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...if using a correctly fitting driver?
Another tread talked about a rounded off allen bolt but in my experience I've only ever either snapped the bolt off or bent/snapped my allen keys.
Depends on size in my experience, I rounded two of my Allen keys the other day trying to undo a shimano pedal and the bolt was still fine. Whereas I have rounded a few <3mm bolts over the years ( admittedly not usually bike stuff)
Really? Of course it is. Poorly made heads, cheap/worn tools. Shallow heads. Alu bolts.
Can be avoided, but it certainly can happen.
Wot njee says. Work in a bike shop for a while and marvel at some folks (lack of) ability
imagine the tool that forms the female allen key socket being used reapedly for many hours, its going to become worn as are the holders that hold the bolt, so the female is going to become a sloopy fit.
Cheap tools very capable of rounding out. There is a reason some tools are cheap!!
Also dirt in the Hex head can cause it. Hex key then doesn't fully engage.
As above, if there is stuff in the recess and the Allen key isn't fully inserted, you can muller the head of a bolt even with the highest quality Allen keys.
Ball end ones seem to cause problems on smaller sized bolts
TIP , grind of the ends of a allen key if used quite a lot .
I've rounded out everything up to and including 8mm (not managed a 10mm.....yet).And up to Torx T35 (though they tend to snap before the head goes).
Yes !
Bell ends all ways cause problems.
I've rounded the bolt on one of my PDM540 pedals. You can buy it if you like, comes with a free Spesh Roubaix still attached. See my posting history or email in profile. 😉
I do it all the time :o(. I've two sets of handlebars with grips on that I can not get off due to rounded allen bolts. Hack saw will sort them out though :o)
yes
Yep, regularly when I worked in the print trade.
Litho machines are held together with cap screws, some of which need adjusting fairly regularly, and some of which you can only access with a ball-ended key... you can probably guess the rest...
The Mole Grips got used almost as much as the hex-keys...
Is it possible to round off an allen bolt
You work in an office don't you.
of course
[s]work[/s] take stuff into a bike shop and marvel at some [s]folks[/s] staffs (lack of) ability
I'm seeing lots of, yes using ball end, and when there's crud in the bolt etc.
I probably wasn't clear but by correctly fitting driver I mean none of the above.
I was talking about a perfect fitting driver in a clean and undamaged bolt.
I'm sure it's easy on a < 3mm bolt but 4mm upwards?
and yes singlespeedstu I do work in an office.
Yes. Too much torque. Soft or shallow heads etc etc. what a daft question. 😕
I"ve rarely come across an allen bolt that doesn't round off eventually. Cleat and stem bolts are the favourite. And yes I am very careful and try to use decent tools and not over-tighten them, but they always go. However I recently learned a great trick to undo them by hammering in a torx wrench head (from a socket set) the next size up. Done it three times now and it's always worked.
Those really low head height Hope m4 rotor bolts.
[url= http://en.wikipedia.org/wiki/No_such_thing_as_a_stupid_question ]I bow to your superior knowledge, njee20[/url]
I'm sure it's easy on a < 3mm bolt but 4mm upwards?
Yup. Just turn it the wrong way and something will give eventually.
Yes I have seen the aftermath.
I've seen the aftermath of someone threading pedals into the wrong side. Not just one, mind, both of them. **** knows how you do that, but if that's possible then rounding an Allen bolt is easy peasy.
I bow to your superior knowledge, njee20
I said daft, rather than stupid, more light hearted. I just don't see why you're actually asking, how can you even consider that it's an impossibility? Although then saying 'ill fitting tools notwithstanding' makes it a bit odd. Bit like saying 'can you actually get a puncture?' Then adding 'I mean without actually running over anything sharp'.
njee20, I admit I was being a bit vague, of course I don't think it impossible.
When I asked the 'daft' 😀 question I had in mind an M6 bolt similar to this
[img] 
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as this was the kind of bolt mentioned in another thread which was seized and apparently rounded off by a professional mechanic.
project - Memberso the female is going to become a sloppy fit...
Nowt worse than this... 😀
Are these damaged tools/heads the result of a lack of grease/copper-slip?
I currently have a steel On One frame which has a BB that is seized solid. 😈 It appears to have been put in dry? and I'm working through a few different scenarios on getting it out.
It's a UN26 so the plastic NDS cup can be chipped away at once the DS is removed. It is rusted firmly in place and I'm going to keep coming back to it over the winter. Extra leverage isn't really helping and my splined bb tool is crying out for mercy...
The Octalink cranks had really bad foot rub so I wanted to replace them with a spare set. They were functional though and I would have left them alone if I'd known how much of a ball-ache it was going to be...
Chest_rockwell if you haven't already tried give these a go
[img] 
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As above for the stuck BB, Plus Gas or other penetrating oil, either with a small applicator tube through the BB drain hole if it has one (Probably not), or pour it down the seat tube, and leave to stand for a while.
As to the OP, with a new clean screw of decent quality being fitted using a new decent quality tool in an easy access situation by a decent quality operator who is not tired, in a rush or needs a piss, then it is very hard to round off the head of an allen fixing. In any other situation all possible variables could affect the outcome.
No BB hole and I'm not in a hurry so I'm going to pour copious amounts of penetrating oil down the seat tube and forget about it for a while.
The BB shell thread is probably going to need chasing out if and when it comes out though...
Forget plus gas- Wurth rustoff is brilliant stuff.
(land rover tinkerer)
http://www.wurth.co.uk/technical-chemicals/lubricants-and-rust-removers/rust-removers/rost-off-ice-400ml
I always grind the hex key flat, even in a new set.
I had some old imperial keys that I ground down for removing rounded metric socket heads. A couple of taps into the slot & it generally got enough purchase to get it out.
For that bottom bracket, if it's plastic just cut it out.
Assuming your turning it the right way of course... 😉
Apologies for the hijack, Lakes Puma, but I was looking at DIY penetrating oil solutions and read this...
As I have a plastic NDS cup, the oil + acetone mix will probably eat through that before it has a chance to do it's thing on the other side but the results from the tests are interesting. The 'scientific rusting' is probably a hard thing to quantify and keep uniform of course.
[b]Recently “Machinist Workshop Magazine” did a test on penetrating oils. Using nuts and
bolts that they ‘scientifically rusted’ to a uniform degree by soaking in salt water, they then
tested the break-out torque required to loosen the nuts. They treated the nuts with a variety
of penetrants and measured the torque required to loosen them.
This is what they came up with:
Nothing: 516 lbs
WD-40: 238 lbs;
PB Blaster: 214 lbs;
Liquid Wrench: 127 lbs,
Kano Kroil: 106 lbs
(ATF)/Acetone mix (50/50): 50 lbs.
This last “shop brew” of 50% automatic transmission fluid and 50% acetone appears to beat
out the commercially prepared products costing far more.[/b]
Manage it all the time...
As I have a plastic NDS cup, the oil + acetone mix will probably eat through that before it has a chance to do it's thing on the other side but the results from the tests are interesting.
I very much doubt acetone will eat through plastic BB cup material, anyway, lay the frame with the drive side down, as that will get a better distribution of whatever you choose into the threads.
Obviously if you are doing this kind of job regularly then making your own brew is cost effective. If you do have acetone then you can substitute used fork oil for the ATF.
If the bolt has been fitted as new in a factory there is a fair chance they used an air driven tool, even if set to the correct torque they can still be super tight. I was taught many moons ago when checking the tightnees of any nut or bolt,to slacken it off,then tighten it. saved me many times.