Dimensioning and Tolerancing Chapter 10 continued Dimensioning and Tolerancing

General Notes Relate to the entire part or drawing as a whole Located next to the title block Notes: Material specs Units General tolerances Finish specs Etc.

Delta Notes Refer to a specific area of the part Note is numbered (usually located with general notes by title block)

Local Notes Applied to a specific area of the part by a leader All text on drawings to be capitol letters

Dimensioning Systems The manner of which dimensions are applied to drawings for different applications. Selected based on: How the part will be manufactured What features of the part are important based on its function How many features are on the part The general shape of the part Systems can be combined to better dimension relationships of features

Unidirectional Dimensioning all text is horizontal and read from the bottom of the sheet.

Aligned Dimensioning all text is aligned with the dimension lines Horizontal dimensions are read from the bottom Vertical dimensions are read from the right side

Rectangular Coordinate Dimensioning (10.61) Dimensioning linear dimensions to locate features from planes, centerlines and center planes

Arrowless Dimensioning (fig 10.14) Also called Ordinate and Rectangular Coordinate without Dimension Lines Dimensions shown as extension lines only Horizontal and vertical dimensions measured from common locations (origin labeled as 0.00) Size dimensions for holes given in a table

Tabular Dimensioning (fig 10.15) Size and locations given as x, y, z coordinates Dimensions shown in a table Features to be shown in table are labeled with letters

Chart Drawing (fig 10.16) Multiple parts dimensioned on one drawing Dims common to all parts are placed on the drawing, dims that differ are placed in a table Used for parts that have the same shape but different dimensions Differences between parts can be dimensional or something as minor as a color difference Cuts down on the number of drawings Also used in catalogs for ordering parts

Chain Dimensioning (fig 10.24) Also called point to point Dimensions from one feature to the next Causes tolerance buildup

Datum Dimensioning (not in book) Each dimension is measured from a common edge Very commonly used on engineering drawings Commonly combined with chain dimensioning

Polar Coordinate Dimensioning (10.62) Use of angular dimensions to locate feature Typically on round parts

Dimensioning Symmetrical Objects Part must be completely symmetrical about a centerline Can show entire view or partial view Must show symmetry symbol on centerline

Dimensioning Features Angular Surfaces Can be dimensioned by: Dims at both end of the angled surface Dim at one end and angular dim Flat taper note

Chamfers Chamfer-a slight surface angle to relieve sharp corners or create lead in on a part that will be inserted into a hole. 45 ˚ chamfers can be dimensioned with a note 3X45˚ or 3X3 All other angles require normal dimensioning

Conical Taper Dimensioning a cylindrical object that changes diameter Dimensioned in a view where it appears as a triangle