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Thank you - all! 

[Mr Modifier]

I bought a Scaleauto 0.95mm replacement tip and made my own handle.  The 0.95 tip is actually tapered from 0.9 to 0.95 and will loosen and tighten M2 grub screws that my standard 0.9mm keys simply rotate inside.

[CMOTD]

That's more of the problem I'm getting too. UNDOING the blessed things!

Next question would be : What sizes do I need? Seems like there are three? but do I refer to the Mx size when buying, or the 0.9mm?

If you bought the car second hand then the previous owner over tightened them and you are stuck with the problem. If you bought the car new then the manufacturer is at fault and you are entitled to return it for replacement. If you over  tightened them yourself without a torque wrench then it is your fault and you are stuck with the problem.

No need to buy three different sizes, the decent makes all have removable/replaceable tips. Just buy one size with different spare tips and change as necessary. Mind you the tips are held in with a grub screw, what happens if you over tighten that and it gets stuck?

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All bar two of my cars are 'pre-raced' (although a third new one is on its way  ) so I have accumulated one or two 'problem cars', which is fine.

However, I have more cars in the stable to experiment with HAD I bought new - and the Collector in me is not worried about damaging them by 'fettling' or racing them either, which I would have done with new.

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Well I've gone with a Scaleauto Pro tool handle and three hex keys, the 0.9, 1.3 and 1.5, simply because I liked the idea of the taper on the Scaleauto 0.9.

Perhaps it'll work. 

[slotloco]

Torque wrenches are obviously the way to go, but is it really the case that, say, all m2 grub screw need to be tightened to the same torque whatever they are doing on the car, eg tightening an Ali wheel onto an axle or tightening a plastic one?

But in the absence of a torque wrench, in a way it might be preferable for the driver to fail first rather than ending up using the worlds strongest driver and rounding off all your grub screws.

I do strongly suggest you buy a torque wrench if you don't own one.

If tightening on wheels or spur gears - or certain pinions in the case of M2.5, the torque drivers work equally well for all.
There are no grub screws on plastic wheels ! (unless you have done a cunning thing an engineer in our club has created recently, but that is another story.)

I do strongly suggest you buy a torque wrench if you don't own one.

When removing, the driver doesn't work "in reverse" it acts like a fixed shaft hex driver. So if the grub screw has been mercilously over tightened, it is possible to have a failure.
- You may end up using a puller to remove a wheel from an axle in such cases, as drilling out "in situ" is difficult.
Fortunately, once you have drilled out a locked grub, you may be able to re-thread the wheel with the next size up - or in the case of some brand wheels like Slot.it - use the other thread on the other side of the wheel, as they give you two threaded holes.

I do strongly suggest you buy a torque wrench if you don't own one.

Unsure about your last sentence, but in the words of my mother, which shall never leave me - "Don't; just don't"
- I think Hollywood and the internet stole it from her.
If you don't use a torque wrench to tighten - only slightly tighten, really softly, and if a wheel falls off, tighten it slightly more the next time.

I do strongly suggest you buy a torque wrench if you don't own one.

I cannot remember the last time a member of our club lost an aluminium wheel, and they don't all own torque wrenches.

I do strongly suggest you buy a torque wrench if you don't own one.
 The removable tip ones are fine if you have the patience to change tips.

[BAracer]

Mr Loco

Understood, loud and clear. 

BAR

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Thanks to all for the advice.

The Pendle's 'Care Package' arrived this morning and the ScaleAuto 0.95 hex tip has done the job, loosening and (not over  ...) tightening the grub screws other tips wouldn't touch.  

I trust the other two sizes will also do the job. I bought one handle as it was the only way to get the 0.95 tip. However I have a set of collets and chucks that the tips will fit, so won't need another hex key to swap them over when required.

All's right with the World again. 

[Top Down]

Just a bit of feedback on the Slot.it hex keys. 

Been using them, or at least the 0.95 tip, quite a lot since 03/02/20 and it continues to undo grub screws others won't touch - and does them up finger tight without damage, or the wheels or gears letting go during running. 

So thanks to everyone for the advice.

I'm really happy with these but safe in the knowledge there is another option - ratchet keys - if I ever need to step it up a gear 

[Savage GT]

Sorry to jump in, but on a related note does anyone know what size the new slot it motor screws use ?
My NSR and Slot it Hex drivers don't work, and although I have a variety of both metric and imperial hex keys, nothing seem to fit properly.
The result being when I eventually get them undone I throw them away and fit a crosshead screw 
It would be handy to know what I need so I can get a specific tool for the job