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Broken metal screws in metal


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Hi working on a Mercedes 300 SL and I am quite a ways into the build actually at stage 74. All along when screwing screws into metal, I always dipped the screw in oil before tightening it. So far so good except today even after applying oil, a screw snapped with most of it still in the hole.  Any suggestions on how to remove the broken part from the hole? 

Gluing the part is not an option as it is a fairly heavy part that needs to be attached. Should I use a drill bit and try to remove it that way? 

Any suggestions would be appreciated.

Thanks

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Usually removing standard sized snapped screws is a difficult job, but in this instance since we're using seriously tiny screws it makes the job.... much, much harder to resolve.

Drilling out is difficult and could cause more problems. ie. damaging threads.

But since you oiled the screw prior to fit, removal should be slightly easier.

I propose to get a small hammer and a very small flat screwdriver with a hardened tip, or even better just a hardened pointed tool.  The object here is to try and etch in a deep mark (make an indent) in one side of the snapped screw head (near the edge). Once a mark is made in the screw head,  use the tool and the hammer to tap the damaged  screw in a counterclockwise direction.  Hopefully this will loosen the screw enough that it will just unwind and pop out with no damage to internal threads.  Hope that makes some sense.

If the indent you make is deep enough for the tool to bite and right on the edge of the damaged screw, you should be able to make some progress.  Mark the screw edge and the chassis with a permanent marker so you can see any small movement as you tap away.  🙂  Good luck.

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  • 4 months later...

Although presumably too late to help laverdj, as a tip for the future might it have been possible to remove the remaining screws, remove the part, then remove the broken screw with some pliers?

Certainly the use of oil when screwing into metal is a good idea.  However I go one further.  Without having the part to be attached in place, dip one of the type of screw to be used in oil, then screw it home [screw in for a turn, then out for half a turn.  In a turn, out a half.  Repeat this until the screw is home.] once the screw has hit the bottom of the hole, back it out all the way.  Repeat this for all the screw holes for the part in question.  Once complete, you can offer the part up and screw it in easily - once you start to get resistance, you know the part is tightly secured and stop turning the screw.

The other benefit will be that if a screw breaks, you should have more of the screw showing - or at least any slight damage you do removing it will be covered by the part you want to attach.

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Its been a while, and I did find a solution that worked. Since the screw was not in a visible part of the body, I decided to bite the bullit and  "drill" it out very carefully.

I managed not to damage anything and then used a slightly bigger screw than recommended and it did the trick

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8 hours ago, laverdj said:

Its been a while, and I did find a solution that worked. Since the screw was not in a visible part of the body, I decided to bite the bullit and  "drill" it out very carefully.

I managed not to damage anything and then used a slightly bigger screw than recommended and it did the trick

Good Job - Your now a specialist 😉

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  • 4 months later...
  • 10 months later...

The easiest way is to use a Dremel drill with a very fine metal drill.

Take your time, the hardest part is to keep the drill straight.. Once all the metal of the broken screw is out, you can now insert a new screw.

Should you F... it up, use a larger drill, no oil, drill it all out and refill the hole afterwards with "liquid metal". Let it harden out, and drill a new hole in the hardened filler for the new screw.

TIP: to avoid broken screws... screw it gently in... once you feel resistance, screw it a bit out, and screw it again and a bit further, then go back again etc till it's all in. You should never screw it all the way in in one time.  Forth and back with some oil is the safe way to go.

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  • 1 year later...

Very small metal screws can be a real pain in the rear when they sheer off ( usually flush with the surface being screwed into) so using pliers is impossible. Drilling out unfortunately is the only option. The brass screws used in the old Pocher classics had a habit of doing this. 

Oiling screws has already been suggested, but the only real way to prevent your screws from sticking in the part and shearing off is to find out your screw sizes and invest in some matching thread taps and a very small tee shaped tap wrench for them from a  model engineering supplier. Lubricate the tap with a drop of oil or rubbing across a wax candle. The holes in the model have been tapped during manufacture but invariably some residue often gets stuck in the holes and causes a problem. So running a matching sized tap through EVERY threaded hole before assembly is highly recommended to free up the threads on the holes beforehand.

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