How do I remove rounded allen bolts?!

I'm removing an engine of which the drive shaft allen bolts are rounding off… i have the right size allen key but they are all knackered… is there a quick and easy way of removing them??

are you sure you have the right tool? all mine have been triple square drive not hex head.

 easiest way would be leave them on till the engine is out so remove hubs with engine, then cut heads off bolts with an angle grinder then when cv is off use grips to undo, shouldn't be that tight when cv is removed

Yea they are all hex head, i guess that is probably the quickest way… I'm guessing you'd have to lift the car off the engine to achieve it though?

in the past I have used a bit of heat and tapped a socket over them to get them off cant remember size of socket though maybe a 13mm or 14mm need to be a tight fit knock on with a big hammer
works a teat but use a old socket and not the hex kind

The drive shaft bots are 12 pointed star drive, someone may of used the wrong tool to remove them.
You can get new bolts.
To remove you can try and hammer in a slightly bigger spline tool and hope it grips to undo the bolt or a big pair of mole grips and grab the bolt to undo.

Right tool looks like this.
http://www.ebay.co.uk/itm/SPLINE-BIT-SOCKET-SET-by-BERGEN-TOOLS-Triple-Square-12-Point-M5-M6-M8-M10-M12-/251980872965?epid=2043371760&hash=item3aab3afd05:g:4TYAAOSwWJhZX7SM

Vice-Grip pliers, clamp them on the head and smack with a hammer they will break torque  then use a TORXs hand they usually come out easily.

They are not allens they are 8mm Triple Square, and the bit is like 10 bucks over here, you have to be sure that you Tap it fully in to seat it before you apply torque to tighten or remove.

33ft/lbs is all you torque them to.

He may well have hex head. 

My new bolts that came with my shafts are hex headed. I was expecting 12 spline too. 

I'd smack a socket over them. 

New bolts if needed?
Some CV kits come with new bolts in the box.

http://www.ebay.co.uk/itm/VW-GOLF-MK1-1-6-1-8-GTI-MK2-1-3-1-8-GTI-INNER-CV-BOLTS-SET-C181-/200806579563?hash=item2ec1013d6b:m:m1A3IxPMjugehjDRLWiG_VQ

They were hex head… managed to hammer a 12mm socket over them and got them out. Just took a lot longer than originally planed… still only 3 engine mounts and it'll be out hopefully Monday lunch time it will be in the workshop ready to be stripped down. Thanks for all the tips and help guys!!!

Haha I literally just did this myself. 

Luckily for me, it was only 1. Again 12mm socket hammered over it done the trick. 

On my BMW 2002 I also stripped a few of the allen bolts.
I decided to just ground the head of them off and I was able to turn them loose by hand probably since the tension was removed from the whole bolt and the threads.

As long as it's not rust welded you should be fine.
Although I would suggest using a vice grip or a hammer and chisel to try and spin it loose first.