Any ideas how to undo these screws?

I need to remove six off 4BA countersunk socket head fixings to dismantle a camera tripod (to cure a damping fluid leak).

I have good quality Allen keys but all six screws have resisted all the techniques that I know of or have used successfully previously. The problem in this case is the limited height above the screw head.

There is about 65mm between the two inside faces both of which have three fixings that hold the stub spindles. With extended drill bits the three fixings on one side could be drilled out but the drill would be about 20 degrees off axis so I'm not likely to have much success.

On fixings with clear access I have drilled out seized screws down to 8BA without sacrificing the tapped hole so 4BA are not normally a problem.

I do not have any welding equipment but I'm not sure how much damage might be done to the paintwork etc if a stud was attached to the screw head.

The six in this unit are standard steel Allen screws, ringed in red in the pictures. (Caliper is just for scale)

What I think I need is a miniature right angle dremel type tool to grind off the heads but I have not seen any tool small enough to fit in the gap.

Ian P

I'd try a nice sharp centre punch on the heads first turning them anticlockwise

Edited By Ian Parkin on 12/11/2016 17:46:59

Have you considered the possibility of the threads being left handed ?

Hi Ian

Interesting problem any chance the screws are Loctited? a trick I have herd of but not tried is to apply a red hot poker to the screw head and hope the heat breaks the joint. Dremel do make a right angle drive that screws on to the front of there machine or better Proxxen make a right angle mini drill but make sure you are sitting down when you ask the price! If you dare I some times fine a sharp tap with a centre punch at an angle beside the socket works.

Good luck Paul

Hi Ian

I think I'm with Paul on this a little heat perhaps from a soldering iron not a blow lamp though

Try holding the hot tip of an electrical soldering iron on the head for a couple of mins then a sharp tap with a centre punch.

Perhaps they are 'loctated' in place. They would need heat to break the bond, but how? I can't see a reason why they would be L.H. screws.

I am guessing that if you are using metric allen keys, then perhaps they are imperial size heads (or vice versa?). If the hex sockets are badly 'mashed' , I would carefully grind down the next size up hex key (imperial ??) and cut it off short, then wedge it into the hex socket, between the end of the hex wrench and the opposite face. Now, grip the hex key with mole grips and see if you can loosen them.
Another idea (not pretty), sacrifice the round plate by cutting slots into the ends of the hex heads by using a Dremel and thin cutting disc, then use the same idea as above. Again, try to get a bit of heat onto the screws - 75watt soldering iron with a good blob of solder on the end of it may be enough.
BobH

The 'blue' antivibration threadlockers will often relese just with a soldering iron on the head but the red stuff often takes more heat (for me).. one of those cheapo jet flame ciggie lighters can apply finely focussed heat: **LINK**

If the problem is getting enough pressure on the allen wrench while twisting it then I wonder if it'd be possible to knock up a simple slotted disc that the allen key long arm could sit in up against a thrust bearing round the short arm and clamp across the whole fixing? Extended leavage isn't going to be a problem but well worth trying a clockwise turn before anticlock just in case it is left handed.

Steel into alloy! Best try heating them with a large soldering iron.

My motorcycle rear disk's six bolts proved impossible to remove, in the end a local company bored them out and put inserts in, Loctite, salt, alloy and steel all got together to make sure the bolts were really tight

If heat fails, try a freezer spray.

Neil

The screws are not LH threads and not loctited but the tripod does get used in underwater filming so corrosion is likely. The tripod head is not designed for underwater use but they do survive amazingly well despite being mostly aluminium and (plated) steel construction.

I have an assortment of techniques and tools to remove seized screws and screws with chewed slots etc. Chisels and punches are not to relevant in this case because of limited access. Limited headroom rules out drilling too.

Small BA sizes of countersink screws have even smaller hex sizes, I regularly drive in a hardened Torx bit into a hex recess (sometimes even before I try the correct size Allen key), the impact from forming the Torx recess often loosens the fixing but the amount of torque that can be applied with the six lobes is far greater than that through a standard hexagon recess.

Heat is probably the best approach but a small screw in an aluminium casting is not going to get very hot with a soldering iron touching the screw head. I'm thinking that a copper slug (with pip to centralise), heated on the gas hob to near red, might transfer enough heat especially if I can make a fixture to apply axial pressure on the screw face.

Ian P

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Ian,

A slight variation on the theme ... Use a Weller [or similar] transformer-type Soldering Gun, and put a little snippet of Solder in the hex-socket ... You will get much more heat into the screw.

MichaelG.

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http://cpc.farnell.com/weller/8100ud/expert-soldering-gun-qa/dp/WL8100UD

Edited By Michael Gilligan on 12/11/2016 19:47:23

The 6 mm hex drive bits are often a better starting point than an conventional L shape key. I have a couple of the inexpensive ratchet type levers which I find can be much eaiser to keep straight in a small hex socket. Especially so in restricted spaces like that where a fingers and thumb pinch grip between the knob on top of the tool and the main body can be used to keep the key properly seated. I've even resorted to crushable spacers or screw things to keep the keyin place during the first final half turn. Helps that small screws are fine threads so there isn't much jacking effort as things start to move.

6 mm hex drive bits are cheap and commonplace these days so wrecking one or two to rescue an expensive piece of kit is no big deal. Just ended up with more "muticates" after buying one of Mr Lidls sets to get some security type bits I don't already have.

Clive

I think Clive is on the tight track here 6mm drive bit with some sort of screwjack (can be just a nut and bolt) to force the key into the screw with some considerable force. Allen keys are great at climbing out of the screw head because no axial force can be applied. use a spanner on the bit . Once the screw has undone 1/8 turn you are on the home straight.

steel + aluminium + salt water = battery

I suspect those threads have corroded up badly

Would have thought you need to heat up the alloy as it will expand more than the steel.

There's always a hot air gun, the Titan one from screwfix is cheap and quite good just remove any plastic

I have both 1/4" and 4mm AF bits and do have a means of applying pressure but hex and Torx drive systems do not generate any 'cam-out' force as they are parallel sided.

In this case the drive torque is limited by the small size of the recess, The six torque transmitting contact areas of the key in the recess are dwarfed by the conical contact area of the head on its own before even taking threaded contact into account.

An eighth of a turn, I'd be quite happy with a twentieth!

Ian P

If I can get the screws out I will be able to remove the plastic (and the damping fluid)

Ian P

Cut deep slots in the heads with a dremel. Will damage the surrounding part but that can be filled with liquid metal later

Use a right angled screwdriver to turn the screws. Pack a piece of timber between the opposite side & the return angle of the screwdriver to help apply pressure to keep the blade in the screw such that by pulling the arm outwards as you turn it pushes the blade inwards onto the screw

Edited By Sam Longley 1 on 12/11/2016 21:15:32

I would like to cut slots without damaging the flange by using a small diameter (maybe 8mm) cutting disk in the Dremel but its difficult to get the disk at right angles to the screw axis unless the disk has a very long mandrel.

Ideally I would use a 1mm or so diameter diamond coated or carbide burr to create the slot but that would need a very short or a right angle Dremel tool.

I've just had a thought... what I need is an angled dental handpiece, I'm sure they exist, so now to find one.

Ian P

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Given that they are countersunk screws, it's more likely that the troublesome corrosion is in the countersink.

This has two significant effects:

1. There is a large area of adhesion
2. The thickness of the corrosion layer tensions the thread

Heat to the head of the screw, immediately followed by application of some penetrating fluid [PlusGas formula A] to the warm joint-line would be my best bet.

MichaelG.