Threads and Fasteners

Fasteners

FastenersStandard Bolts and Nuts:

American National Standard bolts and nuts, both inches and metric, are produced in hexagon form.

Square head bolts and nuts are only produced in the inch series.

Square bolts and nuts, hexagon bolts, and hexagon flat nuts are unfinished. Unfinished bolts and nuts are not machined on any surface except for the threads.

Finished bolts and nuts are characterized by a “washer face” machined on the bearing surface.

The washer face is 1/64” thick but drawn at 1/32”. The diameter is equal to 1 ½ times the body diameter.

Fasteners

Bolt Proportions:

Regular hexagon and square bolts and nuts:

W = 1 1/2D

H = 2/3D

T = 7/8D

Thread Lengths:

For bolts up to 6” in length: Thread length = 2D + ¼”

For bolts over 6” in length: Thread length = 2D + ½”

Fasteners

Drawing Standard Bolts:

Bolt heads and nuts should be drawn across corners in all views regardless of projection to prevent confusion between the square and hexagon heads and nuts.

Only when there is a special reason should bolts heads and nuts be drawn across flats.

In such cases, the conventional proportions are used as shown.

FastenersSteps in drawing a finished hexagon head bolt and hexagon nut.

FastenersSteps in drawing a square-head bold and square nut:

FastenersStandard Cap Screws:

FastenersStandard Machine Screws:

FastenersKeys are used to prevent relative movement between shafts and wheels, couplings, cranks, and similar machine parts attached to or supported by shafts.

A woodruff key is semicircular in shape. The key fits into a semicircular key slot cut with a Woodruff cutter as shown, and the top of the key fits into a plain rectangular keyway (figure c).

FastenersMachine Pins:

Machine pins include taper pins, straight pins, dowel pins, clevis pins and cotter pins.

The taper pin is effective for fastening hubs or collars to shafts.