Taps and Dies

In tapping and reaming operations, it is not a good idea to force a cutting tool to move in any particular direction.

This is not a problem when the previously drilled hole lines up exactly with the machine spindle centerline, but that is not always the case. One way to ensure that tools faithfully follow the drilled path is to use taps and dies that have radial float.

These devices let taps and dies "drift" to accurately position themselves at the center of the designed target area, even when misaligned. By compensating for any misalignment before tapping or reaming, shops get a better surface finish and eliminate wear on tools and machines.

In tapping, a holder that provides radial float accurately produces a high-quality thread with good tap tool life. The floating action also eliminates any angularity of the tap to the centerline of the spindle, preventing binding of the taps and dies.

The same benefits exist for reaming operations that use radial-float taps and dies. In reaming, tools sometimes are guided to the hole by bushing plates that may or may not be aligned with the spindle centerline. This can cause rubbing or binding of the reamer through the bushing. The floating holder compensates for this misalignment.

In reaming applications in which no bushing plate is used, the holder must allow the reamer to find the center of the hole. Otherwise shops will end up with bell mouthing of the hole-diameter entrance. Without a radial float, the reamer has to engage a sufficient amount of the hole before it stabilizes in the cut. If the reamer does not stabilize, an oversized or out-of-round hole results.

Floating taps and dies are usually found on high-production transfer lines, dial or rotary-index machines and tapping machines that only tap previously drilled holes. These taps and dies can also be used to tap castings that have as-cast holes, which are not qualified by additional drilling on the same machine on which the tapping takes place.

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