aluminum rib, aluminum spar, holes drilled but screws broken off

wright1902glider wrote:
You might also try a left-hand (that is the reverse of standard,
right?) drill bit. HF sells 'em, and you may also find them packaged
with a set of EZ-outs at the BLUE or ORANGE stores. That might work if
the screws aren't corroded into the holes. If there's enough of a screw
left, I've also had mixed results filing flats on the screws 180
degrees opposed, and grabbing on with a crescent wrench or vice-grips.
Careful, don't break the screw off a second time like I did.

You might also try drilling with cutting fluid. I had a similar
experience trying to drill out a set of rivets holding the ball joints
into my Dodge. (Wadda they make those damn rivets out of anyway?) With
the hand-electric drill it took 27 broken bits and 4 days. When I did
the other side, I pulled the a-arm out of the truck, mounted in a vise
on the drill press, and then drilled down using a 1/64" cobalt bit and
cutting fluid. It only took about 5 minutes per hole using 7 different
sized bits to achieve the same results. I wasn't using any more
pressure or speed with the drill press. So maybe the cutting fluid is a
semi-magic bullet?



Excellent advice, there Wright 1902. Thanks a lot. I'll run to the
HF store and see what I can find. Something's gotta work.

Sears has a nice set of extractors called "Power Extractors" that go
down to #40 size. In the small sizes, they have a left hand drill on
one end, and a fluted extractor on the other. I have used them to
remove many a broken and stuck screw on my plane and they work well.
The product # is 00952155000 on the Sears website. Also this webpage
has it.

http://www.sears.com/sr/javasr/produ...seBVCookie=Yes

Most Sears stores I have looked in have them.

Regards,
Bud

jls wrote:
wright1902glider wrote:
You might also try a left-hand (that is the reverse of standard,
right?) drill bit. HF sells 'em, and you may also find them packaged
with a set of EZ-outs at the BLUE or ORANGE stores. That might work if
the screws aren't corroded into the holes. If there's enough of a screw
left, I've also had mixed results filing flats on the screws 180
degrees opposed, and grabbing on with a crescent wrench or vice-grips.
Careful, don't break the screw off a second time like I did.

You might also try drilling with cutting fluid. I had a similar
experience trying to drill out a set of rivets holding the ball joints
into my Dodge. (Wadda they make those damn rivets out of anyway?) With
the hand-electric drill it took 27 broken bits and 4 days. When I did
the other side, I pulled the a-arm out of the truck, mounted in a vise
on the drill press, and then drilled down using a 1/64" cobalt bit and
cutting fluid. It only took about 5 minutes per hole using 7 different
sized bits to achieve the same results. I wasn't using any more
pressure or speed with the drill press. So maybe the cutting fluid is a
semi-magic bullet?



Excellent advice, there Wright 1902. Thanks a lot. I'll run to the
HF store and see what I can find. Something's gotta work.

Lots of good advice given but there's one problem that hasn't been
addressed. That's keeping the drill bit in the broken screw and not
letting it wander off into the spar. if the screw has been broken off
under flush there's not an easy way of dressing up the surface for a
good start. To keep from really messing up the job you may want to make
a drill guide to keep the bit aligned and going straight into the
broken screw.
A piece of 1/2" square steel stock about 8" long from any hardware
store will do. Set it up in a drill ress and drill a hole the size of
the bit you want to use through one side directly through. Set the bar
on the spar and line up the hole over the broken screw and then clamp
the bar down securely to the spar flange. Now you can drill through the
bar into the broken screw with far less chance of needing one of those
special figure eight shaped screws to cover the mess you made.
Any good quality SHARP drill bit will do the job with the correct
technique. For drilling out steel screws, use a slower RPM and more
pressure than for drilling aluminum. Start with a couple of light taps
at high RPM to ensure the drill gets a good center on the broken screw
shank or use a small center punch that will fit through the guide.
Using cutting oil is a good idea.
I don't think the Craftsman extractors are small enough for a #4
screw. I would go with a left handed bit, mouse milk, and take my time.

On 2 Jan 2007 03:34:14 -0800, "Charles" wrote:



Lots of good advice given but there's one problem that hasn't been
addressed. That's keeping the drill bit in the broken screw and not
letting it wander off into the spar. if the screw has been broken off
under flush there's not an easy way of dressing up the surface for a
good start. To keep from really messing up the job you may want to make
a drill guide to keep the bit aligned and going straight into the
broken screw.
A piece of 1/2" square steel stock about 8" long from any hardware
store will do. Set it up in a drill ress and drill a hole the size of
the bit you want to use through one side directly through. Set the bar
on the spar and line up the hole over the broken screw and then clamp
the bar down securely to the spar flange. Now you can drill through the

I would suggest using a "center drill" that just nicely fits the hole
in the steel plate at this point. It won't wander and will create a
nice cone shaped indentation in the screw shank.

Then switch to a drill and metal plate with a hole that fits the
drill. A good sharp drill *should*follow the screw

bar into the broken screw with far less chance of needing one of those
special figure eight shaped screws to cover the mess you made.
Any good quality SHARP drill bit will do the job with the correct
technique. For drilling out steel screws, use a slower RPM and more
pressure than for drilling aluminum. Start with a couple of light taps
at high RPM to ensure the drill gets a good center on the broken screw
shank or use a small center punch that will fit through the guide.
Using cutting oil is a good idea.
I don't think the Craftsman extractors are small enough for a #4
screw. I would go with a left handed bit, mouse milk, and take my time.
Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com

I just looked, and the Craftsman extractors I referenced go down to a #
5 screw. It had a reference for a size smaller than #6, and I thought
it was a #4, but alas.

Bud


Charles wrote:
Lots of good advice given but there's one problem that hasn't been
addressed. That's keeping the drill bit in the broken screw and not
letting it wander off into the spar. if the screw has been broken off
under flush there's not an easy way of dressing up the surface for a
good start. To keep from really messing up the job you may want to make
a drill guide to keep the bit aligned and going straight into the
broken screw.
A piece of 1/2" square steel stock about 8" long from any hardware
store will do. Set it up in a drill ress and drill a hole the size of
the bit you want to use through one side directly through. Set the bar
on the spar and line up the hole over the broken screw and then clamp
the bar down securely to the spar flange. Now you can drill through the
bar into the broken screw with far less chance of needing one of those
special figure eight shaped screws to cover the mess you made.
Any good quality SHARP drill bit will do the job with the correct
technique. For drilling out steel screws, use a slower RPM and more
pressure than for drilling aluminum. Start with a couple of light taps
at high RPM to ensure the drill gets a good center on the broken screw
shank or use a small center punch that will fit through the guide.
Using cutting oil is a good idea.
I don't think the Craftsman extractors are small enough for a #4
screw. I would go with a left handed bit, mouse milk, and take my time.