Hey guys the title sounds a bit fucked--I have helmet locks on my crash bars that I want to remove. They have those half head screws you can do up but cant undo--is there a tool that will undo them or do I grind them to a slot then replace the bolts when refitting?---cheers Grim

I dont know the bolts you're talking about, but i have battled a few anti-theft screws on cars.

You can often undo them by tapping them around with a hammer and centre punch. Once you get a divot in them you can get a bit of force onto them.
Failing that you can cut a slot as you suggested, or even spot weld on a nut if its not goint to cause any other damage.

cheers SAm----grim

Grim they are made that way so they are hard to remove and there is no tool..As Sam says they are the same as on the ignition lock housing on a car,you have to slot them or carefully grind the head of.If you are lucky you may be able to drill into the centre and use an EZYOUT or again weld a small bolt to the top

Hmmmm lots of guys with lotsa knowledge about anti theft screws!!! Hahahaha.  What a pain in the arse way to fit something to a bike, especially for a helmet lock. The lock is probably worth more than the helmet of favour on this site. Let us know how you deal with it Grim. Just out of interest.... u know.

 angle grinder