A pneumatic rotation grinder comprises a housing (10) with a throttle valve controlled air inlet passage, a rotation motor drivingly connected to an output shaft (12) intended to carry a grinding tool, a safety guard (17) adjustably supported on the housing (10) in a coaxial disposition relative to the output shaft (12), and a lock device (26-28, 33-38) for arresting the safety guard (17) in desired angular positions relative to the housing (10). The lock device (26-28, 33-38) comprises both a latch (26-28) for positive coupling by engagement of teeth (26, 28) of the safety guard (17) relative to the housing (10), and a pressure air activated clamping device (33-38) for frictional arresting of the safety guard (17) relative to the housing (10).

A shield for a dynamic cutting tool having a drive mechanism. A plurality of depressions are formed in a member surrounding the outer surface of the cutting tool mechanism or directly into the outer surface of the cutting tool mechanism. A flange member having a body portion at least partially surrounds the surface bearing the depressions and is movable relative to the same. A locking protuberance for selectively engaging any of the plurality depressions found on the accessible surface of the member is also provided and connects to the flange member.

A portable power tool for operating a wheel type grinding or cutting working implement comprises a housing (10), a rotating output spindle (11) with a working implement supporting flange (14), a safety guard (16) adjustably supported on a guide flange (15) on the housing (10), and a selectively operable arresting device (18) for positively engaging lock openings (20) on the safety guard (16) for locking the latter in alternative positions relative to the housing (10), wherein the support flange (14) is provided with a number of peripheral indentations (21), and the arresting device (18) comprises a lock bolt (19) which is longitudinally shiftable between a first position in which it engages either one of the lock openings (20) on the safety guard (16), a second position in which it engages either one of the lock openings (20) on the safety guard (16) as well as either one of the support flange (14) indentations (21), and a third position in which it neither engages anyone of the safety guard (16) lock openings (20) nor anyone of the support flange (14) indentations (21). A spring means (28, 29) is provided to bias the lock bolt (19) toward the first position.

A portable power grinder has a housing, a rotating output shaft with a grinding wheel mounting device, a grinding wheel safety guard adjustable between angular positions defined by apertures in the safety guard, and a manually operable safety guard arresting device engageable with an aperture. The arresting device has a lock slide movable on the housing and operable by an articulated lever connected at one end to the housing and at another end to the lock slide and being shifted by folding and unfolding, thereby moving the lock slide between a safety guard arresting position and a safety guard releasing position and locking the lock slide in the arresting position. The lock slide includes a spring exerting a force onto the safety guard in the arrested position. A lock spindle displaceably supported on the lock slide moves between a retracted safety guard locking position and an advanced position to lock the output shaft.

The invention proposes a grinder having a rocking shaft adapted to set a grinding tool into an oscillating movement about a rocking axis fixed to the device, the grinding tool having a grinding surface comprising at least one corner area. For the purpose of extracting the grinding dust, there is provided a suction hood, which can be fixed on the device and which communicates with a suction pipe. In order to prevent the risk of surface marks forming during micro-finishing of surfaces, and at the same time to guarantee efficient dust removal, the grinding surface is designed as a continuous, closed surface, without any openings, the suction hood enclosing the grinding tool from above and at least part of the lateral faces of the grinding tool. The suction pipe opens laterally into the suction hood in an area opposite the corner area of the grinding surface. Further, the suction hood comprises a suction chamber extending from the suction pipe to the corner area of the grinding tool.