Posted 03 April 2017 - 12:18 PM
2 inch is only 50.8mm and is not accurate enough and you will be filing for ever if you bore them that size. They really are 52mm and always have been, long before metric nuts and bolts became standard in the UK.
Screwfix or B&Q will have a 52mm hole cutter. Don't bother with the multiple size sets made of spring steel. The thick ones with hardened teeth work well, and you can get a quick change arbor so you can change the cutter for other sizes.
Widely used by electricians and plumbers.
You can cut through the web of an RSJ with one so they will have no problem with typical dashboard materials.