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

I'm rebuilding a Super Cub wing and the flanges on the ribs and the
spar caps have been drilled perfectly so the #4 steel screws go right
in, that is, if a screw has not been broken off. In which case I have
the option of redrilling and turning the spars into Swiss cheese and
losing ac43-13 edge distance on the rib flanges, or drilling out the
broken, embedded screws. Trouble is that when I try to drill the damn
broken screws out they harden and the drill bit becomes useless.

Looks like I need a #45 drill bit made of diamond or carbide. Ideas?
Thanks.

jls wrote:
I'm rebuilding a Super Cub wing and the flanges on the ribs and the
spar caps have been drilled perfectly so the #4 steel screws go right
in, that is, if a screw has not been broken off. In which case I have
the option of redrilling and turning the spars into Swiss cheese and
losing ac43-13 edge distance on the rib flanges, or drilling out the
broken, embedded screws. Trouble is that when I try to drill the damn
broken screws out they harden and the drill bit becomes useless.

Looks like I need a #45 drill bit made of diamond or carbide. Ideas?
Thanks.

I have a set of silicon carbide tipped drills. The guy
I bought them from used to go around to woodworking
shows demoing them by drilling holes in files and bricks,
glass blocks, all sorts of things, all with the same bit.

Yes, silicon carbide, not tungsten carbide.

Altavista has lots of hits on "diamond drill bit'".

But a #4 screw is tiny. Good Luck.

--

FF

wrote:
jls wrote:
I'm rebuilding a Super Cub wing and the flanges on the ribs and the
spar caps have been drilled perfectly so the #4 steel screws go right
in, that is, if a screw has not been broken off. In which case I have
the option of redrilling and turning the spars into Swiss cheese and
losing ac43-13 edge distance on the rib flanges, or drilling out the
broken, embedded screws. Trouble is that when I try to drill the damn
broken screws out they harden and the drill bit becomes useless.

Looks like I need a #45 drill bit made of diamond or carbide. Ideas?
Thanks.

I have a set of silicon carbide tipped drills. The guy
I bought them from used to go around to woodworking
shows demoing them by drilling holes in files and bricks,
glass blocks, all sorts of things, all with the same bit.

Yes, silicon carbide, not tungsten carbide.

Altavista has lots of hits on "diamond drill bit'".

But a #4 screw is tiny. Good Luck.

--

FF

Thanks, Fred. All these ribs I bought from Northland in Dakota
Territory @ $50 apiece were already drilled for screw holes-- eight per
rib and two for each nose rib. They matched up perfectly to the holes
drilled in the spars when this aircraft was built at the factory in the
fifties, so when I began fastening new ribs to the old spars I began
finding holes that were stopped up, i. e., holes where screws had been
broken off.

So a guy in the Supercub Club from the Cleveland area has advised me to
buy a pencil die grinder, i. e., a carbide tipped tool--- like the
dentists use--- to drill out the embedded screws.

Thanks for your very informative post.

jls wrote:
wrote:
jls wrote:
I'm rebuilding a Super Cub wing and the flanges on the ribs and the
spar caps have been drilled perfectly so the #4 steel screws go right
in, that is, if a screw has not been broken off. In which case I have
the option of redrilling and turning the spars into Swiss cheese and
losing ac43-13 edge distance on the rib flanges, or drilling out the
broken, embedded screws. Trouble is that when I try to drill the damn
broken screws out they harden and the drill bit becomes useless.

Looks like I need a #45 drill bit made of diamond or carbide. Ideas?
Thanks.

I have a set of silicon carbide tipped drills. The guy
I bought them from used to go around to woodworking
shows demoing them by drilling holes in files and bricks,
glass blocks, all sorts of things, all with the same bit.

Yes, silicon carbide, not tungsten carbide.

Altavista has lots of hits on "diamond drill bit'".

But a #4 screw is tiny. Good Luck.

--

FF

Thanks, Fred. All these ribs I bought from Northland in Dakota
Territory @ $50 apiece were already drilled for screw holes-- eight per
rib and two for each nose rib. They matched up perfectly to the holes
drilled in the spars when this aircraft was built at the factory in the
fifties, so when I began fastening new ribs to the old spars I began
finding holes that were stopped up, i. e., holes where screws had been
broken off.

So a guy in the Supercub Club from the Cleveland area has advised me to
buy a pencil die grinder, i. e., a carbide tipped tool--- like the
dentists use--- to drill out the embedded screws.

Thanks for your very informative post.

If you live close by to Greenbelt, MD or can wait until the next time
I'm in Cleveland, I'll lend my bits to you if you want to try them out.

Also, there are diamond bits available for the dremel tool.

--

FF

wrote:
jls wrote:
[...]
If you live close by to Greenbelt, MD or can wait until the next time
I'm in Cleveland, I'll lend my bits to you if you want to try them out.

Also, there are diamond bits available for the dremel tool.

--

FF

Well, Fred, I'm in Western North Carolina, but if you could tell me
where to purchase those silicon carbide bits, I'd buy some. Sounds
like all of us need some. I get tired of breaking bits all the time
and tossing away the dull ones. They ought to all be made out of
carbide or be diamond-tipped, unless you're drilling wood or soft
aluminum.

Thanks.

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?


jls wrote:
wrote:
jls wrote:
I'm rebuilding a Super Cub wing and the flanges on the ribs and the
spar caps have been drilled perfectly so the #4 steel screws go right
in, that is, if a screw has not been broken off. In which case I have
the option of redrilling and turning the spars into Swiss cheese and
losing ac43-13 edge distance on the rib flanges, or drilling out the
broken, embedded screws. Trouble is that when I try to drill the damn
broken screws out they harden and the drill bit becomes useless.

Looks like I need a #45 drill bit made of diamond or carbide. Ideas?
Thanks.

I have a set of silicon carbide tipped drills. The guy
I bought them from used to go around to woodworking
shows demoing them by drilling holes in files and bricks,
glass blocks, all sorts of things, all with the same bit.

Yes, silicon carbide, not tungsten carbide.

Altavista has lots of hits on "diamond drill bit'".

But a #4 screw is tiny. Good Luck.

--

FF

Thanks, Fred. All these ribs I bought from Northland in Dakota
Territory @ $50 apiece were already drilled for screw holes-- eight per
rib and two for each nose rib. They matched up perfectly to the holes
drilled in the spars when this aircraft was built at the factory in the
fifties, so when I began fastening new ribs to the old spars I began
finding holes that were stopped up, i. e., holes where screws had been
broken off.

So a guy in the Supercub Club from the Cleveland area has advised me to
buy a pencil die grinder, i. e., a carbide tipped tool--- like the
dentists use--- to drill out the embedded screws.

Thanks for your very informative post.

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.

Correction. Those ribs are Dakota Cub ribs from Dakota Territory, and
I bought a great set of struts and rudder from Northland in Alaska.
Great prices on shipping too, because of all the airplanes coming out
of Alaska almost empty, but going up full.

Thanks to Bud for the info on the Craftsman easy-outs.

I'm out here on an airport in the mtns. using a laptop and wireless
(and freezing) and it's the most beautiful place in the world. Don't
you think an airport at night with all those lights is prettier'n a
Christmas tree?