Roll bars part 2

After the 2 front hole had been drilled it was time to open them out to accept the roll hoops
The hoops are 51 mm Diameter and reading blogs the ideal bottom hole to allow for movement is 55mm

Started by drilling with a hole saw to 50 mm, however I didn't want to drill with a standard hole saw for 2 reasons first is its a 6mm drill going in a 10mm hole so ahs the potential to go out of line and second didn't want the drill to take any of the powder coating off the chassis as its was going though .
Hit on the idea of putting some 6mm stud bar instead of the drill and wrapping it with adhesive tape to make it appear 10mm.
Worked like a treat .

hole saw with the modified centre ( after drilling 4 holes )

 Happily drilled the 4 holes to 50 mm which gave me the opportunity to dremmel the holes out to 55 mm and correct any errors .

first hole done

looking down the hole I could see that I was a little bit off centre but can be corrected

second hole note slightly out

Then came the fun bit how to dremel them out to 55mm and make the hole central, hard enough but even worse when there is no room , getting in the boot was fun but getting out another matter entirely .
again came up with an idea got a 12mm bolt and wedged it in some adhesive which had a diameter of 55mm ( eventually ) .

home made tool (note the back hole is smaller 44mm)

this seemed to work and filed the holes until the tool dropped in the hole result .

tool in action  

all four holes now 55mm . time for a glass or three