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In manufacturing, a countersink (symbol: ⌵) is a conical hole cut into a manufactured object, or the cutter used to cut such a hole. A common use is to allow the head of a countersunk bolt , screw or rivet , when placed in the hole, to sit flush with or below the surface of the surrounding material (by comparison, a counterbore makes a flat ...
Comparison of countersunk and counterbored holes. Counterbore cutter marked 'E A counterbore hole is usually used when the head of a fastener, such as a hex head or socket head capscrew, is required to be flush with or below the level of a workpiece's surface.
At ground level beneath and around the headframe is the Shaft Collar (also called the Bank or Deck), which provides the foundation necessary to support the weight of the headframe and provides a means for workers, materials and services to enter and exit the shaft. Collars are usually massive reinforced concrete structures with more than one level.
Means that a feature of size is at the limit of its size tolerance in the direction that leaves the most material on the part. Thus an internal feature of size (e.g., a hole) at its smallest diameter, or an external feature of size (e.g., a flange) at its biggest thickness. The GD&T symbol for MMC is a circled M.
Engineering fits are generally used as part of geometric dimensioning and tolerancing when a part or assembly is designed. In engineering terms, the "fit" is the clearance between two mating parts, and the size of this clearance determines whether the parts can, at one end of the spectrum, move or rotate independently from each other or, at the other end, are temporarily or permanently joined.
Nominal (thread) sizes range from 0.1875 to 0.375 in (4.763 to 9.525 mm) and lengths from 1.25 to 5 in (32 to 127 mm). Typically an installer uses a hammer drill to make a pilot hole for each concrete screw and a powered impact driver to drive the screw. The drill hole should be 1/2" longer than the depth penetration of the screw.
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Example of true position geometric control defined by basic dimensions and datum features. Geometric dimensioning and tolerancing (GD&T) is a system for defining and communicating engineering tolerances via a symbolic language on engineering drawings and computer-generated 3D models that describes a physical object's nominal geometry and the permissible variation thereof.