Общий каталог Tungaloy 2020 - 2021 - страница 1631

Shim replacement method o f ST- t y p e tools B

Compensation for the lead angle and tool relief angle

When the pitch is large or the screw diameter is small, the Thread angle Pitch P (large)

lead angle becomes large and the eff ective relief angle on the C

Pitch P (small) = lead advance flank side becomes small. In particular, this will Thread height 2 cause shorter life of the insert in the case of trapezoidal screw with small fl ank angle. It is ideal without any interference for the thread cutting insert to have an equal relief angle on both right and left. Replace the shim so that the rake face of insert faces Lead angle D

the thread groove direction (that is, = ). Flank (large)

3 Lead angle (small) Calculating the lead angle α The lead angle is calculated as follows: E

• : Lead angle

= tan-1 R/πd) = tan-1 nP/πd) R : Lead Shim Insert n : No. of threads θ P : Pitch Toolholder d : Pitch diameter

The relief angle is calculated as follows: Pitch compensation

1 diameter d 1

Insert Small clearance 90°-

• = tan (tanθ tanα) (Possibility of

1 -1 interference) 2

Shim G

The α of a standard toolholder is 10˚ for external threading

• I–I cross section

and 15˚ for internal threading.

ød (Pitch diameter)

πd Accordingly, the eff ective relief angle is calculated as follows:

• : Lead angle I

2 = 1 3 : Effective relief angle

2

• : Lead angle 3

compensation value In other words, = when the thread lead angle is equal to 1 2 the compensation value. Namely, the relief angle of the tool

itself is equal to the effective relief angle. If the wrong J

compensation value is used, > . The eff ective relief angle 1 2 becomes smaller and cause the interference between the

StandardStandard CompensatedCompensated StandardStandard CompensatedCompensated

±1˚ when the thread angle is 60˚ and 55˚ K ±30˚ when the thread angle is 30˚ and 29˚ Compensation of lead angle for shim less internal toolholders When using internal threading toolholders without shim, the above- shown below. The fi nal fi gure of the designation (-2 or -3) indicates 2°

mentioned method can not be applied for lead angle compensation. or 3° lead angle to be used respectively. The toolholders without L Therefore, special toolholders for large lead angles are available as these fi gures are for 1° lead angle.

M

1° 2° 3°

SNR0016M16 SNR0016M16-2 SNR0016M16-3