A standard Cold Sprue Bushing  provides a means for the material to travel from the Machine Nozzle to the Primary Runner.

    The Nozzle end of the bushing has two important dimensions.
        1. There is a hole opening, it is referred to as the the "O" dimension, and the other is the spherical radius that seats with the nozzle.  The 'O' dimension should be 7/32R (.44 DIA) with 9/16R being used on very large molds. 
        2. The spherical radius should be .75 SPHR, or  .5 SPHR.

    The  hole inside the Sprue Bushing should tapered at .500 or .562 TPF.

    The taper hole diameter at the Runner end of the bushing  should be equal to, or be slightly larger than the runner diameter.  A radius of approx. .03-.06 should  be placed at the taper and runner intersection.

    Below the Sprue Bushing should be a provision for a Sprue Puller mechanism.  There are three common types of Sprue Pullers, and they are typically .25 below the parting line, which functions as a cold slug well. 
            Reverse taper well
             'Z' cut on Sprue Puller Pin
            Bulb machined on the end of the Sprue Puller Pin.

    Gussets are sometimes cut into the Sprue Bushing (sometimes gussets are machined into the B side too) to help reduce the cycle time.