Tap and die

A tap is a drill to generate thread -bearing holes in various materials. Tapping counts according to DIN 8580 as -machined hole drilling processes to main-group separation. Also known are the designations of the drill nut and Digger. The former originates from the shape of the created thread, is reminiscent of the second amount of feed which is set by the thread pitch. The appropriate tool for cutting external threads, the cutting iron.

Appearance and function

Depending on the size has a tap two or more cutting edges. The blades have teeth that wear of the material to be processed per a chip. The teeth at the tip of the tap differ strongly flattened ( control). This increases during cutting of each tooth has a chip approximately the same width. The teeth further back the leadership of the tap are only in the already cut part of the thread. At the rear of hand taps have a square head, with which they can be mounted in a holder, the tap wrench.

Variants

The most common are Machine Taps (for use by hand or machine ) or Machine tap, as well as three-piece Hand Taps Sets. Hand Tap Sets consist of spurs, a plug tap and bottoming tap. The pre- labeled with a ring on the shaft, the central cutter with two rings. The bottoming tap is not wearing a ring, or ( rarely) three rings.

Machine Taps offer the advantage that the cutting is faster. However, they are usually only suitable for through holes, there is not sponsored clean outward in blind holes of the chip. In addition, they break in the processing of harder steels from very easy because a wider tension is removed than with three-piece sets and thus a larger torque is needed. For blind holes taps are needed with spiral grooves that lead to tension against the cutting direction of the hole.

Hand Taps are usually made ​​of high speed steel (HSS ).

Application

For cutting an internal thread, a core hole is drilled first, the diameter of which is smaller by approximately the slope than the nominal diameter of the thread. For example, is at a standard thread M10 with a thread pitch of 1.5 mm, a blind hole with a diameter of 10 mm - are manufactured 1.5 mm = 8.5 mm. Then to get when cutting a better introduction into the hole and to prevent the first and the last thread are pushed out, introduced dimples that correspond to the size of the thread diameter plus 10% of this. With an M10 thread, the 10 1 mm, that is a reduction of 11 mm in diameter. And in turn the three - - Then will tap into and unscrewed again. Through additional plastic deformation of the threads here arises the final core hole diameter is 8.38mm for M10.

To increase the tool life and optimum surface quality cutting oils or other cooling lubricants are used for lubrication, because that reduces the friction between the chip and the cutting edges of the tap, and thus the necessary torque.

The tap should not be turned back as possible while cutting because frequent shearing of chips and Neuanschneiden cause premature dulling of the Taps cutting. Exception: For long-chipping materials and bigger threads repeated breaking of the chips is required. This is done by turning the tap at approximately 1/ 4 turn. At the same time thereby enters fresh lubricant to the cutting edges.

In particular, for threads which are not substantially longer than its diameter, the thread cutting by hand easily be inclined. In contrast, usually only helps machine cutting or manually rotating the spindle of a pillar drill with clamped Taps. Standardized small and medium-sized internal thread can be easy and inexpensive to manufacture on the lathe by means of taps at rotationally symmetrical workpieces.

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