Fitting parking sensors - what drill bit?

[wfdTamar]

I'm putting in parking sensors so need to drill 18mm holes in the plastic bumpers (Skoda Octavia). Just wondering what type of drill bit people have used. I think there are locations moulded in on the reverse side, so a small hole drilled through from the back then drill the main hole from the painted side. I'm thinking spade bit?

Irwin 4x Blue Groove Flat Bit 18mm | eBay

[Umai Naa!!]

I prefer spade bits, but have used holesaws and uni-bits in the past.

Spade bits usually do a pretty neat job, with minimal filing. Make sure you've got a needle file, or even a de-burring tool on hand to clean up the hole.

There are moulded lines and circles on the inside of the bumper, but from experience, they don't always line up with where the instructions say to put the holes. The Genuine instructions say dead centre of the badge emblem is your reference point, but this might be tricky with the Skoda.