How to undo a thread-locked connecting screw (barrel screw)?

[MickBee]

I need to undo the connecting screws which are holding door handles on. After I first fitted them (many years ago) I got tired of them continually coming loose, so I applied what was described as a removable thread-locking fluid; for some of them, this has turned out to be more permanent than I wanted.
I have tried applying heat (using a 50W soldering iron on one end and a 25W ditto on the other) but that hasn't worked.
All the usual suggestions for removing stubborn screws assume that the thread is firmly attached and rigid; in my situation, the screws will rotate together and I cannot apply enough torque (holding a slotted screwdriver into each end) to break the seal. I have removed one of the screws that will come apart - see photos - there is about 10mm of thread that needs to be undone. The bolts are 4mm diameter and 40 mm long, with domed heads and screwdriver slots 1mm wide and 7mm across. The material is not very strong - on some of them it has got a bit chewed up.

 

[just pumps]

No point in heating the long screw side as the heat will take an age to travel the length of the screw and I doubt it will ever get hot enough to soften the thread locker.

 

[MickBee]

I agree - my problem is that I can't tell which is the long screw side - both ends are similar.

 

[foxhole]

Stronger wrists or maybe impact driver on one side while holding the other as steady as possible .

 

[cdbe]

Someone with a good screwdriver on one side and you with an impact driver on the other. Only good thing is that you can easily buy replacements of those screws.

 

[JohnD]

you need an assistant working from the other side

and two screwdrivers that are unworn and exactly the correct size to fit the slot.

you can get screwdrivers with an octagonal shaft that a spanner will fit for extra grip.

If one of the heads gets damaged, you can drill the head off. Once you have made a pilot hole in the centre, you can either use a drill the diameter of the shaft, or a conical countersink. As soon as the head comes off you can push it through.

I used to have a jewellers blowtorch with a tiny tiny blue flame that would heat a screwhead.

Do you need to keep the old handle?

 

[MickBee]

Thanks for the helpful replies. To clarify some of the points raised:

• I do want to keep the 3 handles which each have a couple of stuck screws - the other 8 handles can be undone. (I want to undo all the handles to allow for repainting the doors - and to be able to in case a lock mechanism needs attention.)
• Two people:- yes but stronger wrists:- not at our ages, and getting outside help not so easy in these pandemic times. Screwdrivers with octagonal shafts could get round the torque issue though.
• Drilling one of the screw heads off - presumably starting with a 1mm bit to fit in the slot and then gradually increasing the size, while the screw on the other side is being held to stop it rotating? Any suggestions for types/makes of drill bit as I usually only drill into wood?
• Jeweller's blowtorch - worth a shot if the drilling doesn't work, but I'd have to get hold of one.

I'll update with progress (or lack thereof.)

 

[JohnD]

on ebay you can buy drills singly, or multiples in particular sizes, which is cheaper than buying a single or a set in a DIY shop. HSS twist drills are the usual thing, and I expect the metal used for those screws will not be anything special.

The reason for buying multiple drills is that in small sizes they are easily broken, especially using a hand drill on an uneven surface like a damaged screw head.

You can also get cobalt drills, which are used for hard steel, but I doubt you need them.