Taps are used for tapping internal threads. Common are metric threads or standard threads. There are also fine threads, trapezoidal threads, Whitworth threads and pipe threads, which differ in core diameter, pitch, flank diameter and the required core hole bore. For special threads, a special tool may be required, which can be made by specialized manufacturers on customer request. The drill for the core hole and the tap must be selected according to the thread.
Basic information on thread cutting
First, the core hole must be drilled with a drill. Then the core hole is countersunk with a countersink before the thread is cut. This can be done manually or mechanically. Depending on the material, cooling is carried out with emulsion or oil.
The following criteria are mainly decisive for the selection of the right threading tools:
manual or machine production
hard or soft material: steel, non-ferrous metal, plastics
high or low cutting speed
Drills and taps are available in high-speed steel (HSS) and solid carbide (VHM).
Manual one-off production
In small repair or training workshops, a CNC machine is not always available, so threads are cut by hand. Because of the low cutting speed of hand threading, high-speed steel (HSS) threading tools are often adequate. They are an inexpensive basic solution for workpieces made of steel, aluminum, copper and plastic. For hand tapping, a hand tap set with a pre-cutter, centre tap and finishing tap is recommended to reduce the cutting force.
For hard materials such as alloyed tempered steel or tool steel, threading tools made of solid carbide (VHM) are suitable. The advantages over tools made of HSS are the higher wear resistance of the cutting material and the shorter execution time due to up to three times higher cutting speed.
Machine series production
Machine taps made of solid carbide (VHM) are predominantly used in machine series production with CNC machines. These single-cut taps save a great deal of time because the thread is cut in the core hole in a single operation. Since only one tap needs to be clamped, set-up time is also reduced. In addition, a tap made of solid carbide allows higher cutting speeds compared to a tool made of HSS.
High precision and fast machining with coated taps
Coated machine taps are available in HSS and solid carbide. The coating allows a cutting speed twice that of the uncoated version. When machining non-ferrous metals, coated taps ensure maximum precision. The coating ensures a longer tool life at high cutting speeds and guarantees high-quality and economical production. Machine taps equipped with internal cooling provide additional process reliability and efficiency.
There are various tool holders for taps, depending on the machining machine. For manual tapping, the tap is clamped in a tap wrench. For tapping with a drilling machine, the use of a tapping attachment is recommended.
Manufacturers and wholesalers provide information about their product range and delivery conditions.