TOOLS FOR THREAD ROLLING MACHINES

Nut taps GH class (thread limit) selection

class GH normal accuracy (13µm), class A increased accuracy (10µm).
Vertical Axis - Average Diameter Tolerance

The accuracy class of the nut tap is determined by the tolerances (1, 2, 3B, 2B etc.) on the internal thread

Table 1. Metric thread (M)

Table 2. American thread (U)

Table 3. W-Type thread

upper limit = 12.7 µm × n (n = GH number)
lower limit = upper limit - 12.7 µm

Example: GH limits GH6
upper limit: 12.7 × 6 = 77 µm,
lower limit: 77 µm - 12.7 µm (round to 13 µm) = 64 µm

Tapping Speed in different materials

Tapping speed formula for nut taps

V = π × D × N / 1000
π = 3,1416
V - cutting speed (m/min)
D - nut tap diameter (mm)
N - spindle speed (rpm)

Recommended Drill Hole Size for Nut Taps

Table 1. Metric Coarse Threads (M)

Table 2. Metric Fine Threads (MF)

Table 3. American UNC Thread

Table 4. American UNF thread

Table 5. W-Type thread

Tapping drill formula for nut taps:

Formula 1
drill size = D - 2 × H1 × (f1/100)
D - tap diameter
f1 = 90 ％ - percentage of thread engagement (in %)
H1 - thread height
H1 = 0.541266 × P
P - thread pitch

Formula 2
drill size = D - P
D - tap diameter
P - thread pitch