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Standard Changes
The most obvious change to the standard was the division of the
standard into two parts as described in the introduction. Some
components of Part 1 also apply and are referred to in Part 2
and vice versa, so both parts must be considered together.
Major changes in part 1
Torque range
Section 5.1.3 specifies the torque range of the tool which is now
“the lowest marked value to 100% of the maximum torque
value.” Previously, tools were only calibrated to 20% of the
maximum torque value irrespective of the markings on the tool.
There was a risk that operators were using the tool in an
unknown state of compliance below 20%.
Application of torque
Section 6.2.1 states that the connection between the torque
measurement system and torque tool shall permit self-alignment
so that parasitic forces and moments are minimised.
This is a change from the previous version whereby torque tools
had to be mounted at 90° (± 3°) to the torque measuring device.
This introduced side loads - parasitic forces - which influenced
the torque measurement.
Major changes in part 2
In addition to the uncertainty of measurement of the
calibration system, the new standard also takes into
account the uncertainty of the torque tool itself.
Section 6.1 specifies the additional measurements to
be performed which in addition to repeatability
6.2.2 Variation due to the reproducibility of the
torque tool
6.2.3 Variation due to the interface between the
torque tool and the calibration system
6.2.3.2 Variation due to geometric effects of the
output drive of the torque tool
6.2.3.3 Variation due to geometric effects of the
interface between the output drive of the torque tool
and the calibration system
6.2.4 Variation due to the variation of the force
loading point
The standard does state that values can be determined
statistically with a sufficient number of specimens - at
least 10 - or through the manufacturer or 3rd party data
so long as care is taken to ensure validation.
Section 6.2.4 introduces a varying time limitation for the applied
torque to reach the target value (from 80% of target), dependant
on the target torque value. It is important to note that for torque
screwdriver calibration a maximum time is also specified (1.0 s).
This results in a 0.5 s window in which to reach the target value
(from 80% of target) and presents a significant difficulty when
using a manual loading device.
Section 8: The method described in part 1 is very similar to the
previous version. However, the requirement for 'certificate of
calibration' has been removed and replaced with a requirement
in section 8 for a 'declaration of conformance' to ISO 6789-
1:2017.
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