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SATRA’s whole sole flexing machine

Highlighting the value of the SATRA STM 465 test machine, used to assess an outsole’s ability to resist cut growth during flexing.

by David Billington

Poor design, the selection of inferior materials or inadequate methods of construction can result in soles that are vulnerable to fatigue cracking due to the repeated flexing induced when walking. To assess the risk of such component breakdown, SATRA produces a number of test machines which play different roles in the assessment of the flexing resistance of soles.

The SATRA STM 465 flexing machine

One of these items of test equipment – the SATRA STM 465 whole sole flexing machine – is used to determine the resistance of materials to cut growth during repeated flexing. It is especially applicable to outsoles of protective footwear. The machine has three workstations presented horizontally for ease of loading, unloading and taking measurements. Samples are evaluated at 140 flexes per minute and the total number reached is recorded on a counter, which has the facility to pre-set the number of flexes required.

An STD 465J jig is available, which is used to locate an STD 465C chisel and support the test while the initial chisel cuts are made. All moving parts requiring access are protected by a fully interlocked safety guard, ensuring that the machine conforms to the latest safety regulations. A manual device to measure the stiffness of outsole may be required to ascertain if the outsole must be flexed in accordance with EN ISO 20344.


SATRA also provides an STM 465F version of this machine (shown at the top of this page) for testing at low temperatures, thus allowing determination of a material’s resistance to cut growth during repeated flexing to be conducted down to -20°C. As with the STM 465 machine, this ‘F’ version has three horizontally-presented workstations and operates at 140 flexes per minute. The STM 465F unit can also be fitted with a SATRA STD 465J jig to locate an STD 465C chisel.

Please see the article 'Flex testing in low temperatures' for further information on the range of SATRA test machines designed to evaluate flex resistance of components and materials at sub-zero temperatures. Visit for details of SATRA's complete range of test equipment.

How can we help?

Please email SATRA’s test equipment team ( for further information on the STM 465 and STM 465F test machines.

Publishing Data

This article was originally published on page 32 of the June 2023 issue of SATRA Bulletin.

Other articles from this issue »