A-A-51140 Chucks, Drill, Key Type, Three-Jaw, GearedThis commercial item description CID establishes the government acquisition requirements for geared three-jaw drill chucks capable of being adjusted to hold any size straight shank tool within the capacity of the chuck. The jaws of the chuck shall be opened and closed by means of a pinion-type key.

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A-A-51140B

2.2 Type II. Threaded-mount

Style A - medium duty chucks - intended for use on stationary and portable power tools.

Size - see table I

Style B - heavy duty chucks - suitable for use with heavy-duty portable power tools.

Size - see table II

3. SALIENT CHARACTERISTICS

3.1 Material. The chuck body shall be constructed of carbon steel or tool steel. All chuck jaws shall be made of alloy steel. Chuck keys shall be made of cold rolled steel or equivalent.

3.2 Hardness. The sides of the key holes shall be hardened to not less than 48 on the Rockwell "C" scale when measured in accordance with the American Society for Testing and Materials (ASTM) E 18, "Standard Test Methods for Rockwell Hardness and Rockwell Superficial Hardness of Metallic Materials" (DoD adopted). The gripping surface of each chuck jaw shall have a hardness of not less than 52 and each

chuck key shall be hardened on the bearing surface and shank to a value of not less than 42 on the Rockwell

"C" scale when measured in accordance with ASTM E 18.

3.3 Tapered-mount hole chuck. The tapered-mount hole of type 1 chucks shall conform to the requirements of table I, II, or III for the chuck size specified.

3.4 Threaded-mount hole chuck. The threaded-mount hole of type 2 chucks shall conform to the dimensions of tables I or II for the chuck size specified. The threads shall conform to type 2B tolerance requirements of the American Society of Mechanical Engineers (ASME) Standard B1.1, "Unified Inch Screw Threads (UN and UNR Thread Form)" (DoD adopted). The direction of the threads shall be such that to remove the chuck from a tool spindle, the chuck must be turned in the same direction the spindle rotates when in use. Chucks designed for use on reversible tools shall have a retaining screw or other suitable means to secure the chuck during reverse operations.

3.5 Bearings. All style A and B drill chucks shall have plain bearings. Style C drill chucks shall contain ball thrust bearings. The ball thrust bearings shall be of a standard commercial quality, readily available for replacement purposes. If thrust bearings are not sealed-for-life, means shall be provided for lubrication.

3.6 Drill chuck capacity. The drill chuck shall conform to the drill holding capacity listed in the respective tables for the type and style chuck required.