Общий каталог Yamawa 2022 - 2023 - страница 1159

Tapping Torque Tapping Torque

■Comparison of Cutting Torque by Different Type of Taps ○Tapping Torque Equation for Forming Taps

Cutting torque of hand tap (HT), and spiral fluted tap (SP), and spiral pointed tap (PO) differs, shown in the chart below. Based on the tensile strength of workpiece material, we prepare following equation to obtain tapping torque of standard forming taps. Condition : Effective length of internal screw is 1.5D. Thread height is 75%. Tapping Condition

Workpiece material : S50C Hole condition : 20mm through hole

If the cutting torque of hand tap is assumed as 100, the cutting torque of other taps is as follows :

Hand Tap : 100 Spiral fluted Tap : 70~75 Spiral Pointed Tap : 60~65

HT (plug) SP (2.5 threads) PO (5 threads)

■Tapping Torque of Forming type Taps

■Calculation for Tapping Torque of Roll Taps

○It is hard to calculate tapping torque for roll taps because they contain more complicated factor than the cutting taps. ○According to our experience, tapping torque of roll taps is twice or three times larger than that of the cutting taps in general. ○Major factors increasing or decreasing tapping torque of roll taps are : (1) Mechanical characteristic of workpiece (Tensile strength, hardness, spring back feature, work hardening index) : As the tensile strength gets larger, the threading torque becomes larger. (2) Size and length of bored hole: Bored hole size is usually defined to obtain 75% thread height of basic thread profile. Roll taps may be shuttered due to the excessive tapping torque when the bored hole size is made smaller to obtain higher thread height. Tapping torque gets larger as the efficient length of internal screw becomes longer because there is an increase in friction coefficient caused by spring back of workpiece material. (3) Tapping process (tapping speed, lubricant, and rigidity of main spindle). (4) Surface treatment of taps (oxidizing, nitriding, TiN, and TiCN coatings).

Technical Inf