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Guide to Thread Forming Taps (Roll Taps)

Thread Forming Taps are the tools used for producing internal threads by a thread forming process. Currently, YAMAWA's Thread Forming Taps have

P1 P3 P5 a good reputation by being used in many areas. They are widely used along with the diversity of workpieces and with the change into miniaturization

P2 P4 P6 of workpieces. Followings are the characteristics and features of Thread Forming Taps (Roll Tap) which are not available with cutting taps.

210220230240
<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
P1time for chip disposal.
№2-56UNC53 70
GH2Roll taps are stronger than cutting taps due to their design. The effect of fluteless design gives a large cross-section area to the tap,
P1and there is no worry of chip jamming, which makes Roll taps very tough against breakage.
№3-48UNC55 75Roll taps produce excellent pitch diameter well within pitch diameter tolerances. Material deformation process produces the
GH2internal threads with good surface finish as well as precise pitch diameter.

P1 P2 P3 High efficiency and tool life The configuration of the lobes at the crests of the tap threads makes high speed tapping possible and extends

№4-40UNC60 83tool life compared with cutting type taps. The addition of a supplemental tap surface treatment, such as Oxidizing, Nitriding, TiN, and TiCN can
GH2 GH3 GH4 GH5extend tool life 2 to 20 times over an uncoated (bright) tap performance.
P1
№5-40UNC63 83<Points to note during a Roll tapping operation>

GH2 ○ Tapping torque is 2 to 3 times larger than that of cutting type taps. ○Roll tapping is only applicable to materials producing stringy chips. ○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.

P2P4P6
○The selection of lubricants is important to prevent sticking or welding.
P3P5P7○
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.
210220230240
○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.

P2 P3 P4

№6-32 UNC6893<Selection of YAMAWA Roll Taps>
GH2 GH3 GH4 GH5 GH6 GH7
Types of Roll Taps YAMAWA produces various types of Roll Taps which include General purpose taps, Special purpose taps for non-ferrous and

P2 P3 P4 steel, as well as special purpose taps with surface treatment for the specified applications. To provide for longer tool life, specially developed

№8-32 UNC71 96
GH2 GH3 GH4 GH5 GH6 GH7premium materials are also used together with physical vapor coating deposition (PVD) such as TiN and TiCN. In particular, OL-RZ is superior
product developed for dry machining with regards to tapping environment and performance.

P2 P3 P4 Tap Materials

№10-24 UNC 80 108 YAMAWA's standard tap material is SKH58 designed for improving torque, superior anti-friction properties as well as toughness.

GH3GH5 GH6 GH7To extend tool life, we use SKH56, or SKH10(Powder HSS) which is the best tap material for antifriction.
P2Tolerance 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.
№12-24 UNC82 110The differences in materials being Roll tapped, as well as hole size, contribute to differences in thread forming. YAMAWA offers 2 to 3 oversized tap
GH3tolerance classes in order to achieve the most suitable internal thread pitch diameter size.

P2 P3 P4 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

1/4-20 UNC 90 123 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

GH3 GH5 GH6 GH7 in a few words because each different tapping condition influences the tool life.

P2 P3 P4

5/16-18 UNC 98 134 <Shape of internal threads and the ratio of thread engagement affected by bored hole diameter>

GH3GH5GH7Compared with the basic height of thread engagement, the actual height of the thread engagement is called "thread engagement ratio" in percentage.
P2P3P4Depending on the bored hole diameter, internal threads and thread engagement ratio will change.

3/8-16 UNC 108 144

GH3GH5GH7In tapping, the tapping condition must be chosen by referring to the thread engagemet ratio.
P2P3The portion of material to be formed can be reduced by selecting the largest possible bored hole diameter. In this way the load on tap is reduced,
7/16-14 UNC116 154decreasing tap’s wear and damage.
GH3GH5

P2 P3 P4 S50C, minor diameter of threads cut Aluminum, minor diameter of threads formed

1/2-13 UNC 121 165

GH3 GH5 GH7 M24x3 M25x2

P2 minor dia tolerance of internal threads minor dia tolerance of internal threads

9/16-12 UNC 128 172

GH3 20.752~ 21.252 22.835~ 23.210

P3 P4 Internal External Aluminum, internal threads formed Internal External

5/8-11 UNC 136 182 S50C internal threads cut

GH3GH5threadsthreadsM25x2threadsthread
M24x3
bored hole size : 23.903side

P3 P4 bored hole size : 20.652

3/4-10 UNC144 195minor diameter of finished internal threads : 22.723mm
minor dia tolerance of internal threads NG
GH3GH5minor dia tolerance of internal threads NG
thread engagement ratio : 103.1%
P3thread engagement ratio : 105.2%

7/8-9 UNC 154 207

GH4 Aluminum, internal threads formed S50C internal threads cut M25x2 M24x3

bored hole size : 24.042mm bored hole size : 21.000 minor diameter of finished internal threads : 23.067mm minor dia tolerance of internal threads: Middle

P2P4P6P8minor dia tolerance of internal threads : Middle
thread engagement ratio : 92.4%
thread engagement ratio : 89.3%
P3P5P7⑤
⑤Aluminum, internal threads formed
S50C internal threads cut
210220230240M25x2
M24x3
bored hole size : 24.240mm
bored hole size : 21.352
P4minor diameter of finished internal threads : 23.462mm

1-8 UNC 167 223 minor dia tolerance of internal threads NG

minor dia tolerance of internal threads NG GH4 thread engagement ratio : 81.5% thread engagement ratio : 71.0%