Detail Drawings

A detail drawing shows each part of a machine separately. The parts are completely dimensioned and enough views are drawn so that the machinist can make the piece without any other instructions. If necessary, notes are added to the drawing to make the fabrication of the piece clearer.

The details are sometimes drawn in the logical order that their visible on the machine. Adjacent parts in the machine are drawn adjacent to each other on the detail sheets. Sometimes the details of units that are to be created and possibly assembled in one part of the shop are grouped together on the detail sheets. In other cases, it may be just as well to group the details of similar parts that are to be made by the same machinist or department. In one group you may find all the details of the shafts required, another group all the gears, and still in another group all the gear guards, etc. The choice of any of these methods will be determined largely by the local conditions in manufacturing the machine.

fig5The image to the left shows the details of the crank end of a connecting rod. This is a simple bolted strap end that resists the tension of the rod by the shearing strength of the bolts and the friction set up between the stub end and the strap by the tightening of the bolts. It’s a very solid construction. Such open end type of construction is necessary on a center crank engine.

In assembling this end, the boxes are placed over the crank pin, the strap placed around the boxes, and the wedge secured in position by means of the cap screws. The stub end is next moved into position between the jaws of the strap, and is secured by the bolts.

Because of the heavy service this rod’s designed for, there’s not any allowance made for play between the boxes. The boxes are made of cast iron, babbitted, with flanges to prevent lateral movement. The babbitt, that forms the rubbing surface, is an anti-friction metal, sufficiently fusible to be melted in a common ladle. The use of this type metal is preferable because of its property of forming a perfect bearing without the need of re-boring. The boxes are held in position by a wedge that’s raised and lowered by means of two cap screws passing through the strap and tapped into the wedge.

If you wish to learn more about mechanical drawings, go to for more info.

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