Pitch accuracy

Standards indicate a determined pitch accuracy measured on specified actual length. Values refer to measurements taken at an ambient temperature of 20°C. The 4 essential values  (V_300p, V_2pp, e_p, V_up)  which determine pitch accuracy are given in the tables below (in compliance with ISO 3408-3 standards).

CLASSE ISO - ISO CLASSE

1

3

5

7

V_300p (mm)

0,012

0,023

0,052

V_2pp (mm)

0,006

0,008

0,010

l_u (mm)

e_p

V_up

e_p

V_up

e_p

V_up

0÷315

0,006

0,006

0,012

0,012

0,023

0,023

315 ¸ 400

0,007

0,006

0,013

0,012

0,025

0,025

400 ¸ 500 

0,008

0,007

0,015

0,013

0,027

0,026

500 ¸ 630

0,009

0,007

0,016

0,014

0,030

0,029

630 ¸ 800

0,010

0,008

0,018

0,016

0,035

0,031

800 ¸ 1000

0,011

0,009

0,021

0,017

0,040

0,035

1000 ¸ 1250

0,013

0,010

0,024

0,019

0,046

0,039

1250 ¸ 1600

0,015

0,011

0,029

0,022

0,054

0,044

1600 ¸ 2000

0,018

0,013

0,035

0,025

0,065

0,051

2000 ¸ 2500

0,022

0,015

0,041

0,029

 0,077

0,059

2500 ¸ 3150

0,026

0,017

0,050

0,034

0,093

0,069

3150 ¸ 4000

0,032

0,021

0,062

0,041

0,115

0,082

4000 ¸ 5000

 -

 -

0,076

0,049

0,140

0,099

5000 ¸ 6300

 -

 -

-

-

0,170

0,119

Measurement symbols

l

 Threaded length.

l₀

 Nominal length.

l_u

 Actual length (on which measurements have to be carried out).

l_e

 Over-run (threaded length not subject to prescribed precision).

c

Any variation (usually negative) of specified actual length to compensate for the predictable lengthening caused by temperature increase or action of significant axial loads.

e_p

 Field of tolerance relative to average deviation of specified threaded length.

e_oa

 Total deviation of nominal threaded length.

e_sa

 Total deviation of specified threaded length.

V_up

 Maximum admissible deviation of pitch on actual length l_u.

V_ua

 Maximum real deviation of pitch on actual length l_u.

V_300p

 Maximum admissible deviation of pitch over a 300 mm tract.

V_300a

 Maximum real deviation of pitch over a 300 mm tract.

V_2pp

 Maximum admissible deviation of pitch referred to one turn of screw.

V_2pa

 Maximum real deviation of pitch referred to one turn of screw.

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