Depressed center wheels may also be referred to as raised hub wheels or by their shape designation Type 27, 28 or 29, with Type 27 being the most popular. The depressed center design allows the flange/lock nut to recess within the wheel so that it can be used for various grinding and cutting applications. Depressed center wheels are designed to handle the most severe right angle grinding applications from heavy stock removal to rough blending. More recently, depressed center wheels have been designed for cut-off applications when the tool is proper designed with flanges and guards. While large right angle grinders (7 in & 9 in) have been around for many years, small or mini grinders that handle 4 in, 4-1/2 in and 5 in wheels have made this machine, and wheel category, the most popular in power tools.

Norton® Gemini® Depressed Center Wheel, 4-1/2 in Wheel Diameter, 1/8 in Wheel Thickness, 7/8 in Center Hole, Arbor Connector, 24 Grit, Very Coarse Grade, Silicon Carbide Abrasive, Wheel Type Number: Type 27, 13580 rpm Maximum, Resin Bond, Applicable Materials: Concrete, Masonry, Asphalt and Non-Ferrous Metals, Specifications Met: ANSI Specified

• Sharp silicon carbide grain for penetration of very hard non-metallic materials
• 1/8 in are designed to be used at a 90 deg angle for offhand cut-off, notching or cleaning pipes and weld beads
• Blend of hardness and bond to provide the best mix of cut rate and life
• Good choice when low initial price is needed for small jobs or inexperienced operators