D = diam. of shaft, 21⁄2 inches.
L = length of bearing, 33⁄4 inches.
T = thickness of collar, 7⁄8 inch.
d = diam. of collar, 31⁄2 inches.
Generally it is preferable to give the diameters of turned and bored work on a section, instead of an end drawn separately; confusion is sometimes caused by a number of radial dimensions.
[Fig. 242 and fig. 243] are introduced to show the principal measurements required in practical work, and the usual way in which such dimensions are marked when ordering parts of machinery.
[Fig. 242] is a pedestal, or metal frame; three views are shown, the center figure being an elevation, the lower figure is the plan of the base, the upper figure is a view of the top, on which is bolted the bearing block, it being on the outside of the center figure. The essential measurements are marked by letters. H is the vertical height from base to the seat of bearing block: L being the length, and W the width of the base; P is the length between checks, and B the width of seat for bearing block; C is the distance from center to center of the holding down bolt holes, and T is the depth of the holes in the base; K is the distance from center to center of the bolt holes in the top for bearing block.
[Fig. 243] is a hanger, or metal bracket, and shows the center figure or elevation, the plan of the top and the plan of the seat for bearing block, which is bolted on the interior of the center figure. H is the vertical distance from the top to the seat for bearing block; the other measurements required are marked by letters similar to [figure 242].
Now, one of the important matters in connection with dimensioning a drawing is the location of the figures. One rule, whose utility cannot be gainsaid, is that they should be so located that they can be altered or erased without damage to the lines of the drawing, as changes may be necessitated either by original errors in writing down the figures or by changes in the design being found desirable during the construction of the machine.
Fig. 243.—Fig. 244.