Обший каталог Yamawa 2016 - 2017 - страница 781

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■ ■Tapping Torque of Cutting type Taps

The torque starts increasing as the threads of chamfer enter the workpiece material. It becomes highest when all threads of chamfer cut into workpiece material, and is in plateau until the chamfer cuts through the workpiece. After that, the torque will decrease until the end of tapping.

Tapping Torque Equation for Cutting Taps

Table 1 Specific cutting resistance of each material .

Tc = tanθ 24000 kc×K(D-Do)2 ×(D+2Do) Materials to be cut Specific cutting resistance kc N/mm²

Material symbolsHardnessN/mm²
Tc : Tapping Torque (N-m)5t44-2133HB3700
kc : Specific cutting resistance (N/mm2)Ck 15141HB3600
K :Correction coefficient depending on tap geometry and chipsCk 35162HB3700
Ck 45188HB3900

D : Nominal Diameter of Tap (mm)

Ck 60188HB4000
Do : Bored hole diameter (mm)42 CrMo 4193HB3600
θ :Thread half angle (° )30HRC4900

40HRC 5500

kc and K : Refer to Table 1 and Table 2X 6 CrNi 18 10209HB4200
C 105 W2175HB5300
CnZn40−2300
G-AISi8Cu3−1300
GG-25193HB2900

Table 2 Correction coefficient depending on each tap geometry Coefficient K Materials to be cut ・

Steel Cast iron Aluminum alloys Brass

Kinds of tapcoarsefinecoarsefinecoarsefine
Hand tap plug1.351.151.251.081.601.12
Hand tap bottoming1.431.501.301.251.68−
Spiral fluted tap1.151.251.051.100.85−
Spiral pointed tap0.951.000.801.000.751.00

■Cutting Torque Line

Cutting torque lines in the test of different kinds of taps, hand tap, spiral fluted tap, spiral pointed tap are shown below. Tapping Condition Tap : HSS P2 M8×1.25 Bored hole size : 6.8mm Cutting speed : 6.1m/min Cutting oil : Water insoluble oil Workpiece material : Ck60 Machine : Drilling machine Tapping type : 10mm Through hole Measurement equipment : Piezoelectric torque tester

Type of tap Torque lines Description

Hand tap (P2) Plug tap (5 threads) Plateau is observed since whole chamfer threads enter the workpiece material. Tapping time is much shorter than that of the taper tap.

Plateau is also observed since whole short Bottoming tap chamfer threads enter the workpiece material. (1.5 threads) Tapping process time is shorter than that of the plug tap. Spiral fluted tap (P2, 2.5 threads) Spiral fluted tap pulls out the chips, good choice for blind hole tapping. The cutting torque of spiral fluted taps is smaller than that of the hand taps. Spiral pointed tap (P2, 5 threads) Spiral pointed tap pushes out the chips forward. It is good choice for through hole use. Cutting torque is smallest in all taps.

The cutting torque will change depending on the kind of taps, cutting chamfer, number of flutes, workpiece materials and their hardness, lubrication types, and chips.