How to extract stuck screw
Ray Yokoyama & Danelle Cox
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Imagine this: You're doing the first tune-up on your newly acquired
bike. To get the oil filter cover off you need to remove three
cross-head screws. You apply your trusty $1.89 K-Mart screwdriver to the
first screw, and turn. The screwdriver slips out, so
you try again, pushing harder. It slips out again, rounding the screw
head a little. But you've got your trusty Vice-Grips in the
tool box, so you clamp them onto the screwdriver's shank and really bear
down on the screwdriver... this time stripping the
head completely. Arrrgh!
If you've worked on bikes at all you're probably nodding your head right
about now, saying "yeah, I did something like that."
Bikes today have higher-quality fasteners than they did 10 or 20 years
ago, but still the various forces of entropy conspire to
stick fasteners together a little stronger than they're designed for.
Here's a guide to un-sticking stuck fasteners.
Impact Driver
The best remedy for a stuck screw, or one whose head has been stripped,
is the impact screwdriver. An impact screwdriver is essentially two
weights held apart by a spring. The bottom one holds screwdriver bits.
You smack the top one with a hammer. In between them is a spring and a
circular ramp. The ramp makes the bottom weight with the bit in it turn.
So when you hit the top weight, giving it momentum, it compresses the
spring and hits the ramp which turns the screwdriver-bit-holding bottom
weight. The beauty of the design is that the force you impart to the
impact wrench by hitting it with the hammer
is forced into the screw, helping the screwdriver bit bite into the
screw head (or what's left of it). Most impact drivers will let you set
them for left and right turning, to loosen or tighten screws.
The high-quality, hardened screwdriver bits that come with impact
drivers usually fit the screw heads much better than even the
best screwdrivers, which helps all by itself. So at the first sign of a
recalcitrant Phillips head screw, reach for the impact driver!
Impact drivers are commonly available and cost about 15 (American)
dollars - check your local auto supply store.
Some cheap impact drivers have (relatively) stiff springs which require
a heavy hammer to compress and get the ramps to turn
the bit. Be warned that the force needed may be damaging to the assembly
in which the screw is stuck, or may be difficult to
counteract on an awkward piece. These impact drivers can benefit from
being disassembled and having the springs shortened
slightly (no more than 25 percent) to reduce the spring preload. After
this modification the driver will not require as much force
but may not work quite as well on really badly buggered screws.
Screw Extractor
When an impact driver can't remove a screw, or there's not enough of the
screw protruding to grip, the next step is to drill off the screw's head
and then use a screw extractor. A screw extractor is a very hard
reverse-thread bit. You drill a hole into the
screw, then carefully tap the proper extractor (which has a smaller
initial diameter than the hole, and quickly flares out) into the hole,
and use it to twist out what is left of the screw. The reverse flutes on
the extractor cause it to bite harder into the metal of the screw as you
put more force on it. Screw extractor bits are made of very hard metal,
so they are very brittle. It is very easy to break one off inside the
screw. When that happens you are screwed (sorry for the pun)- the
extractor metal is harder than any drill bit, so you can't drill it out.
The only recourse will be EDM (see below). To turn the extractor you
should use a tap handle commonly used to turn threading taps. The screw
extractor has a square end to fit into the tap handle. Using a regular
wrench to turn the extractor is almost guaranteed to break it.
You should be very careful when drilling the hole in the screw.
Obviously you don't want to drill into the material surrounding the
screw, so be careful to line up the drill in the center of the screw.
Use a drill press if you have one and the part is small enough that you
can set it up solidly in the press. Drill slowly and stop often to check
your progress. Drill a small pilot-hole first, using a punch to mark the
spot before you start drilling.
Many times, drilling the hole in the screw will be enough to loosen it
as the pressure is released, and you will be able to ease it out with
little force on the extractor.
Drilling out screws
If that doesn't work, the next option, depending on the design of the
cover that the screw holds down, is to drill out the screw head
completely. Often times, removing the head of the screw releases the
pressure of holding two parts together, and again will come out easily,
unless of course it is rusted or frozen. In this case, if there is
enough of the screw-shank sticking out after the cover's removed to let
you file flats on it, use locking pliers to turn it.
