When starting a tap, it is helpful to have a relatively rigid assembly. This helps get the tap started in the hole and begin cutting threads. If the tapping system allows too much “push float”, or compression, when entering the hole, the tap will spin-out creating a mess of the threads at the top of the hole. Some compression is helpful since when the tap enters the hole forces try to push the tap out of the hole and slow the spindle rotation (physics, again!). A little compression allows these forces to do their work, while providing time for the feed-rate and spindle rotation to catch back up and get in lock step with each other. The MicroFLOAT system offers 0.008” of compression to help get taps started, but not enough to allow the tap to spin before it starts cutting threads.
Even though the discrepancy between the machine synchronization and the tap pitch is very small, the forces exerted on the tap with a solid holder are high. Measuring the thrust forces shows that a solid holder can exert 84 times greater axial forces on the tap than when using a microfloat tap holder doing exactly the same rigid tapping operation.
At the bottom of a tapping cycle, the MicroFLOAT system provides 0.040” of tension or “pull float”. As described earlier, the spindle rotation and feed-rate cannot stop and reverse to the necessary rates instantaneously. The MicroFLOAT system provides enough tension to allow time for the spindle rotation and feed-rate to decelerate, reverse, and accelerate to the required parameters on the way out. This mitigates the forces on the tap at the bottom and though the exit of the tapping cycle and results in improved thread quality, extended thread life, and fewer broken taps.
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