Known for being a universal and quick process, tapping is the process of making threads in previously drilled holes, and in most cases a tapped hole can be created faster than when using a thread mill. Tapping can generally thread deeper holes in harder materials and any type of machine—a lathe, mill, or drill press—can be used.
“The advantages of tapping are improving thread quality, cycle time and tap life,” said Mark Johnson, president of Tapmatic (Post Falls, ID). “If you can shorten cycle time, you are increasing production. Depending on the application, when using a self-reversing tapping attachment, customers can gain back weeks of production time per year.”
Taps need to be produced according to the application since there are many factors that influence the tap. “At Tapmatic we have seen high-volume jobs in automotive, where there are a lot of cast aluminum and cast iron applications. Also, customers are tapping more aerospace related materials, like Inconel and titanium.”
Tapping is the only process where the machine spindle must be stopped and reversed. When stopping and reversing, the machine slows down as it gets to bottom of the hole and the tap isn’t cutting at the optimum speed. “With a self-reversing tapping attachment, there is no deceleration since you are not stopping the machine, and the self-reversing attachment eliminates the start and stop, which is easier on the machine because it takes more energy to stop the machine and start it up again,” said Johnson.
Tapmatic’s specialty is producing a variety of tapping attachments and tap holders for different applications. “With the tapping attachment, you feed in and retract—when you retract it automatically reverses the tap to bring it back out. If you have a workpiece with a lot of the same sized holes, you can have a big impact in reducing cycle time by using a self-reversing tapping attachment.”
Tapmatic makes tap holders for synchronized tapping on CNC machines, which typically come with a synchronized tapping cycle. The tap holders also provide micro compensation. “Even though the cycle is accurate, there is always a slight discrepancy between the machine synchronization and pitch of the tap,” said Johnson. “If you have a solid tap holder that puts a lot of extra thrust force on the tap, it tends to wear it out more quickly. You can have a dramatic effect on thread quality by using the right kind of tap holder [the tap holder of choice depends on the application] or tapping attachment. When tapping on a machine with a synchronized tapping cycle it is better to use a holder like the SynchroFlex design, which has a small amount of tension-compression float, allowing the tap to follow its proper pitch.”
Another thread quality factor is tap lubrication. “We provide tapping attachments and holders where the machine reverses both attachments and holders for high-pressure internal coolant, providing lubrication, cooling, and evacuating chips,” said Johnson. “Also, no time is lost changing the tap frequently, and money is saved by not having to replace the cutting tool and tap so often.”