Is anything made that allows you to change a router with a quarter-inch collet into one with a half inch?
Carol Reed: Yes, your wallet. If your router is a fixed quarter-inch collet router, you are happily in the market for a new tool.
John Swanson: Most quarter-inch capacity routers do not have the horsepower needed to handle the larger diameter bits. Such routers are lightweight and are harder to control.
John Brock: If your router is big enough to handle a half-inch shank, then it probably came with a both half- and quarter-inch collets. I would check with the router manufacturer or distributor for replacement collets.