There is a relatively rare broaching technique available for complex metalworking shapes. Blind broaching is a method of broaching that can cut into parts where the cut may not be visible due to the shape of the piece. This method involves creating indents and shapes into metalwork pieces without going through the other side of the material. This method of broaching is only done by the most skilled broaches due to the degree of difficulty in the blind broaching process.
Blind broaching may not be the only broaching process that requires careful machining but it is the only process that requires a set-up that only goes partway through the piece. In other words, it makes an indent or slot into the workpiece. There are not many applications that require broached blind holes, but for some metal parts it is the only method that can produce them. A sample of industries that may require the use of blind broaching include construction and aerospace industries.
Although very similar to internal broaching, blind broaching is considered a surface broaching process, because the broach does not completely go through the workpiece. The process itself usually involves a series of short push broaches. A series of broaches are placed on a circular indexing table that rotates either under or over the workpiece. Each broach is sequentially larger than the preceding tool. During this process the workpiece is pushed onto the broach to remove material from the external surface of the piece.
The blind broaching process is an efficient and economical way of making internal splines. Sometimes referred to as blind-hole broaching, this method is utilized to cut slots, colds and imprints that are hexagonal, square, round or splines in parts.