The workhorse of the flex-shaft mandrels, and the most versatile, is the screw mandrel. A tiny screw is threaded through a hole in the center of a disk, wheel, buff, etc. and then into the end of the mandrel shank to hold everything together. The screws can be long or short to accommodate the width of the accessory.
There are different styles of screw mandrels: slim, heavy shouldered, etc. I like a plain mandrel with a 3⁄32-in. (2.4 mm)shank and a 1⁄16-in. (1.5 mm) screw. Screw mandrels have standard, right-hand threads and are used in the forward mode; however, left-hand threaded mandrels, which won’t unscrew when you’re using a wheel in reverse, are also available. (Un-like a drill, abrasive particles cut in any direction.) Oh, and the little washer under the screw? It’s there to grip thinner disks. Whether it’s above or below the disk makes no difference. Screw mandrels are usually sold in packages of six or ten.
There are also other mandrels, each designed to hold a specific accessory. Animal, vegetable, or mineral, if I can hold it on a mandrel, I’ll put it in my flex shaft. Which brings me to: