[Cory]

Originally Posted by frcguy

I'm still learning a lot of this stuff, but I believe one of the reasons to have multiple collets is to be able to quickly switch in commonly used tools without having to undo the collet and change the tool. As far as where to find them besides eBay, you could check Craigslist, industrial auctions, or maybe ask local machine shops if they have any.

Edit: Also what Cory said.

You will have to unscrew the drawbar and remove the tool and collet for each (different size) tool you want to use. That won't change based on how many collets you have. You'd need something like an end mill holder or a collet chuck (which would use ER or some similar collapsible collet series) to be able to leave the tool in the holder. All standard collets for manual milling machines are going to be smooth bore that a tool will freely slide in and out of when not actively clamped by the machine.