Use a drill bit that is just large enough to take out the screw's head;
it should be slightly larger than the shank of the screw so
that when you drill through the head and get to the shank the head will
come completely off. Obviously you need to have the
hole exactly centered to do this without touching the surrounding
material. If the buggered screw head is irregular this is difficult
to do with a hand-held drill, as the drill will catch on the protruding
bits and go off-center. You may be able to even out the
screw head with a small file or a pointed grinding-stone in a
dremel-tool (small high-speed hand-held grinder) then
center-punch and drill.
Other Methods
Sometimes you can grasp the head of a screw with a pair of locking
pliers and use their better grip to get enough torque on it to
get it started. Or you can carefully file flats in what's left of the
head, or on the threaded portion itself if it protrudes.T his
obviously will require that the screw be replaced after it's removed,
but it can help you to get it out so it can be replaced.
A couple of tricks for short screws: you can heat the screw with a
torch. Often heating and cooling threads loosens them. If the
screw is held in with a locking agent (e.g."LockTite") heat will destroy
the bond and make it easier to remove. You need to be
able to heat the threaded part of the screw; long screws with their
threads deep inside the engine cases will not be affected by
heating the screw head. Don't use anything stronger than a propane
torch; an oxy-acetylene torch can burn through a set of
aluminum cases in short order. Even with a propane torch, don't hold the
torch on one section of the cases for more than a
second, play it around a small area near the screw. Don't heat the cases
too hot; hot enough to sizzle when a drop of water is
put on them is hot enough.
A second trick is to use a dremel-tool to grind a flat on the periphery
of the screw head, and then use a hammer and punch on
the flat to turn the screw. This works on the tiny short screws
sometimes used to hold gear box bearings into crank cases.
Stuck Nuts and Bolts
Bolts get stuck just like screws do, the difference is that bolt heads
are usually sturdier so rounding off the head is not so much
of a problem. If you do round off a bolt head the methods to remove it
are similar to the ones used to remove screws.
However the usual problem is that you just can't turn the bolt. The
first thing to try is more leverage. If you're using a sturdy
breaker-bar for sockets you can slip a length of water pipe over it to
use as a cheater bar. A regular ratchet handle isn't up to
the stress that you can generate this way. For nuts and bolts over 13mm
you should use a 1/2" drive bar.
With a long cheater bar the limit to how much force you can apply is
determined by what it takes to move the entire assembly.
For instance to remove the rotor nut from an RZ350 crankshaft, a four
foot cheater bar is required. If the engine is out of the
bike you will need to strap it to your workbench and get a friend to
help hold it and the workbench in place.
Impact Wrench
An alternative to cheater bars is an impact wrench. These are available
in both air-driven and electric models. The air-driven
type is what the local car tire shop uses to remove car wheels. Impact
wrenches work by using air or an electric motor to turn a
rotating weight which slams repeatedly into a lever connected to the
socket drive. Since they hammer the socket drive around a
small step at a time, there is very little torque reaction, so it
doesn't take much effort to prevent the shaft that the nut or bolt is
attached to from turning. Most 1/2 inch drive impact wrenches can
deliver 75 ft-lbs of torque or more. Air impact wrenches
cost from 35 dollars up and require an air compressor. Electric impact
wrenches cost more, they start at 80 dollars, but do not
require air. They're useful for racers who compete at tracks with
electrical outlets in the pit area.
One caution, an impact wrench shouldn't be used to tighten nuts or bolts
on motorcycles (except perhaps those RZ350 rotor
nuts) as their torque settings, if they exist at all, are very
approximate. It's easy to over-tighten a nut or bolt with an impact
wrench.
Desperate Measures
Another way to remove stuck nuts is to use a nut splitter. It's not as
painful as it sounds. A nut splitter is a steel collar which
slips around the nut. One side of the collar has a hard steel wedge
which is driven into the nut to split it by turning a bolt on the
side of the collar. These are only needed to remove really badly rusted
nuts, usually on the under carriage of cars. Their use on
motorcycles is rare, but if you have a nut that's hopeless and can't be
removed any other way you should be aware that this tool
exists.
