Allen head bolt won't budge

[Peter Drew]

There must be some obscure law that dictates that there must be a minimum of 100 miles between engineers and amateur astronomers that need mechanical help. 

[Zakalwe]

I agree with Nigel - a left-hand threaded screw extractor may be your safest bet .... like these:

http://www.screwfix.com/p/screw-extractor-5-piece-set/18643

Hateful, hateful things. On small screws the torque required almost always causes them to snap and then you are left with something that only spark erosion will shift.

If you insist on using a screw extractor, then something like these are much better:

https://www.google.co.uk/shopping/product/4311940248256589621?q=screw+extractor+set+sealey&client=firefox-a&hs=Kdd&rls=org.mozilla:en-GB:official&bav=on.2,or.r_cp.r_qf.&bvm=bv.52288139,d.d2k,pv.xjs.s.en_US.xLLRitWY30w.O&biw=1680&bih=924&dpr=1&tch=1&ech=1ψ=Ets6UuDSLeOp0QX54oG4DA.1379588884095.3&sa=X&ei=F9s6UsLRAsiw0wXIrYGQBg&ved=0CHQQ8wIwBw

The absolute best screw extractors that I've ever used are these from Snap-on

http://buy1.snapon.com/catalog/item.asp?P65=&tool=all&item_ID=635454&group_ID=675455&store=&dir=catalog

I think that Sykes-Pickavant used to make them too.

If they won't shift it, then it ain't coming out.

[rob0971]

You could try the end of a larger screw extractor without drilling in the hex recess. The larger extractor is less likely to snap off. I have done this a few times in my time as an engineer.

[IanL]

Forget cutting a slot and using a screwdriver. I can never fathom why people suggest this. It never works on a stuck bolt.

As I said above, this has worked for me twice now on this type of bolt, on exactly the same OTA of the same vintage from the same manufacturer.  Since it did work, twice, that is why I suggested it.  I'm not an engineer, but it seems to me that if something has worked twice on a given piece of kit, there is a reasonable chance that it would work a third time.

[Zakalwe]

As I said above, this has worked for me twice now on this type of bolt, on exactly the same OTA of the same vintage from the same manufacturer.  Since it did work, twice, that is why I suggested it.  I'm not an engineer, but it seems to me that if something has worked twice on a given piece of kit, there is a reasonable chance that it would work a third time.

Fair enough...that makes sense, especially if you have had 1st hand experience

I've seen it recommended loads of times in cases where nuts have been rounded off, as a general way of removing seized bolts. If the nut is tight enough to round it off, then no screwdriver in the world will shift it.

I've learned, through bitter experience, that a lot of the causes of rounded bolts/screws is caused by using the wrong tools in the first place. Rubbish Allen keys, using cross-head screwdrivers on Fearson headed screws, incorrect spanner sizes and so on.

[Astrobits]

Fair enough...that makes sense, especially if you have had 1st hand experience

I've seen it recommended loads of times in cases where nuts have been rounded off, as a general way of removing seized bolts. If the nut is tight enough to round it off, then no screwdriver in the world will shift it.

I've learned, through bitter experience, that a lot of the causes of rounded bolts/screws is caused by using the wrong tools in the first place. Rubbish Allen keys, using cross-head screwdrivers on Fearson headed screws, incorrect spanner sizes and so on.

Too true. There is no substitute to using the correct sized quality tool. Cheap tools usually give problems not far down the line.

Nigel

[jetstream]

Might not have Kano Kroil on the Isle of Man, is it also known as penetrating oil? That could be found in a good DIY, hardware or car spares shop.

Kano Kroil http://www.kanolabs.com/ is available in UK and may be commonly used by some there.It is a penetrating oil-solvent based,and works better than anything else I(& others) have ever tried.It is an unusual product,very thin,a "dry" liquid that will creep into very small spaces-not much is needed.Personally,I would try a small amount of NON CORROSIVE penetrating oil,let it sit,then try to get it out with a set of VISE GRIPS or equivalent-what type of screw head is it?You know button head,regular allen key,etc.If no go then releasing tension by the means others have suggested is next.Using the Dremel works great,but can be challenging.Screw extractors work(I have a set) but I find them difficult on small bolts/screws.The main thing is have a plan.If plan "A" doesn't work,take a break,then try plan "B"-if anger starts setting in STOP.Take a break.An extra set of hands is a huge asset.

If steel is threaded into aluminum it can actually corrosion weld itself together,making removal extremely difficult.When I thread steel into aluminum I coat the threads with anti-corrosive-always.

[Zakalwe]

If steel is threaded into aluminum it can actually corrosion weld itself together,making removal extremely difficult.When I thread steel into aluminum I coat the threads with anti-corrosive-always.

Thats a really good point. Steel corrodes into "pits", whereas ally corrodes outwards as "fur". Steel and ally together tend to cause some galvanic corrosion when damp and lock together. A wee dab of anti-seize paste helps loads.

http://www.corrosionist.com/galvanic_corrosion_chart.htm

[Deano1]

Someone else might be able to say if it's a good idea or not, but a bit of heat might help out, wave a heat gun over the bolt head a bit. Usually works for me but on different applications, not sure if it's appropriate to heat up this particular part.

Interesting to hear all the tricks though, I have to say a good socket type allen key has helped me out a lot on engine stuff in the past.

Deano

[Mark Henthorne]

Success!!!

Well, I bit the bullet with a junior hacksaw, and with a great deal of care started to cut a slot. Once well on the way, I progressed to the full size hacksaw, again ever so carefully, in order to widen the half finished slot to the driver bit width, and then continue until I was happy it was deep enough to get a good purchase. With one of the flat blades (with proper machined concave surfaces so the blade does not jump out of the slot) inserted into the electric screwdriver, I slowly applied power, and yippee, it gave way! I honestly didn't expect it to.

For the record, I wouldn't be at all surprised if the heat generated by the cutting was a large help, as was suggested by one of you in relation to the idea of using a soldering iron to repeatedly heat and cool the Allen bolt.

Anyway, radius bracket now fitted, along with Losmandy plate. Thanks to everyone for some great ideas.

Mark

[JayStar]

+1 for cutting into the screw head - happened to me today on a new delivery of a CPC 925. One of the phillips head screws for holding the dovetail plate shredded completely when trying to remove it.  Cut it with a Dremel  - small circular saw attachment... straight headed screwdriver then released the screw. 5 minute job and easy.

[davefrance]

How about trying a screw extractor? Never tried them so cannot say if they would be suitable in this case. Just Google and you get all the necessary info.

Nigel

Socket head screws are heat treated so are much harder to drill than normal mild steel fasteners. You could try grinding two flats on the side of the head then use a large adjustable spanner to give you extra force. As stated by others above, soak first in a penetrating oil and leave to soak in overnight.