Quy chuẩn về dạng đá mài

(Theo ANSI B7.1-2010)

Quy chuẩn này đưa ra các định nghĩa cho các dạng đá mài và các giới hạn về hình dáng, kích thước của chúng. Sau đay là nguyên văn theo ANSI B7.1-2010. 

The following wheel shape definitions and limitations are safety standard recommendations for general use and should be used wherever possible. Wheel dimensions or shapes differing from the standard recommendations below may be used on specific machines but shall require the approval of the wheel and machine manufacturer.

- Abrasive disc wheels Definition: A grinding disc or cylinder type disc used in single or double disc surface grinders, with a shape similar to a Type 1 straight wheel or a Type 2 cylinder wheel. The entire circular, flat side, opposite the mounting surface, is used for grinding

a. Anchor mounted discs These discs are mounted with bolts or screws to a machine supporting plate by several means such as, but not limited to, imbedded nuts and washers in the back of the disc.

b. Plate mounted discs These discs are mounted to a machine supporting plate by a cemented-on steel backplate having tapped holes and/or projecting studs or other means for mounting.1.4.2 Corner clearance ('C' dimension) The corner clearance is defined as the junction between the inner wall of a recess and the flat ('K' Dimension).

- Recess diameter ('P' dimension) The recess diameter is defined as: P = K + (2 x C)

- Type 1 straight wheels 

Definition: Type 1 straight wheels have diameter, thickness and hole size dimensions and grinding should be performed on the periphery. This does not preclude their use for applications such as shoulder contour and form grinding where it is recognized that a limited amount of side grinding will be performed. Extreme caution should be exercised not to use excessive side pressure.

Limitation: Hole dimension (H) should not be greater than two-thirds of the full size wheel diameter dimension (D) for precision, cylindrical, centerless or surface grinding applications. Maximum hole size for all other applications should not exceed one-half the wheel diameter. Inorganic wheels used in snagging operations should have a maximum hole size of not more than one-quarter of the wheel diameter.

- Type 2 cylinder wheels

Definition: Type 2 cylinder wheels have diameter, wheel thickness and rim thickness dimensions. Grinding shall be performed on the rim surface only, dimension W. Cylinder wheels may be plain, plate mounted, inserted nut or of the projecting stud type.

Limitation: Rim height, T dimension, is equal to or greater than rim thickness, W dimension. 

- Type 5 recessed one side wheels 

Definition: Type 5 recessed one side wheels have diameter, thickness and hole size dimensions and in addition also have recess diameter and depth dimensions.

Limitation: Type 5 wheels are subject to the same limitations of hole size, use and mounting as Type 1 wheels, definition above. In addition, recess depth, F dimension, should not exceed 50% of wheel thickness, T dimension. The inside flat K dimension, shall be large enough to accommodate a suitable flange.

- Type 6 straight cup wheels

Definition: Type 6 cup wheels have diameter, thickness, hole size, rim thickness and back thickness dimensions. Grinding should be performed on rim surface, W dimension.

Limitation: Minimum back thickness, E dimension, should not be less than 1/4 T dimension. In addition, when unthreaded hole wheels are specified, the inside flat, K dimension, shall be large enough to accommodate a suitable flange.

-Type 11 flaring cup wheels

Definition: Type 11 flaring cup wheels have double diameter dimensions D and J, and in addition, have thickness, hole size, rim and back thickness dimensions. Grinding should be performed on rim (grinding) surface, W dimension.

Limitation: Type 11 wheels are subject to all limitations of use and mounting listed for Type 6 straight sided cup wheels. Minimum back thickness, E dimension, should not be less than 1/4 T dimension. In addition, when unthreaded hole wheels are specified, the inside flat, K dimension, shall be large enough to accommodate a suitable flange. 

- Type 12 dish wheels

Definition: Type 12 dish wheels have diameter, thickness, rim thickness and back thickness dimension. In addition, Type 12 wheels always have a surface thickness, U dimension. Grinding may be performed on both A and U dimensions.

Limitation: Minimum back thickness, E dimension, should be equal to or greater than 1/2 wheel thickness, T dimension, J and K dimensions shall be large enough to accommodate a suitable flange. 

- Type 13 saucer wheels

Definition: Type 13 saucer wheels have diameter, thickness, hole size and back thickness dimensions. Grinding shall be performed on wheel periphery, U dimensions, only.

Limitation: J and K dimensions shall be large enough to accommodate suitable flanges. In addition, wheel thickness shall always equal E dimension.

- Types 16, 17, 18, 18R and 19 cone and plug wheels 

Definition: Type 16 cones have a curved side with a nose radius. Type 17 cones have straight sides with or without a nose radius. Type 18 and 18R plug wheels are cylindrical in shape with either a square or curved grinding end. Type 19 cone wheels are a combination of cone and plug type shapes and are usually specified where base dimension D in a Type 17 cone would not provide an adequate cross section of abrasive. All types of cone and plug wheels are manufactured with blind hole threaded bushings and may be used on all surfaces except the flat mounting surface D.

Limitation: Cone and plug type wheels are mounted by being screwed onto a threaded machine spindle so that surface D seats firmly against an unrelieved, flat back-up flange.The maximum volume of type 16 through 19 cones and plugs shall not be greater than 35 cubic inches (example: a 3″ diameter, 5″ thick (T) type 18 plug wheel). Also, the thickness shall not be less than the base diameter. (Example: a 2″ diameter wheel shall not be less than 2″ thick.)

