Multiple-pass broaching (i.e. two-pass, three-pass broaching) simply refers to the number of times a separate operation must be performed on a part to accomplish the desired shape and size.
Sometimes the length of cut required on a part is too long to be accommodated by the passing of one broach alone. In that case two or more broaches are pulled or pushed through or past the part, each one cutting progressively more to the finished size. In other cases a particularly smooth finish is required on the part, and a ‘finishing broach’ is used after the part is cut largely to the required specifications.
In still other cases, multiple dimensions are cut on a single piece, requiring the part to be indexed or turned in some fashion, before either the same broach or a different broach is used to cut the additional dimension.