How to remove a stripped dome-head screw?

[Ben Ritchie]

I need to remove a screw from a focuser assembly - problem being that it's a small dome-head screw (no way to get pliers around it) with a hexagonal allen-key centre that has been stripped by someone previously failing to remove it. Forget what size key it needs, but very small (2mm maybe).

Any suggestions about how to go about getting it out? Attached to a rather nice refractor, so anything involving force is a no-go and I need to get a replacement screw into the focuser thread so don't want to drill it.

Can grab pictures if they help explain the problem better

[Kai]

If its small then could you not use a blob of araldite / chemical metal and glue a nail too it. Use the nail as a lever to undo it.

Just a thought Ben

[GazOC]

Drill it out?

[keithatrochdale]

Can you get a Dremmel with a cutting disc on it and cut a slot for a flat screwdriver?

A picture or two might help us.

[skye at night]

Hello,

you can get those cutting driver bits that bite into the material as it turns and pullit out...

also.. 'old carpenters trick for painted over and stripped screws'

as usually it is 'stripped' in the 'loosen' direction..

try to actually tighten the screw...

You usually have better purchase and if it moves ANY.. it is very likely to then reverse easier.

works on wood... anyway.

If no purchase either way.. I would cut the slot as suggested above and make sure you replace with decent S/S hex nut...

Steve

[Ben Ritchie]

Ok, pictures

The problematic screw is the one on the bottom left, doesn't look too bad but seems fully stripped - the other picture shows the side profile of one I can remove. The allen key is 5/64ths

[skye at night]

I would suspect that at some time it has been turned with a 'too small' allen key (maybe imperial where it should have been metric or v/v)

Maybe try to fit in a slightly larger size ??

Worked with our dreadfully stripped car roof rail bolts...

Or big pair of grips...

Would hold off driling it out as a last resort personally,

Steve

[Ben Ritchie]

I would suspect that at some time it has been turned with a 'too small' allen key (maybe imperial where it should have been metric or v/v)

I think you're right - it will be imperial (it's a US-made focuser) and 5/64ths appears exact for the other screws. They're fairly gummed up though, so i'm not surprised an incorrect-size key would strip it.

[Leegsi]

I use TORX sockets to undo rounded off hex heads

[JohnC]

I had a simalar problem a while ago.

the bottom plate on mine was totally flat, so i took out the three screws that were ok and then gentley tapped the plate in a rotational way to release the stubborn screw. May be worth a try.

[MikeP]

Use a screw extractor - you can buy sets of them for peanuts. You just drill into the screw (if necessary) and then screw a screw extractor into the screw. It has a thread that "goes the opposite way" so as you tighten it into the screw, it starts to undo the screw.

(Too many screws in the above).

Mike

[Ben Ritchie]

Thanks all - lots of options there. Will have a go tomorrow and report back!

[MikeP]

Google strikes again. Screw or Bolt Extractor - How to Remove a Broken Screw

Mike

[brendant]

If the plate can rotate, remove the other three screws then try and rotate the plate in the a counter clockwise direction to loosen the screw, if you are lucky it will loosen and you may then be able to unscrew normally. If that fails try with a the Torx bit, it may go in with a few taps of a hammer if is close in size.

The other option is to use a dremmel to greate a slot in the head, or maybe a junior hacksaw.

I would only go down the thread extractor route if the others do not work as with small screws you are more likely to break the extractor and end up in an even bigger mess.

If all the above fail, remove the three other screws, file or grind the head off, this will allow you to get the plate off leaving a stump of bolt which you can then catch with a pliers or mole grip to unscrew fully.

Brendan

[Odd Dob]

Use a screw extractor - you can buy sets of them for peanuts. You just drill into the screw (if necessary) and then screw a screw extractor into the screw. It has a thread that "goes the opposite way" so as you tighten it into the screw, it starts to undo the screw.

(Too many screws in the above).

Mike

A-HA! I never knew of these things before. I might give this a go on these busted bolts I have on my motorbike which I've been puzzling over. You are my new hero.

[tinvek]

if your brave enough, try lightly tapping a torx bit into the end of the screw and then gently slacken the screw. if you pick a torx thats just a bit larger than the damaged allen key hole it should tap in pretty easily.

[Rogue Leader]

A-HA! I never knew of these things before. I might give this a go on these busted bolts I have on my motorbike which I've been puzzling over. You are my new hero.

A word of warning DO NOT be too ham fisted with these. If you snap them they are a bitch to get out as they are (should be) hardened, if the screw is going to come out it will. The extractors will take some turning but you cannot hang off them. Small screws like the OP problem are fine but bigger stuff especially if it is seized can be a problem if you are not used to them.

If your snapped bolts are proud get a stud extractor that grips around them if you have the space, if not or they are under flush get the stud as flat as you can, center pop and drill, then increase the drill size in small increments finally cleaning out with a tap of the correct size.

Sometimes a bit of localised heat can help, and sometimes you have just got to go for a full drill out with an oversize retap or a helicoil.

If they are snapped off in a plate that you can remove, center pop and drill from the rear, when the drill catches 9 times out of 10 it will unscrew the snapped portion from the plate for you, assuming they are not left hand thread.

Umm that probably went on longer than intended to be honest, you cant tell I`m a engineer that works on ancient large knackered machinery most of the time?, no oh good................... gets coat.

[barkis]

Remove the three good screws. Cut a slot into the bad one to take the blade of an ordinary screwdriver, then using the plate as a lever to pull the head of the damaged screw up at the same time as undoing it with the driver.

Ron.

[Merlin66]

I agree with Barkis.. cut a slot and use a flat blade screwdriver.

I experienced a similar problem when re-building the Lx200 mount.

The dec cover plate had a screw that wouldn't budge..

ended up putting a small weld tack on the head then used mole grips to get it to rotate...

[AndyKeogh]

In addition to all the above helpful suggestions You might like to apply some WD40 round the screw head to help ease its extraction

Andy

[TheThing]

or if you have no WD40, vinegar can often help release rusted in screws and nuts (my dad swore by vinegar when he was a submarine engineer).

[Milamber]

I am with Leegsi and Tinvek. Tap an oversized Torx bit into the hole - one that will *almost* fit in the current hole but not quite. That way it will cut it's own corners/ presses loose steel into the flats on the way in. Then it is a case of *lots* of pressure on as you slowly undo it.

Arthur

[Ben Ritchie]

All sorted, thanks guys - in the end cut a slot in the screw for a flat-head screwdriver, that didn't immediately work with modest effort with the screwdriver (as the screws were soft Aluminium (?) I was worried that i'd make things even worse if I applied too much force and the screwdriver slipped) but a bit of WD40, ten minutes to soak in, and out it came.

Very corroded at the base of the screw, which is why it was such a battle to remove.

Now have stainless replacements in place, along with the smooth (but very ugly!) TeleVue dual-speed...

[barkis]

Use a screw extractor - you can buy sets of them for peanuts. You just drill into the screw (if necessary) and then screw a screw extractor into the screw. It has a thread that "goes the opposite way" so as you tighten it into the screw, it starts to undo the screw.

(Too many screws in the above).

Mike

Not that many, only 8 including the one in brackets, but it took that many to explain the procedure.

[TheThing]

Argh! He counted! Hope it's clear round your way tonight barkis. You need to get out more!