Another option is a small cutting wheel in a dremel-tool. It will spray
hot sparks and bits of grit all over, and will generate a lot
of heat, but it can cut through the ugliest frozen nut... if you can get
to it. If it's buried deep inside aluminum cases, there's one
last possibility: EDM.
EDM
The Option of Last Resort is Electrical-Discharge Machining. EDM can be
used to electrically machine a hopelessly stuck steel
bolt or screw out of aluminum cases or heads. The equipment is not
generally available in the home workshop; you will need to
take the entire assembly to a shop that does EDM. Certain hard-core home
shop fanatics have constructed home EDM
machines of varying capacities, and plans for them do exist, but given
the infrequent usage for motorcycle mechanics it is more
economical to farm out the work.
EDM, also called spark erosion, uses an electric spark to remove metal.
An electrode is moved close to the work piece and
sparks are repeatedly struck between the two. The gap has to be
controlled very closely, so EDM machines are electrically
controlled. EDM can machine to fine tolerances, but the closer the
tolerance, the slower the machining.
EDM is becoming more popular and available. If you've broken off a stud
inside your cases, it might cost 50 dollars to get
someone to use EDM to remove it. You will probably need to drill out the
remains of the stud and use a thread insert ("heli
coil") in that hole, but if it saves a 500-dollar set of crank cases
you're still way ahead.
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<HTML>
Imagine this: You're doing the first tune-up on your newly acquired bike.
To get the oil filter cover off you need to remove three
<BR>cross-head screws. You apply your trusty $1.89 K-Mart screwdriver to
the first screw, and turn. The screwdriver slips out, so
<BR>you try again, pushing harder. It slips out again, rounding the screw
head a little. But you've got your trusty Vice-Grips in the
<BR>tool box, so you clamp them onto the screwdriver's shank and really
bear down on the screwdriver... this time stripping the
<BR>head completely. Arrrgh!
<P>If you've worked on bikes at all you're probably nodding your head right
about now, saying "yeah, I did something like that."
<BR>Bikes today have higher-quality fasteners than they did 10 or 20 years
ago, but still the various forces of entropy conspire to
<BR>stick fasteners together a little stronger than they're designed for.
Here's a guide to un-sticking stuck fasteners.
<P><B><U>Impact Driver</U></B>
<P>The best remedy for a stuck screw, or one whose head has been stripped,
is the impact screwdriver. An impact screwdriver is essentially two weights
held apart by a spring. The bottom one holds screwdriver bits. You smack
the top one with a hammer. In between them is a spring and a circular ramp.
The ramp makes the bottom weight with the bit in it turn. So when you hit
the top weight, giving it momentum, it compresses the spring and hits the
ramp which turns the screwdriver-bit-holding bottom weight. The beauty
of the design is that the force you impart to the impact wrench by hitting
it with the hammer
<BR>is forced into the screw, helping the screwdriver bit bite into the
screw head (or what's left of it). Most impact drivers will let you set
them for left and right turning, to loosen or tighten screws.
<P>The high-quality, hardened screwdriver bits that come with impact drivers
usually fit the screw heads much better than even the
<BR>best screwdrivers, which helps all by itself. So at the first sign
of a recalcitrant Phillips head screw, reach for the impact driver!
<BR>Impact drivers are commonly available and cost about 15 (American)
dollars - check your local auto supply store.
<P>Some cheap impact drivers have (relatively) stiff springs which require
a heavy hammer to compress and get the ramps to turn
<BR>the bit. Be warned that the force needed may be damaging to the assembly
in which the screw is stuck, or may be difficult to
<BR>counteract on an awkward piece. These impact drivers can benefit from
being disassembled and having the springs shortened
<BR>slightly (no more than 25 percent) to reduce the spring preload. After
this modification the driver will not require as much force
<BR>but may not work quite as well on really badly buggered screws.
