Tapping heads or tap holders are responsible for holding taps that create threads in a hole. They are mounted on the spindle of an automatic drill press through a threaded shank. These come in two configurations – reversing and non-reversing tapping heads. Reversing or self-reversing tapping heads automatically back up and thread up to a predetermined depth. For non-reversing heads, you need to manually stop the press and reverse the head when the tap has reached its required depth. They are less convenient and more time-consuming.
Self-reversing tapping heads are increasingly popular for their efficiency. They make batch production easier without compromising on accuracy. They have a ball-clutch mechanism that prevents or reduces breakage and rubber flex collets that work at variable speeds.
Working with a metal that requires multiple taps requires you to have an automatic drilling machine capable of multiple tapping. A multiple spindle head offers a simple, straightforward solution applicable in industrial settings or high productivity workshops. These dual-spindle heads are available with typical vertical milling machines or drill presses and attach to the head nearly as quickly as regular spindles. They have the self-reversing feature, reducing interruptions and increasing output.
This setup is ideal because it allows pre-drilling and successive tapping of many parts quickly and reliably using a consistent thread pitch. You can also use self-feeding taps to save time spent centering your workpieces.
Modest threading jobs do not necessarily require an automated drilling machine. You can tap by hand or on a drill press using a tap drill.
For straighter, more accurate tasks, you need the additional torque that only a drill press can provide. Place your tap on a tap driver or in the chuck. After centering the drill point, use a low initial speed to start the tap and after the cut is sufficiently deep, reverse the spindle clutch to back the tap out. A state-of-the-art driller gives you control over the force and rotation speed to prevent damaging your taps. As the tap ejects, keep light pressure to preserve the two or three threads already formed.
You can switch out your tap or increase the speed. It would be best to be mindful of the rotational force applied to your taps as they are fragile and easily ruined. Factors that determine the cutting speed include:
- The nature of the material being tapped
- The depth of the hole
- The pitch of the thread
- The rigidity of your driller
- The tapping fluid
- The length of the chamfer
There are machining calculations that you can do when you want mathematical correctness. However, there are a few universal rules to follow. Lower cutting speeds with increasing depth to allow for chip evacuation. Intermittently apply cutting fluids or use an automatic fluid apply method and use low speeds for bottoming taps. Lower speeds are desirable when cutting many threads or very fine ones.
Get acquainted with your integrated auto driller to wield total control over its movements and speeds. It will prevent tap breakage as all variables in the cutting process will be in your control.
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