Thread Forming Taps are the tools used for producing internal threads by a thread forming process. Currently, YAMAWA's Thread
Forming Taps have a good reputation by being used in large area. They are widely used along with the diversity of workpieces and with
the change into miniaturization of workpieces. Followings are the characteristics and features of Thread Forming Taps (Roll Tap) which
cutting type taps do not have.
<Features of Roll Taps>
Tapping without producing chips. They are suitable for blind hole tapping. In producing internal threads with no chips, they save you a
time for chip disposal.
Roll taps are stronger than cutting taps due to their design. The effect of fluteless design gives a large cross-section area to the tap,
and there is no worry of chip jamming, which makes Roll taps very tough against breakage.
Roll taps produce excellent pitch diameter well within pitch diameter tolerances. Material deformation process produces the
internal threads with good surface finish as well as precise pitch diameter.
High eciency and tool life The configuration of the lobes at the crests of the tap threads makes high speed tapping possible and extends
tool life compared with cutting type taps. The addition of a supplemental tap surface treatment, such as Oxidizing, Nitriding, TiN, and TiCN can
extend tool life 2 to 20 times over an uncoated (bright) tap performance.
<Points to note during a Roll tapping operation>
Tapping torque is 2 to 3 times larger than that of cutting type taps.
Roll tapping is only applicable to stringy materials.
The deviation of hole size before tapping should be about 5% of pitch. The control of hole size before tapping should be more severe than that of
cutting type taps.
The selection of lubricants is important to prevent sticking or welding.
Burrs at the face of an internal thread are larger than those produced by cutting type taps. In some cases it is necessary to take additional counter-
sink processing at the top of hole.
In the minor diameter of internal thread, U-shape form (Tine form) at the hole entrance can be seen. U-shape form is never seen when using cutting
type taps.
<Selection of YAMAWA Roll Taps>
Types of Roll Taps YAMAWA produces various types of Roll Taps which include General purpose taps, Special purpose taps for non-ferrous and
steel, as well as special purpose taps with surface treatment for the specified applications. To provide for longer tool life, specially developed
premium materials are also used together with physical vapor deposition (PVD) such as TiN and TiCN. In particular, OL-RZ is superior product
developed for dry machining with good regards to tapping environment and performance.
Tap Materials YAMAWA's standard tap material is SKH58 designed for improving torque, superior anti-friction properties as well as toughness.
To extend tool life, we use SKH56, or SKH10(Powder HSS) which is the best tap material for antifriction.
Tolerance Class Using the datum 12.7μm in a step form, in accordance with ANSI standard GH class, we made up YAMAWA's G class system.
The differences in materials being Roll tapped, as well as hole size, contribute to differences in thread forming. YAMAWA offers 2 to 3 oversized tap
tolerance classes in order to achieve the most suitable internal thread pitch diameter size.
Chamfer length Chamfer lengths : 2 pitches for blind hole use and 4 pitches for through hole use. Basically 4 pitches have longer tool life than
2 pitches because force applied on one blade at 4 pitch chamfer is smaller than that at 2 pitch chamfer. However, it is difficult to say about tool life
in a few words because each different tapping condition influences the tool life.
<Shape of internal threads and the ratio of thread engagement aected by bored hole diameter>
Compared with the basic height of thread engagement, the actual height of the thread engagement is called "thread engagement ratio" in percentage.
Depending on the bored hole diameter internal threads and thread engagement ratio will change
Introduction to Thread Forming Taps (Roll Taps)
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