Metric, imperial, and American thread calculation formulas

Metric thread (MM tooth)

Tooth depth = 0.6495 * tooth pitch P (angle of teeth 60 degrees)

Internal tooth diameter = nominal diameter -1.0825*P

M20x2.5-6H/7g (right hand) - (single head thread) - (metric thick teeth)

(nominal diameter 20mm) (tooth pitch 2.5mm)

(internal thread matching level 6H)

(External thread matching level 7g)

Left-double head-M20x1.5 (left hand)-(double thread)-(metric fine teeth) (nominal diameter 20mm) (tooth pitch 1.5mm)

American thread

(unified standard thread)

Tooth depth = 0.6495* (25.4/number of teeth per tooth) (angle of teeth 60 degrees)

3/4-10UNC-2A (UNC coarse teeth) (UNF fine teeth)

(1A 2A 3A external tolerance tolerance level)

(1B 2B 3B internal tolerance tolerance level)

UNC US uniform standard coarse thread

OD 3/4 inch, 10 teeth per inch

External tooth level 2 tolerance

Pipe thread (Inch PT)

Tooth depth = 0.6403* (25.4/number of teeth per tooth)

(tooth angle 55 degrees)

PT 3/4-14 (tapered pipe thread) Taper pipe thread, taper ratio 1/16

3/4 inch tube, 14 teeth per inch

Thread

(PS straight thread) (PF fine teeth)

Tooth depth = 0.6403* (25.4/number of teeth per tooth)

(tooth angle 55 degrees)

PS 3/4-14 (straight pipe thread)

PF1 1/8-16 (straight pipe thread)

(fine teeth)

Straight pipe thread

3/4 inch tube, 14 teeth per inch

1 1/8 inch tube, 16 teeth per inch

Pipe thread (US NPT)

(fang angle 60 degrees)

NPT 3/4-14 (conical pipe thread) tapered pipe thread, taper ratio 1/16

3/4 inch tube, 14 teeth per inch

Trapezoidal thread

(30 degrees metric)

TM40*6 nominal diameter 40mm pitch 6.0mm

Trapezoidal thread

(29 degree Aikem thread)

TW26*5 OD 26mm, 5 teeth per inch

Square thread

Calculation of teeth

Consider the conditional formula

Conversion of metric and imperial teeth per thread n = 25.4 / pitch P

Pitch P = 25.4 / number of threads per thread n

Because of the workpiece material and the speed of rotation determined by the tool N = (1000 cycles speed V) / (pi) p * diameter D

Because of the speed determined by the machine structure

The rapid movement of the tool holder affects the maximum speed of the tooth N = 4000/ P

The effect of rapid movement acceleration and deceleration

Calculation of lower and retracted points

(calculation of incomplete teeth) minimum distance L1 of the lower knife

L1 = (tooth pitch P) * (spindle speed S) / 500

Retracting the maximum distance L2

L2 = (tooth pitch P) * (spindle speed S) / 2000

Tooth depth and bottom diameter d tooth depth h = 0.6495 * P

Root diameter d = nominal outer diameter D - 2 * h

Example: Car outer teeth 3/4"-10UNC 20mm long

Conversion distance between metric and imperial teeth P = 25.4 / (吋 thread number n)

P = 25.4 / 10 = 2.54mm

Due to the workpiece material and the speed determined by the tool, the outer diameter D = 3 / 4 inches = 25.4 * (3/4) = 19.05MM

Speed ​​N = (1000 cycles speed V) / (pi) p * diameter D)

N = 1000V / pD = 1000 * 120 / (3.1416*19.05)

=2005 rpm (rev / min)

Because of the rapid change of the speed of the knife seat determined by the machine structure, the maximum speed of the tooth is N = 4000 / P

N = 4000/2.54 = 1575 rpm

Integrated workpiece material tool and mechanical structure

The determined speed N = 1575 rpm

N = 2005 turn

The lower speed of the two choices, that is, 1575 rpm

The effect of rapid movement acceleration and deceleration

Calculation of lower and retracted points

(calculation of incomplete teeth) minimum distance L1 of the lower knife

L1 = (tooth pitch P) * (spindle speed S) / 500

L1 = 2.54*1575/500=8.00mm

Retracting minimum distance L2

L2 = (tooth pitch P) * (spindle speed S) / 2000

L2 = 2.54*1575/2000=2.00mm

Deep tooth and bottom diameter d Deep tooth diameter d = Nominal outer diameter D-2*h = 19.05-2*1.65 = 15.75mm

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