Fixture (tool)

A fixture is a device for securing and establishing a positive connection between a machine and a workpiece ( vice or lathe chuck ), a tool (such as chuck ), a machine tool or a sample of material ( material testing, material testing, in particular for tensile tests ).

Designs

It differs according to the type between scissors grips, wedge grips and Schraubspannköpfen.

Wedge grips without the jaw displacement during clamping, 50 kN clamping force

Various Schraubspannköpfe from which a German manufacturer program

Other types are: eccentric roller grips, thread samples and shoulder specimen grips and rope grips.

Multiple samples shoulder grips for faster serial testing

Small rope grips 200 N for testing finest strands

Compact grips for extreme temperatures in climate chambers

The clamping force is applied with mechanical grips of levers, cams, wedges or threaded spindles on the jaws. In addition, there are pneumatic and hydraulic clamping tools, which allow particularly fast clamping operations and / or very high clamping forces.

Heavy duty hydraulic chuck, clamping force 700 kN

The bending apparatus for use in tensile testing

Apparatus for measuring the peel force of adhesive tapes, to 70 ° C, max. 10 kN

Requirement

A high quality grips must not deform or damage the clamped part, but need to guarantee a compound which produce reliable and is released again. Especially when creating a force-displacement diagram would slip in the grips a faulty recording of the path and therefore unacceptable errors in the measurement result. Unsuitable fortifications of the material sample, which damage the sample, put down the breaking load and make measurements worthless.

Specialized manufacturers offer an enormous range of proven grips for use on any universal testing machines and develop more timely special devices to meet customer-specific requirements.

Numerous international and national standards relating to testing and prescribed devices for measuring, just a few examples:

  • EN ISO 75: Plastics - Determination of temperature of deflection
  • EN ISO 604: Plastics - Determination of compressive properties
  • EN ISO 6892: Metallic materials - Tensile testing (formerly EN 10002 )
  • EN ISO 13934: Textiles - Tensile properties of fabrics
  • EN ISO 14126: Fibre reinforced plastics - Determination of compressive properties in the plane of the laminate
  • EN ISO 20482: Metallic materials - Sheet and strip - Erichsen cupping test after
  • DIN 52186: Testing of wood; bending test
  • DIN 53121: Testing of paper and board - Determination of bending stiffness by the beam method
  • DIN 53292: Testing of sandwiches; Tensile test perpendicular to the faces
  • DIN 55437: Testing, cardboard, paper, cardboard
  • ISO 3303: Rubber - or plastics- coated fabrics; Determination of bursting strength
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