Foredom Screw Type Mandrel, 3/16" dia. Head/Shoulder x 1/16" dia Arbor Screw, 3/32 inch Shank, Style A-M1. For mounting wheels stones felt bobs small buffs and other unmounted accessories with 1/16" arbor holes. 1-3/4" overall length. 40000 RPM Max Speed. Screw type mandrels come with different shank sizes and arbor hole dimensions. When making your selection be sure the screw capacity of the mandrel matches the arbor hole of your accessory. Also check to see that the diameter of the mandrel's shank fits your handpiece collet (or chuck). The right fit will help to insure safety and keep your accessory running true. Maximum and recommended speeds depend on the type and size of accessory as well as the mandrel in use. The ratings we publish for our mandrels are based on a 1" overhang with an accessory that weighs under 1 gram and is smaller than 1/2" in diameter. As a general rule smaller accessories and mandrels can be used at higher speeds than larger accessories and mandrels. It is a good idea to follow the recommendations that come with both the accessory and the mandrel you are using.