since you're drilling though a set of pinch welds I recommend getting a set of drill bits. Don't care which.
Or maybe consider re-sharpening with a bench grinder if you want to work that effort. not sure it's worth your time.
reasoning - body of modern car is often a high boron content - high tensile strength steel - if steel body. Those pinch welds are often multiple layers at a point - pinched together and then melted and hardened. Thus one of the hardest points in the car body.
Even a extra hard M42 or other machinist level drill bit won't like that job for long. How many holes do you have to drill? say it's 10, I'd plan on getting 3 bits and hoping I can cleanily make 3 holes per bit and I would put oil on them
Of brands Irwin hanson is pretty good quality, as is Norseman which is what I'd look for. but I'd give equal look at just getting some common HSS bits in the size I needed and considering them throw aways. Might be cheaper and easier in the long run.
DO you have to drill the 1/4 inch hole and then open it up - or just that size hole? How many?