Drill out a carbon steel screw :-o

[Dave did what]

Hi Firstly yes I am a DIY novice.
Trying to fit front roof bar on a 12 year old ford fiesta. Its a bit of a job.. have to excavate the holes and remove plastic plugs before you can bolt into them. But back bar all went fine.
Front plugs didn't want to come out and just bored out really soft plastic heads.
Soooooooo I screwed in some screws and then glued in said screws, to the plugs. One of them screwed out fine. With the other, the head sheered off.

Have tried to drill with my standard cobalt bits as have a bodyshop, no luck.
Also they tried to tap it through - again no movement.

IS it possible to drill through this screw? it turns out it is carbon steel I'm happy to invest in the specialist drillbits and cutting oil because the alternative is very invasive 3 figures job at the bodyshop involving a lot more collateral damage, welding, resealing etc.
Does anybody have any experience of drilling through a carbon steel screw like this?

BTW yes I know this is a ridiculous sequence of events I have overseen

Thanks

 

[JohnD]

if you can get some left-handed drills, the torque, heat and vibration will often wind a screw out. If it doesn't, it should eventually drill the head off.

I'm surprised your cobalt drills aren't working.

 

[lostinthelight]

Doesnt look enough solid meat in the centre to drill? if you kept heating a thin wall tube that just slid over the thread once the head is off and pushed it down in the plug it may bore in far enough to free it

 

[Dave did what]

if you can get some left-handed drills, the torque, heat and vibration will often wind a screw out. If it doesn't, it should eventually drill the head off.

I'm surprised your cobalt drills aren't working.

Not quite sure what you mean about drilling the heads off... There are indeed no heads left and that's my problem.
This plastic plug was stuck in before I glued in and then broke the head a carbon steel Screw. It's definitely not gonna wind itself out now.

Yeah apparently cobalt bits don't make much impact on carbon steel..

 

[Tigercubrider]

Could you dissolve the plastic? Or use an induction heater?

 

[Dave did what]

Doesnt look enough solid meat in the centre to drill? if you kept heating a thin wall tube that just slid over the thread once the head is off and pushed it down in the plug it may bore in far enough to free it

Yeah by drill it I basically meant obliterate it haha but anyway are your suggesting that a correctly sized/heated metal tube could slice through the surrounding plastic? That sounds appealing in theory.... Albeit well beyond my current capability.

 

[Dave did what]

Could you dissolve the plastic? Or use an induction heater?

Dissolving the plastic and or heating the screw to soften it are all sounding very interesting. What tool would you buy for that? Have you done this before?

 

[lostinthelight]

Dissolving the plastic and or heating the screw to soften it are all sounding very interesting. What tool would you buy for that? Have you done this before?

Like I said, you keep heating the tube till it melts its way down.

 

[Lower]

Find someone with a mig welder and get them to tack something onto the sheared screw.

 

[lostinthelight]

Find someone with a mig welder and get them to tack something onto the sheared screw.

If its surrounded in plastic theres no way to earth

 

[Dave did what]

Like I said, you keep heating the tube till it melts its way down.

Thanks ok what sort of tube would you buy for that and how would you heat it? I'm hearing induction mentioned... Is that something that can be used on this small scale?

 

[Lower]

If its surrounded in plastic theres no way to earth

Earth whatever you’re tacking the screw to and make sure they’re both in contact when you tack.

 

[Tigercubrider]

Acetone may dissolve the plastic.
A soldering iron might heat the screw but a mechanic's induction heater can heat bolts

 

[Dave did what]

Earth whatever you’re tacking the screw to and make sure they’re both in contact when you tack.

Yeah I think this is something a bit hard to grasp.. the screw in question is barely visible in the picture because it is lodged glued into the plastic plug which is in turn also stuck in its hole.

The screw you can see in the picture are there to illustrate what the pieces are, that are stuck.

That said, from the inside of the car, if you peel back the trim you can access the tip of the screw LOL

 

[conny]

Can you peel back the trim inside the car to a reasonable distance, or protect it from heat in some way?
From the outside play a fine, but fierce, blow torch flame on the remaining 'head' of the screw. This will put instant heat into the screw which should help to soften/melt the plastic plug. If you could have someone else inside the car with a suitable pin punch it may then be able to tap the screw out backwards while the plug is soft, or even destroyed.
The secret is to get the screw hot as quickly as possible before residual heat travels to surrounding metal areas.