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ALLIED MACHINE & ENGINEERING | RECOMMENDED CUTTING DATA

Thread Mill Calculations and Recommended Passes

Thread Mill Drill Calculation Based on nominal tap drill diameter. Based on 0.003" or 0.075 mm probable mean oversize.

Major Thread Diameter for # Drills Drill #

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

Thread Diameter

# 2 # 3 # 4 # 5 # 6 # 8

0.086 0.099 0.112 0.125 0.132 0.164 0.190 0.216

Basic major diameter of thread - Drill hole size 0.0130

% of thread = # of threads per inch •

IMPERIAL:

76.96 Pitch (mm)

% of thread =

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

METRIC:

# 10 # 12

Recommended Passes

NPT / NPTF / BSPT / API

Recommen ISO ded Passes

UN / UNJ / BSPP / BSW / NPS / NPSF

Machinability

Machinability

Machinability

Pitch Size

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

Easy

Average Difficult

64 56 48 44 40 36 32 28 24 20 19 18 16 14 13 12 11 10

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

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

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

28 27 19 18 14

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

11 10

8

1 Pass 2 Passes 3 Passes 4 Passes

9 8 7 6

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