Definition of sprue

A: Sprue is pronounced as it is written with a silent ‘e.’ The word is actually used more in the casting industry than in the forging industry. In forging, it describes the enlarged opening (half round per die) at the flash line where the escaping metal flows more freely than from the normal flash gap. Since it is thicker than typical flash, it prevents sagging when the hammer or press operator lifts the part from the blocker die to the finisher die. Sprues are especially useful when producing elongated forgings in platters that tend to sag between impressions. While use of sprues does tend to cost more in the way of metal losses, (3-5% more), they eliminate much of the sag and problems with mislocation. Sprues also aid in production because the operator can locate the parts easier. Operators usually appreciate the use of sprues that stiffen the tong-hold region. That was part of the problem discussed in the earlier article on mislocated parts.

For more than 40 years H. James Henning held key technical positions in the forging industry, including as director of technology for the Forging Industry Association, and as president of Henning Education Services, a Columbus, OH, firm specializing in customized education and training in forging technologies.

Guidelines and recommendations offered in this column are based on information believed to be reliable and are supplied in good faith but without guarantee. Operational conditions that exist in individual plants and facilities vary widely. Users of this information should adapt it, and always exercise independent discretion in establishing plant or facility operating practice.