Section R. 325.52502 - DefinitionsRule 2.
(1) "Abrasive cutting-off wheels" means organic-bonded wheels, the thickness of which is not more than one forty-eighth of their diameter for those up to, and including, 20 inches in diameter, and not more than one-sixtieth of their diameter for those larger than 20 inches in diameter, used for operations such as cutting, cutting off, grooving, slotting, coping, and jointing. The wheels may be any of the following: (a) "Solid" consisting of organic-bonded abrasive material throughout.(b) "Steel centered" consisting of a steel disc with a rim of organic-bonded material molded around the periphery.(c) "Inserted tooth" consisting of a steel disc with organic-bonded abrasive teeth or inserts mechanically secured around the periphery.(2) "Belts" means all power-driven, flexible, coated bands used for grinding, polishing, or buffing purposes.(3) "Branch pipe" means the part of an exhaust system piping that is connected directly to the hood or enclosure.(4) "Cradle" means a movable fixture, upon which the part to be ground or polished is placed.(5) "Disc wheels" means all power-driven rotatable discs faced with abrasive materials, artificial or natural, and used for grinding or polishing on the side of the assembled disc.(6) "Entry loss" means the loss in static pressure caused by air flowing into a duct or hood. It is generally expressed in inches of water gauge.(7) "Exhaust system" means a system consisting of branch pipes connected to hoods or enclosures, 1 or more header pipes, an exhaust fan, means for separating solid contaminants from the air flowing in the system, and a discharge stack to outside.(8) "Grinding wheels" means all power-driven rotatable grinding or abrasive wheels, except disc wheels as defined in this standard, consisting of abrasive particles held together by artificial or natural bonds and used for peripheral grinding.(9) "Header pipe (main pipe)" means a pipe into which 1 or more branch pipes enter and which connects such branch pipes to the remainder of the exhaust system.(10) "Hoods and enclosures" means the partial or complete enclosure around the wheel or disc through which air enters an exhaust system during operation.(11) "Horizontal double-spindle disc grinder" means a grinding machine carrying 2 power-driven, rotatable, coaxial, horizontal spindles upon the inside ends of which are mounted abrasive disc wheels used for grinding 2 surfaces simultaneously.(12) "Horizontal single-spindle disc grinder" means a grinding machine carrying an abrasive disc wheel upon 1 or both ends of a power-driven, rotatable single horizontal spindle.(13) "Polishing and buffing wheels" means all power-driven rotatable wheels composed all or in part of textile fabrics, wood, felt, leather, paper, and may be coated with abrasives on the periphery of the wheel for purposes of polishing, buffing, and light grinding.(14) "Portable grinder" means any power-driven rotatable grinding, polishing, or buffing wheel mounted in such manner that it may be manually manipulated.(15) "Scratch-brush wheels" means all power-driven rotatable wheels made from wire or bristles and used for scratch cleaning and brushing purposes.(16) "Swing-frame grinder" means any power-driven rotatable grinding, polishing, or buffing wheel mounted in such a manner that the wheel with its supporting framework can be manipulated over stationary objects.(17) "Velocity pressure (vp)" means the kinetic pressure in the direction of flow necessary to cause a fluid at rest to flow at a given velocity. It is generally expressed in inches of water gauge.(18) "Vertical-spindle disc grinder" means a grinding machine having a vertical, rotatable power-driven spindle carrying a horizontal abrasive disc wheel.Mich. Admin. Code R. 325.52502