CAT-SET

THREADING

Thread Mill CalculaƟons and Recommended Passes

Thread Mill Drill CalculaƟon Based on nominal tap drill diameter. Based on 0.075 mm (0.003") probable mean oversize.

Major Thread Diameter for # Drills Drill # Thread Diameter # 2 0.086 # 3 0.099 # 4 0.112 # 5 0.125 # 6 0.132 # 8 0.164 # 10 0.190 # 12 0.216

To calculate the percent of full thread for a given hole diameter:

Basic major diameter of thread - Drill hole size 0.0130

IMPERIAL: % of thread = # of threads per inch •

76.96 Pitch (mm)

METRIC:

• [ Basic major diameter of thread - Drill hole size ]

% of thread =

Recommended Passes

NPT / NPTF / BSPT / API

Recommen ISO ded Passes

UN / UNJ / BSPP / BSW / NPS / NPSF Pitch Size Machinability Easy Average Difficult 64 1 1 2 56 1 1 2 48 1 1 2 44 1 1 2 40 1 1 2 36 1 1 2 32 1 1 2 28 1 1 2 24 1 1 2 20 1 2 3 19 1 2 3 18 1 2 3 16 1 2 3 14 1 2 3 13 1 2 3 12 1 2 3 11 2 2 4 10 2 3 4 9 2 3 4 8 2 3 4 7 2 3 4 6 2 3 4

Machinability

Machinability

Pitch Size

Pitch Size 0.40 0.45 0.50 0.70 0.75 0.80 1.00 1.25 1.50 1.75 2.00 2.50 3.00 3.50 4.00 4.50 5.00 6.00

Easy

Average Difficult

Easy

Average Difficult

28 27 19 18 14 11 10

1 1 1 1 1 1 1 1 2

1 1 1 1 2 2 2 2 3

2 2 2 2 3 3 3 3 4

1 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2

1 1 1 1 1 1 1 2 2 2 2 3 3 3 3 3 3 3

2 2 2 2 2 2 2 3 3 3 3 4 4 4 4 4 4 4

11.5

8

1 Pass 2 Passes 3 Passes 4 Passes

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