Broken #4 Rib Attachment Screws Embedded in Spar Cap

[James L. Smith]

Any way to get these out without enlarging the holes? Or, even enlarging the hole is better than having to re-drill beside the embedded screw. I have eight of these little pests to deal with.

I've tried drilling them out. The bit just dulls as the steel work-hardens, and you get nowhere. You don't have much room on the rib flange to redrill to satisfy edge distance requirements, and you certainly don't have any up-or-down movement on the spar cap flange.

Tried to find a carbide-tipped bit --- none that small. It's got to be a #40 bit.

What do +YOU+ do when faced with this utterly earth-shaking problem?

Thanks.

 

[behindpropellers]

I have a pencil die grinder for that kind of stuff. Sme type of tool the dentist uses.

Tim

 

[Crash]

delete

 

[Snert]

I have a set of left hand drill bits that I use for problems like this.

 

[jk]

or die grinder or dremel with a cut off wheel attached. Cut a slot in the head and remove with a slotted scewdriver.

 

[d.grimm]

I second Snert's advice. Left hand drill bits are the way to go.

 

[bat443]

You might try getting a cobalt drill bit from an industrial supply or non cut rate chain auto supply ( those old local auto parts have many more choices and usually sales people who work on projects). I even think Aircraft Spruce has them. The aviation tool suppliers list them in their catalogs also, check Trade-A-Plane and give them a call. Industrial supplies also often times have solid carbide drills in small size, though expensive compared to high speed steel. Tim

 

[jrussl]

I don't do a lot of "official" wrenching on airplanes but am very familiar with metal working. The advice on drilling above is dead on. Drilling technique is everything. The main thing is to keep the bit cool and keep it making a chip all the time. If the bit slips/rubs without pulling a chip, more heat is generated and you stand a good chance of work hardening the material you are drilling. Stainless is especially prone to this. Use a slow speed and keep firm constant pressure on the bit. Don't even start to drill unless you have firm pressure on it.

Carbide is always a good alternative if all else fails. Here's a source for a solid carbide #40 drill bit. I posted an image as I couldn't figure out how to get a link into the catalog.

Jeff

 

[tempdoug]

Call Mark at Dakota Cub, because when thats all you do for a living is put screws into wings, im sure hes been through some trying times with those #4s. doug

 

[coxcub]

I have one to remove where a #4 rib brace meets the spar that has sheared flush with the spar cap flange - how do people get the drill started on centre without it skating all over the place? or do I redrill the spar and change the angle of the brace. If that is possible what is the minimum distance from the embedded screw that I can drill a new hole?
Thanks all
Frank

 

[Steve Pierce]

Move it a drill a new hole. I have never had any success getting a broken #4 PK screw out of a spar cap.

 

[bob turner]

I agree - these things are hardened. Move the new hole several diameters laterally - do not try to drill close to the broken screw.

I found that new holes really need to be “threaded.” I used a longer #4 held in a small visegrip plier. I also found that my “tap” screw was only good for about ten holes before it, too, snapped. And finally, you need a $25 screwdriver - I got mine off the Snap On truck.

 

[Steve Pierce]

Steel screws from Dakota Cub. I do not use the stainless ones from Univair any longer.

 

[bob turner]

Agree - and "B" type, so they don't have sharp points.

 

[coxcub]

Thanks Steve and Bob - I'll leave it where it is and drill a new hole.
Frank

 

[Scott 2020]

Aircraft spruce have carbide drill bits in many small sizes.