9ANSI Hole Identification Symbols DiameterCounterbore / SpotfaceCountersinkDepthNumber of holes
10Drill Holes - Size & Location Dimensions Always add dimensions for size and location, to profile of featureAlways locate a drill hole by a common corner.(Datum Corner)
11Dimensioning Repeated Holes X = Number of holes required.Don’t forget to provide a space
12Blind HoleDepth SymbolA blind hole cuts into but does not pass completely through the object.For blind holes always show a 30 degree bevel end to represent the drilling process.
13Counterbore CalloutsDepthSymbolCounterbore SymbolCounterbore – To enlarge the end of a drill hole to a specific diameter and depth in order to recess a mating part.
14Through HolesA through hole is one that passes all the way through the object.The word THRU may be omitted in the annotation of the hole.
15Spotface CalloutsCounterboreSymbolSpotface – The cutting of a shallow counterbore, usually about deep (depth symbol is omitted). A spotface provides an accurate bearing surface for the underside of a bolt head.
16Countersink CalloutsCountersinkSymbolAngle of The ChamferDrawn At90 DegreesCountersink – To recess a hole with a conically (cone) shaped tool to provide a seat for flat head screws. (Does not need a depth to be specified.)
18KnurlingCommon on thumbscrews and handles of to provide a better gripping surfaceStraight – parallel groves.Diamond – crossing diagonal groves.
19Knurling Dimensioning AsSeenThe callouts for a knurl should include the pitch, type, and the diameter.AsDrawnThe most commonly used diametrical pitches (DP) are 64 DP (coarse), 96 DP (medium), 128 DP (fine), and 160 DP (extra fine).
24Fillets & RoundsSharp corners are weak. They are likely to yield cracks and other failures in the part.Fillets – are rounded inside corners.Rounds – are rounded outside corners.
25Fillets and rounds are normally found on cast, forged, or plastic parts. Rough Cast
26RunoutsConventional methods for representing fillets and rounds
27Conventional EdgesIf an edge has a small radius, a line should be shown.If an edge has a large radius, no line should be shown.Draw lines for edges whenever such lines make the drawing clearer.No Line
29Surface Texture Symbols Finish MarksTells the machinist which surfaces are to be finished or machined.
30ANSI Standard Finish Mark (now in general use)H = Standard Letter Height For General Notes.
31Rules About Finish Marks Shown on the edge view of a surface to be finished.The vertex of the finish mark should point inward toward the solid metal.Position to read from the bottom of the sheet or from the right side of the sheet.
32Rules About Finish Marks It is repeated in every view where the surface appears asa line, including hidden lines and curved lines.Machined Casting
33Rules About Finish Marks Finish marks are not required for drill holes or any other holes where machining operations are clearly illustrated.
34Rules About Finish Marks If a part is to be finished all over, omit the finish marks.Letter as a general note on the drawing, such as FINISH ALL OVER or FAO.General noteShould be placed near the title blockNOTES:FINISH ALL OVER.FILLETS AND ROUNDS R.125.BREAK SHARP EDGES.