Exception: Valve seat wheels, where the mounting spindle is an integral part of the pilot used to align the wheel with the valve seat surface during grinding, need not be mounted as described above.

- Types 20, 21, 22, 23, 24, 25, 26 relieved and/or recessed wheels

Definition: Types 20 through 26 relieved and/or recessed wheels have diameter, thickness, hole size, recess diameter and depth dimensions, and in addition may have tapered relief on one or both sides.

Limitation: Types 20 through 26 wheels are subject to the same limitations of use and mounting as Type 1 wheels. Tapered relief depths shall be considered as recesses and added to straight recess depth or depths for determination of total wheel recess depth. Total recess depths should not exceed 50% of wheel thickness, T dimension. Dimension K shall be large enough to accommodate a suitable flange.

- Types 27 and 28 depressed center wheels

Definition: Types 27 and 28, depressed center wheels, have diameter, thickness and hole size dimensions. Both types are reinforced, organic bonded wheels having depressed centers which permit grinding without interference with the mounting. Type 27 wheels are manufactured with flat grinding rims or faces and are designed for side grinding, when used at a slight angle to the workpiece, or peripheral grinding, including small cutting-off and shallow notching operations. When grinding masonry and concrete surfaces, such as ceilings and walls, they may be used flat. Such wheels have deeper than normal depressed centers for flat blending. Type 28 wheels have saucer-shaped grinding rims and are designed for corner grinding and side grinding, and shall not be used for cuttingoff or notching operations.

Limitation: Special supporting, back adaptor and inside flange nuts are required for the proper mounting of these types of wheels. Mounts which are affixed to the wheel by the manufacturer may not require an inside nut and shall not be reused. It is the user/owner's responsibility to ensure wheels with this type mount fit inside the guard.

-Type 27 abrasive flap disc wheels Construction consists of a reinforced organic bonded wheel shape with a depressed center metal reinforced arbor hole. Grinding portion consists of abrasive coated cloth pieces which are layered and glued on the peripheral portion of the bottom side. Common shapes have flat and tapered layered coated abrasive grinding surfaces.

- Type 27A depressed center wheels

Definition: Type 27A depressed center, cutting-off wheels have diameter, thickness and hole size dimensions. They are reinforced, organic bonded, offset hub type wheels, usually 16″ diameter and larger, specially designed for use on cutting-off machines where mounting nut or outer flange interference cannot be tolerated.

-Type 29 wheels

Definition: Type 29 grinding wheels have reversed saucer shaped grinding rims and are designed for blending (stock removal which leaves a smooth finish). They shall not be used for cutting off or notching applications.

- Cutting-off wheels

Definition: Cutting-off wheels have diameter, thickness, and hole size dimensions. They may be metal or organic bonded abrasives of the non-reinforced, reinforced, heavily reinforced or metal center type.

(a) Non-reinforced cutting-off wheels are designed to withstand only centrifugal, radial and tangential cutting forces in the plane of the wheel.

(b) Reinforced cutting-off wheels are strong in the plane of the wheel and are better able to withstand some lateral and twisting forces.

(c) Heavily reinforced wheels have greater amounts of reinforcement than category (b) and are intended for use on heavy duty, high speed applications where the cutting plane is not fixed.

(d) Metal centered wheels may be used on any of the aforementioned cutting-off operations.

Limitation: Cutting-off wheels are subject to all limitations of mounting and use listed for Type 1 wheels. In addition, cutting-off wheels are recommended only for use on specially designed and guarded machines and are subject to the following maximum thickness and hole size limitations.

Wheel Diameter                  MaximumThickness

4″ and Smaller                                    1/8″

Larger than 4″ to 6″                           3/16″

Larger than 6″ to 12″                         1/4″

Larger than 12″ to 23″                       3/8″

Larger than 23″ to 48″                       1/2″

Larger than 48″                                  5/8'

Maximum hole size for cutting-off wheels should not be larger than 1/4 wheel diameter 

- Mounted wheels

Definition: Mounted wheels, usually 2″ diameter or smaller, and of various shapes, may be either organic or inorganic bonded abrasive wheels. They are secured to plain or threaded mandrels.

- Threaded hole cup wheels

Definition: Threaded hole cup wheels Types 6 and 11 are designed for use on vertical, right angle head, or flexible shaft portable grinders. They have one central threaded bushing, securely anchored in place. They are mounted by being screwed onto a threaded machine spindle so that the wheel back seats firmly against an unrelieved flat back flange.

Limitation: Threaded hole cup wheel mounting should not be used with wheels larger than 6″ diameter for portable applications. However, it is recognized that some swing frame applications do require larger than 6″ diameter threaded hole cup wheels. Back flanges used in mounting threaded hole cup wheels shall be flat and unrelieved. Grinding should be performed on the grinding surface only.

-Tuck pointing wheels

Definition: Tuck pointing wheels are Type 1 reinforced organic bonded wheels and have diameter, thickness and hole size dimensions. 

Limitation: Tuck pointing wheels are subject to the same limitations of use and mounting as Type 1 wheels.

- Modified Types 6 and 11 wheels (terrazzo)

Definition: Some Types 6 and 11 cup wheels used in the terrazzo trade have tapered K dimensions to match a special tapered flange furnished by the machine builder.

Limitation: These wheels shall be mounted only with a special tapered flange.

 

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