| arc |
A curved feature representing a portion of a circle. |
| auxiliary view |
A view drawn at a right angle to an angled feature of the part. Auxiliary views show the true size of an angled surface. |
| blind hole |
A hole that is closed at its bottom. |
| blueprint |
A document containing all the instructions necessary to manufacture and inspect a part. The key sections of a blueprint are the drawing, dimensions, and notes. |
| bolt hole pattern |
A number of holes with centers that are positioned around the circumference of an imaginary circle. |
| bore gage |
A hole inspection gage that makes three points of contact within the hole. Bore gages are handheld, variable instruments that provide very accurate readings of hole sizes. |
| boss |
A raised, circular peg or protrusion. A boss often has a hole in the center and is used to improve assembly. |
| burr |
A rough, sharp edge remaining on a part after machining or stamping. Burrs pose an injury risk and interfere with the fitting of parts. |
| casting |
A part formed by pouring molten metal into a mold until it cools and solidifies into its final shape. Castings tend to have rougher surface textures. |
| center |
For circles and arcs, it is the point that is equally distant from all other points located on the circle's circumference or the arc. |
| center line |
A line used to define the center of a hole, a cylindrical part, or symmetrical part. Center lines consist of alternating long and short dashes. |
| chamfer |
A small, angled surface added on the end of a shaft, around the opening of a hole, or along an edge. A chamfer removes the sharp edge and helps remove burrs. |
| corner radius |
A rounded internal corner located where two features meet on either a flat or cylindrical part. |
| counterbore |
A larger diameter added at a hole opening, with a flat surface between the two diameters. A counterbore provides a space for the head of a bolt or other type of fastener. |
| countersink |
An enlarged, angled surface added to a hole opening. A countersink differs from a counterbore because it leaves a tapered opening. |
| deburring |
The removal of burrs on a part by processes such as grinding or filing. |
| degrees |
A common unit of measurement used to indicate the size of an angle. |
| diameter |
The distance from one edge of a circle to the opposite edge that passes through the center. Round or cylindrical features require diameter measurements. |
| fillet |
A rounded internal corner. A fillet adds strength to the corner and is often easier to machine. |
| go gage |
A gage on or in which a good part should fit easily. |
| hidden line |
A line used to define a part feature that is not visible in a specific view. Hidden lines consist of a series of short dashes. |
| ID thread |
A thread located on the interior surface of a cylindrical hole. |
| knurl |
A patterned series of grooves or diamond-shaped marks formed into the part surface. A knurl is added to provide a surface for gripping. |
| machining |
The process of removing metal to form or finish a part, either with traditional methods like turning, drilling, milling, and grinding, or with less traditional methods that use electricity, heat, or chemical reaction. |
| microinches |
One-millionth (.000001) of the U.S. standard inch. Surface roughness is typically measured in microinches. |
| neck |
A groove or smaller-diameter section between two larger diameters on a cylindrical part. A neck allows a flush or tight fit between the largest diameter and another part. |
| no-go gage |
A gage on or in which a good part should not fit. |
| nose radius |
The rounded tip on the cutting edge of a single-point tool. The nose radius on a tool leaves a matching corner radius on a part. |
| OD thread |
A thread located on the exterior surface of a cylindrical part or feature. |
| optical comparator |
An inspection instrument that projects a magnified shadow of a part feature onto a screen for measurement. |
| pictorial method |
A blueprint method of specifying a thread by attempting to represent the actual two-dimensional appearance of the thread. |
| pin gage |
A hardened, cylindrical gage used to inspect the size of a hole. Pin gages are available in standard diameters. |
| pocket |
An enclosed recess, often in a rectangular part. Most pockets are square or rectangular with rounded corners. |
| profilometer |
An inspection device that uses a stylus to trace along the surface of a part and determine its average roughness. |
| radius |
The distance from the center to the edge of a circle or arc. The size of a radius determines the size of the circle or arc. |
| radius gage |
A handheld gage with an accurate, rounded corner used to inspect the size of a corner radius on a part. Radius gages are available in a set that offers a range of sizes. |
| roughness |
The inherent, fine, closely spaced irregularities remaining on a part surface after manufacturing. |
| schematic method |
A blueprint method of specifying a thread by showing a series of parallel lines. |
| section line |
A line used to identify the imaginary cut portion of a part in a section view. Section lines appear as a series of diagonal lines drawn close together. |
| section view |
A view illustrating a rotated section resulting from an imaginary cut in the part. Blueprints may contain a variety of different section views. |
| simplified method |
A blueprint method of specifying a thread by including pairs of solid and dashed lines drawn parallel to the thread. The simplified method is the most common method for specifying a thread. |
| spotface |
A shallow, larger diameter added at the top of a hole. A spotface is most often used on castings to provide a flat surface for assembly. |
| stylus |
A small, cone-shaped spherical point made of diamond that contacts the part and measures surface roughness. |
| surface finish |
The degree of smoothness of a part's surface after it has been manufactured. Surface finish is the result of the surface roughness, waviness, and flaws remaining on the part. |
| taper |
For a cylindrical part, it is a gradual decrease in diameter from one end to another. For a flat or rectangular part, it is an angled surface that gradually changes from a larger height to a smaller height at a constant slope or incline. |
| thread |
A raised, helical rib or ridge around the interior or exterior of a cylindrically shaped object. Threads are found on screws, nuts, and bolts and are used to fit parts or provide motion. |
| thread class |
A number and letter combination that indicates the degree of fit for a thread. |
| thread form |
The specific shape or profile of a thread. Thread forms include V-shaped or square threads. |
| thread ring gage |
A disk of heavy metal with a central, threaded hole made to match a particular OD thread. The gage is screwed onto the part being inspected as though the two are mating parts. |
| thread series |
A thread designation that identifies the coarseness or fineness of a thread. |
| THRU |
A hole that passes completely through a part's material. |
| Unified thread system |
A standard thread form based on inches that was developed by the U.S., Canada, and Great Britain. |