<P><B><U>Screw Extractor</U></B>
<P>When an impact driver can't remove a screw, or there's not enough of
the screw protruding to grip, the next step is to drill off the screw's
head and then use a screw extractor. A screw extractor is a very
hard reverse-thread bit. You drill a hole into the
<BR>screw, then carefully tap the proper extractor (which has a smaller
initial diameter than the hole, and quickly flares out) into the hole,
and use it to twist out what is left of the screw. The reverse flutes on
the extractor cause it to bite harder into the metal of the screw as you
put more force on it. Screw extractor bits are made of very hard metal,
so they are very brittle. It is very easy to break one off inside the screw.
When that happens you are screwed (sorry for the pun)- the extractor metal
is harder than any drill bit, so you can't drill it out. The only recourse
will be EDM (see below). To turn the extractor you should use a tap handle
commonly used to turn threading taps. The screw extractor has a square
end to fit into the tap handle. Using a regular wrench to turn the extractor
is almost guaranteed to break it.
<P>You should be very careful when drilling the hole in the screw. Obviously
you don't want to drill into the material surrounding the screw, so be
careful to line up the drill in the center of the screw. Use a drill press
if you have one and the part is small enough that you can set it up solidly
in the press. Drill slowly and stop often to check your progress. Drill
a small pilot-hole first, using a punch to mark the spot before you start
drilling.
<P>Many times, drilling the hole in the screw will be enough to loosen
it as the pressure is released, and you will be able to ease it out with
little force on the extractor.
<P><U><B>Drilling out screws</B></U>
<P>If that doesn't work, the next option, depending on the design of the
cover that the screw holds down, is to drill out the screw head completely.
Often times, removing the head of the screw releases the pressure of holding
two parts together, and again will come out easily, unless of course it
is rusted or frozen. In this case, if there is enough of the screw-shank
sticking out after the cover's removed to let you file flats on it, use
locking pliers to turn it.
<P>Use a drill bit that is just large enough to take out the screw's head;
it should be slightly larger than the shank of the screw so
<BR>that when you drill through the head and get to the shank the head
will come completely off. Obviously you need to have the
<BR>hole exactly centered to do this without touching the surrounding material.
If the buggered screw head is irregular this is difficult
<BR>to do with a hand-held drill, as the drill will catch on the protruding
bits and go off-center. You may be able to even out the
<BR>screw head with a small file or a pointed grinding-stone in a dremel-tool
(small high-speed hand-held grinder) then
<BR>center-punch and drill.
<P><B><U>Other Methods</U></B>
<P>Sometimes you can grasp the head of a screw with a pair of locking pliers
and use their better grip to get enough torque on it to
<BR>get it started. Or you can carefully file flats in what's left of the
head, or on the threaded portion itself if it protrudes.T his
<BR>obviously will require that the screw be replaced after it's removed,
but it can help you to get it out so it can be replaced.
<P>A couple of tricks for short screws: you can heat the screw with a torch.
Often heating and cooling threads loosens them. If the
<BR>screw is held in with a locking agent (e.g."LockTite") heat will destroy
the bond and make it easier to remove. You need to be
<BR>able to heat the threaded part of the screw; long screws with their
threads deep inside the engine cases will not be affected by
<BR>heating the screw head. Don't use anything stronger than a propane
torch; an oxy-acetylene torch can burn through a set of
<BR>aluminum cases in short order. Even with a propane torch, don't hold
the torch on one section of the cases for more than a
<BR>second, play it around a small area near the screw. Don't heat the
cases too hot; hot enough to sizzle when a drop of water is
<BR>put on them is hot enough.
<P>A second trick is to use a dremel-tool to grind a flat on the periphery
of the screw head, and then use a hammer and punch on
<BR>the flat to turn the screw. This works on the tiny short screws sometimes
used to hold gear box bearings into crank cases.
<P><B><U>Stuck Nuts and Bolts</U></B>
<P>Bolts get stuck just like screws do, the difference is that bolt heads
are usually sturdier so rounding off the head is not so much
<BR>of a problem. If you do round off a bolt head the methods to remove
it are similar to the ones used to remove screws.
