You didn't mention which router you have. My Bosch (assembled in Mexico) 1617 has both quarter and half inch collets that are interchangable. Check on the web for a half inch collet for your brand of router. If you can't get a half inch for your router, I'd follow the advice of getting a router that has one. I agree that a quarter inch shank is probably too small for a large bit, and if your router is underpowered, you will have to make many light passes at very slow feed rate or risk. By getting a stronger new or used router with half inch collet you'll have a safer, more successful experience. By the way, welcome to the forum, many very nice and helpful people here with LOTS of experience.