# 3 Wire Pitch Dia. Method - Measuring Force Correction & Lechowski?s method

S

#### sgopal

3 Wire Pitch Dia. Method - Measuring Force Correction & Lechowski’s method

Hi I am new here
My question is regarding correct method to apply compression correction in 3-wire method of determining pitch dia.
European co-operation for accredition document EA-10/10 describes method for Correction for the deformation of the spherical probing elements
approximated as a ball-on-flat contact with Hertz’ formula which can be used for compression correction for internal thread measurement by three wire method where spherical ball is used.
This document does not specify method to arrive at deformation of cylindrical wires used external thread measurement by 3-wire method.
Qmsys Thread PD programme says that "The correction for the measuring force is defined by Lechowski’s methods". Inspite of extensive GOOGLING i am unable to find any reference this method.
I find internal thread compression correction results tally with results calculated based on method described in EA-10/10 document for spherical balls.But for external threads the correction is 45 % of internal thread correction
NPL gives compression correction=constant*force^(2/3)/pitchdia^(1/3) with constants specified for different thread forms. It also gives correction chart.
My questions are
1. What is the correct method for applying compression correction.
2. What is formula for Lechowski’s method

#### harry

Super Moderator
Re: 3 Wire Pitch Dia. Method - Measuring Force Correction & Lechowski’s method

Welcome to the Cove.

Qmsys is related to one of our Regular Poster. Be patient and wait for him to check-in (this is a weekend and usually very quiet).

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