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Use something like this. Gently does it.
http://www.screwfix.com/p/erbauer-drill-saw-set-3-pieces/89079?kpid=89079&gclid=Cj0KCQjwub7NBRDJARIsAP7wlT-RoPIzg67wPRD0mVTHgh2NlEncHGFwGw_yZAiSLqAaOmd3RWqrT-caAij7EALw_wcB&gclsrc=aw.ds&dclid=COb-nLXKkdYCFRCtUQodr-4PwQOr these or similar
https://www.amazon.co.uk/Tungsten-steel-Carbide-Dremel-Rotary/dp/B00CYA6I46 -
If you can locate one of these I can certainly vouch for its efficacy.
http://www.leevalley.com/en/wood/page.aspx?p=32279&cat=1,180,42240,53317
I think I might be able to get the Radials to fit if I can make the holes longer that attach to the brake bolt.
I have tried drilling but does seem to do anything with my drill bits!
Anyone know how I can make the holes longer to give the three more clearance?