The Punch Tap

New Punch Tap Tool Quickly Forms Helical Threads

Tool targeted at auto industry puts threads in aluminum and other soft metals.

A few years ago, engineers and management at Emuge Corp., a leading maker of taps, drills, and other rotary tools, decided it needed a new tool for forming helical threads in lightweight metals and aluminum used in the automotive industry. Like all good engineers, they wanted the tool to work faster and use less energy. To make sure the designers had the users’ perspective, Emuge partnered with Auidi AG, a company known for high-quality cars and consumer vehicles. Recently Emuge introduced its patented Punch Tap Line in North America.

The taps are made from a tough, long-wearing HSSE-PM alloy with teeth shaped to create threads in a single step. It has two rows of flutes offset 180 deg. from each other and extending in a helical curve down to the usable application depth. This design gives it a tool path about 1/15th of that made by traditional cold-forming taps when making an M6 thread with a 15-mm depth. The shortened tool path lets the threading forming take less than half a second. This leads to significantly less energy consumption during machining and reducing threading times by 75%.

The Punch Tap from Emuge Corp. created threads in a single, quick, helical motion.

Prior to the threading operation, the tool punches into a pre-drilled hole; the first tooth of each flute generates a helical groove that helps guide the tap to the application depth. Once the tap reaches that depth, threads are cold formed by a synchronous movement of feed and rotation. The thread has a half left-turn in the pitch, and each tooth produces half a thread (approximately 180 deg.). After the threads have been formed, the tap is retracted in a helical movement from the hole via the grooves. The finished threads are interrupted by two helical grooves offset by 180 deg.

Thread strength is comparable to conventionally machined threads with thread depths of twice the hole diameter. The Punch Taps are sized and engineered for specific coatings and dimensions and are available by special order. They can be used in blind and through-holes with metric threads ranging from M3 thru M10 (inch sizes are also available from #8 thru 5/16). To keep the fast working tap cool, it can have an internal coolant supply capability using emulsion or minimum quantity lubrication (MQL). The taps are used on CNC machines programmed with a specialized punch tap cycle, available from machine tool and control unit manufacturers. Machine parameters, such as acceleration, will require adjustment for some applications.

Click here to see the Punch Tap in action.

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