down until you get it right and clamped. If I try by
hand, it seems to run off. If surface is slanted, you can also place shims
under the clamp to flatten out the angle so the hole happens pretty close to
I have found that hitting the stub with a hammer, with or without a punch,
as hard and as much as possible without destroying it often helps a great
deal in freeing the bolt from the corrosion which locks it tight. If you can
be lucky enough to drill the stub not quite all the way through, you can
insert a punch into the hole and stretch the bottom of the stub. This will
nearly always free it.
This is (I think) the kind of engraving tool which has a carbide
point in an adjustable vibrator Something like a "Burgess Vibro-Graver".
You place the point on an area away from the center of the broken bolt,
but not too close to the threads, and angle it so is is driving both
down into the bolt and CCW. This is likely to get the bolt out --
though to be honest, I've never tried it.
I'll have to remember to try that next time I have that
Enjoy -- and now "Happy New Year",
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I have had several bolts break off flush, and could still be turned with
just the point of an ice pick, or one of those little dental tools. A
"buzzer" would impart a little force on there. Putting penetrant on there
and leaving it sit surely wouldn't hurt. Critical points is that the
threads are not boogered up, and that you put the point on the broken piece
and keep it towards the center away from the threads. A lot of times, the
break leaves a slight "shoulder" that the point can be pushed against.
Yup, I've done that many times, usually using a piece of hardened steel
shaft (actually often a broken "knockout pin" from a cold heading
machine, because that was the type of machinery I was working on) ground
to a fine point on a bench grinder and a 3 lb. hammer. A nail might
work in a pinch although you'll undoubtedly ruin it - the modified
knockout punch was reusable, so I only had to make one every couple
months or so. That only works on bolts that have broken due to fatigue
or overtightening though, not ones that snapped when loosening due to
threads being seized.
replace "roosters" with "cox" to reply.
In that case, what's the point of the vise grips?
This suggestion needs more explanation to make any sense to me -- if the
bolt is so bound as to have caused it to twist off in place, seems
unlikely this is going to work -- although I've no such engraving tool,
I'm the heat cycle kinda' guy, meself... :)
I do like the idea of the tack-weld a new nut on -- now if I only had a
MIG or wire-feed unit instead of (or in addition to) the stick... :)
Sometimes a bolt head will shear off because of sideways forces, and not be
in the threads hard. Sometimes there is not enough sticking up to get a
vise grip on there. I have had several that once you got it turned a couple
of turns with an ice pick, you could get it the rest of the way out with
They're all different.
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