<P>However the usual problem is that you just can't turn the bolt. The
first thing to try is more leverage. If you're using a sturdy
<BR>breaker-bar for sockets you can slip a length of water pipe over it
to use as a cheater bar. A regular ratchet handle isn't up to
<BR>the stress that you can generate this way. For nuts and bolts over
13mm you should use a 1/2" drive bar.
<P>With a long cheater bar the limit to how much force you can apply is
determined by what it takes to move the entire assembly.
<BR>For instance to remove the rotor nut from an RZ350 crankshaft, a four
foot cheater bar is required. If the engine is out of the
<BR>bike you will need to strap it to your workbench and get a friend to
help hold it and the workbench in place.
<P><B><U>Impact Wrench</U></B>
<P>An alternative to cheater bars is an impact wrench. These are available
in both air-driven and electric models. The air-driven
<BR>type is what the local car tire shop uses to remove car wheels. Impact
wrenches work by using air or an electric motor to turn a
<BR>rotating weight which slams repeatedly into a lever connected to the
socket drive. Since they hammer the socket drive around a
<BR>small step at a time, there is very little torque reaction, so it doesn't
take much effort to prevent the shaft that the nut or bolt is
<BR>attached to from turning. Most 1/2 inch drive impact wrenches can deliver
75 ft-lbs of torque or more. Air impact wrenches
<BR>cost from 35 dollars up and require an air compressor. Electric impact
wrenches cost more, they start at 80 dollars, but do not
<BR>require air. They're useful for racers who compete at tracks with electrical
outlets in the pit area.
<P>One caution, an impact wrench shouldn't be used to tighten nuts or bolts
on motorcycles (except perhaps those RZ350 rotor
<BR>nuts) as their torque settings, if they exist at all, are very approximate.
It's easy to over-tighten a nut or bolt with an impact
<BR>wrench.
<P><B><U> Desperate Measures</U></B>
<P>Another way to remove stuck nuts is to use a nut splitter. It's not
as painful as it sounds. A nut splitter is a steel collar which
<BR>slips around the nut. One side of the collar has a hard steel wedge
which is driven into the nut to split it by turning a bolt on the
<BR>side of the collar. These are only needed to remove really badly rusted
nuts, usually on the under carriage of cars. Their use on
<BR>motorcycles is rare, but if you have a nut that's hopeless and can't
be removed any other way you should be aware that this tool
<BR>exists.
<P>Another option is a small cutting wheel in a dremel-tool. It will spray
hot sparks and bits of grit all over, and will generate a lot
<BR>of heat, but it can cut through the ugliest frozen nut... if you can
get to it. If it's buried deep inside aluminum cases, there's one
<BR>last possibility: EDM.
<P><B><U>EDM</U></B>
<P>The Option of Last Resort is Electrical-Discharge Machining. EDM can
be used to electrically machine a hopelessly stuck steel
<BR>bolt or screw out of aluminum cases or heads. The equipment is not
generally available in the home workshop; you will need to
<BR>take the entire assembly to a shop that does EDM. Certain hard-core
home shop fanatics have constructed home EDM
<BR>machines of varying capacities, and plans for them do exist, but given
the infrequent usage for motorcycle mechanics it is more
<BR>economical to farm out the work.
<P>EDM, also called spark erosion, uses an electric spark to remove metal.
An electrode is moved close to the work piece and
<BR>sparks are repeatedly struck between the two. The gap has to be controlled
very closely, so EDM machines are electrically
<BR>controlled. EDM can machine to fine tolerances, but the closer the
tolerance, the slower the machining.
<P>EDM is becoming more popular and available. If you've broken off a stud
inside your cases, it might cost 50 dollars to get
<BR>someone to use EDM to remove it. You will probably need to drill out
the remains of the stud and use a thread insert ("heli
<BR>coil") in that hole, but if it saves a 500-dollar set of crank cases
you're still way ahead.
