A dental handpiece (1) having a drive (3) of a tool (4), which drive is located in a head housing (2), has at least one media-conducting line arranged in the head housing, which media-conducting line has an outlet opening to the tool, and a tool receptacle (16) arranged in a drive chamber, which tool receptacle is rotatably supported by means of a rolling bearing (11) in a support (14) of the head housing (2) on a side of the drive chamber facing the tool. The rolling bearing has an outer race (13), which is supported against the head housing (2) radially in the support (14) in the area of a raceway (22) and which has a sub-area (21), the outside diameter D2 of which is reduced compared to the outside diameter D1 in the area of the raceway (22). The head housing has a housing projection (23), which extends into the area of the reduced outside diameter D2, and the media-conducting line (17) runs at least partially through said housing projection (23).

When the compressed air is not applied, an inclined surface, which is positioned at an upstream side with respect to the supply direction of the compressed air, of the lip part is in contact with the inclined surface of the inner ring. When the compressed air is applied, a contact area between the inclined surface, which is positioned at the upstream side with respect to the supply direction of the compressed air, of the lip part and the inclined surface of the inner ring becomes smaller, as compared to when the compressed air is not applied.

The rolling bearing includes: an outer ring having an outer ring raceway surface on an inner peripheral surface; an inner ring having an inner ring raceway surface on an outer peripheral surface; rolling elements rotatably arranged between the outer ring raceway surface and the inner ring raceway surface; and a seal member that is fixed to a seal attachment groove formed in an axially end portion of the outer ring by a snap ring and seals an axially end portion of a bearing internal space between the outer ring and the inner ring, in which an outer diameter of the seal member is larger than an outer diameter of the snap ring in the seal attachment groove, and in which a radially outer end portion of the seal member is sandwiched between an inner peripheral surface of the seal attachment groove and an outer peripheral surface of the snap ring.

A ball bearing includes an inner ring; an outer ring placed outside of the inner ring; a plurality of rolling bodies intervening between the inner ring and the outer ring; and an annular cage including pockets rotatably holding the rolling bodies in a circumferential direction at intervals determining a rotation axis to be a center. The cage comprises a resin composition comprising a polyetherketone-based resin, graphite, and a carbon fiber. The resin composition comprises the polyetherketone-based resin in an amount of 60% by weight or more and 80% by weight or less, the graphite in an amount of 10% by weight or more and 30% by weight or less, and the carbon fiber in an amount of 5% by weight or more and 20% by weight or less when the entire resin composition is determined to be 100% by weight.

A martensitic stainless steel containing, by mass %, C: 0.20% to 0.40%, N: 0.1% or less, Mo: 3% or less, and Cr: 12.0% to 16.0%, such that 0.3%C+N0.4% and a PI value (=Cr+3.3Mo+16N) is 18 or more, with the remainder being substantially Fe and unavoidable impurities is quenched from a temperature of 1,030 C. to 1,140 C. and subjected to a subzero treatment and tempering so as to obtain a prior austenite crystal grain size of a surface layer of 30 m to 100 m and a surface hardness of 58 HRc to 62 HRc.

A rolling bearing includes an outer ring, an inner ring, a plurality of rolling bodies, and a seal member. An outer peripheral portion of the seal member is fixed by a retaining ring to a groove portion formed on an inner peripheral surface of the outer ring and an inner peripheral portion of the seal member is elastically deformable. The seal member includes an inclined portion. 1?Ts/Sct?10 is satisfied when Ts is a circumferential gap of the retaining ring at a time when the seal member and the retaining ring are attached to the groove portion of the outer ring and Sct is an axial thickness of a part of the seal member in contact with the retaining ring.

A rolling bearing includes an outer ring, an inner ring, a plurality of rolling bodies, and a seal member. An outer peripheral portion of the seal member is fixed by a retaining ring to a groove portion formed on an inner peripheral surface of the outer ring and an inner peripheral portion of the seal member is elastically deformable. The seal member includes an inclined portion. The seal member satisfies 0.25?Skn/Skt?2.5 when Skn is a radial length from an inclination start part of the inclined portion on an inside in an axial direction to an outermost diameter position of a part of contact of the seal member with an outer peripheral surface of the inner ring and Skt is a thickness of the inclined portion in a direction perpendicular to an inclination direction.

The present invention relates to a dental and/or surgical instrument (1) comprising a motor that drives a tool by way of a tool holder (24, 25, 27) situated in the head of the dental and/or surgical instrument (1), the tool holder (24, 25, 27) being supported in the head of the dental and/or surgical instrument (1) by at least a first ball bearing (21) and a second ball bearing (22), in which the first ball bearing (21) and the second ball bearing (22) are positioned in a cartridge (10) which is inserted into the head of the dental and/or surgical instrument (1), and in which the cartridge (10) comprises a single bore (80) for the mounting and guiding of both the first ball bearing (21) and the second ball bearing (22). The present invention additionally relates to a cartridge (10) to be inserted into the head of such a dental and/or surgical instrument.

A martensitic stainless steel containing, by mass %, C: 0.20% to 0.40%, N: 0.1% or less, Mo: 3% or less, and Cr: 12.0% to 16.0%, such that 0.3%C+N0.4% and a PI value (=Cr+3.3 Mo+16 N) is 18 or more, with the remainder being substantially Fe and unavoidable impurities is quenched from a temperature of 1,030 C. to 1,140 C. and subjected to a subzero treatment and tempering so as to obtain a prior austenite crystal grain size of a surface layer of 30 m to 100 m and a surface hardness of 58 HRc to 62 HRc.

A dental hand piece or angle piece including a rotating tool, which is driven via a rotating drive element disposed in a housing, wherein the rotating drive element is mounted in the housing by a radial rolling bearing, wherein the rolling bearing comprises an axial abutment surface and the housing comprises an axial countersurface, and wherein the rolling bearing is axially preloaded with respect to the housing by a spring element 11 and has a coefficient of friction for the static friction of the abutment surface to the countersurface or the abutment surface and the countersurface to the spring element that is at least 0.16 in the lubricated state and at least 0.25 in the unlubricated state.