<BR> </HTML>
--------------93F1C5C92B7CEA1A78E5B067--
-jc
It is good .... it's also word for word from and article at Motorcycle
Online. You can check it out at
http://www.motorcycle.com/mo/mcnuts/stuckscrews.html
Sheesh ....
--
- Jeff
- 93 CR500
- 96 ZX-9R
- Remove "*Spam_Free*" from my address to reply.
Patrick Riley wrote:
>
> This is very good. A possible candidate for the RMD FAQ.
>
> Ray Yokoyama & Danelle Cox wrote:
> >
> > Imagine this: You're doing the first tune-up on your newly acquired
> > bike. To get the oil filter cover off you need to remove three
> > cross-head screws. You apply your trusty $1.89 K-Mart screwdriver to
> > the first screw, and turn. The screwdriver slips out, so
> > you try again, pushing harder. It slips out again, rounding the screw
> > head a little. But you've got your trusty Vice-Grips in the
> > tool box, so you clamp them onto the screwdriver's shank and really
> > bear down on the screwdriver... this time stripping the
> > head completely. Arrrgh!
> >
snip
dustyboots
Ray Yokoyama & Danelle Cox wrote:
[Snip]
> Here's a guide to un-sticking stuck fasteners.
>
> Impact Driver
>
[Snip great post]
Great summary of tools and techniques! The info on EDM was a new for
me; I'll pack that away in the brain webs for future recall.
Jim Hall
Ray Yokoyama & Danelle Cox <digi...@gte.net> wrote:
>Here's a guide to un-sticking stuck fasteners.
>
Good post! but I would like to add one thing:
Cold chisel. (small and sharp).
This often works on screws that fail the impact driver method, also on
bolts that have had the head torqued off.
The trick is to dig the corner of the chisel into the outside of the
bolt. Then tap around in a (usually) counterclockwise direction to
remove the bolt.
I first saw this done a long time ago by an old mechanic on a snapped
off 6mm exhaust stud. It was frozen into the head and snapped off
flush under the double nut removal method.
When he told me what he was going to do, I said "no way". It took
him about 30 seconds to have the stud out. Since then, I have amazed
quite a few folks with this trick. I'm not sure that I have ever had
it fail, provided I had enough access to the bolt to whack it in the
right direction.
Sounds hokey, but I would definately recommend it before I got out the
drill and "easy" outs. It's one of the best tricks I've got.
--
When the going gets Weird - the weird turn Pro....
h.s.thompson
Jim Hall
Flagstaff, AZ
REPLY TO: jdh...@plateau.com
83 IT465
94 KDX250
Ray Yokoyama & Danelle Cox
Thanks for the tip. I'll have to try that one day.
Jim Hall wrote:
> Ray Yokoyama & Danelle Cox <digi...@gte.net> wrote:
>
> >Here's a guide to un-sticking stuck fasteners.
> >
>
DJones7454
In article <64d770$j9h$1...@heap.juniper.net>, -jc
<campbell@*Spam_Free*juniper.net> writes:
>It is good .... it's also word for word from and article at Motorcycle
>Online. You can check it out at
>http://www.motorcycle.com/mo/mcnuts/stuckscrews.html
>
>Sheesh ....
>
>--
>- Jeff
Seems like the one who posted the article should at least let us know from
where he stole it! Don't get me wrong, I am not against "borrowing" some
information but let us know it isn't really you *talking*, but
copying......makes ya look too smart....;-)
DJ
DirtCrashr
>It is good .... it's also word for word from and article at Motorcycle
>Online. You can check it out at
>http://www.motorcycle.com/mo/mcnuts/stuckscrews.html
>
>Sheesh ....
>
>--
>- Jeff
Good catch Jeff!
DirtCrashr - '97xr400
DirtCrashr
>> Good catch Jeff!
>>
>> DirtCrashr - '97xr400
>
>deal, if he/she would give proper credit to the author and publisher.
>
>- Jeff
>- 93 CR500
I know if it was pictures that I had shot and someone else was taking de-facto
credit for them, I'd be really pissed off. That's basic copyright
infringement any way you look at it -- there should be credit given to the
author(s).
DirtIndignant - '97xr400