Glossary

Terms commonly used for the manufacturing of checking fixtures and in metrology:

Adjusting: adaptation of one part into another within a mechanical assembly, such as a checking fixture. It is done according to the assembly manufacturing tolerances, and takes as a reference an axis or a hole of the assembly. The objective is making the different parts of the mechanical assembly fit perfectly, to ensure the assembly functionnality and conformity. Si our GD&T (General Dimensions and Tolerances) articles, with practical keys for the preparation of assembly plans and their manufacturing tolerances.

Anodizing: Antioxyde galvanizing treatment for aluminium parts. See our article about aluminium anodizing.

Bushing:
tube-shaped part, usually made of steel, bronze or plastic, machined in its interior and exterior surfaces to an adjusted tolerance to insert it into another part where it will have different applications. In the case of checking fixtures, bushings are inserted into dial indicator or Go/No Go gauges holders. In this case, the function of the bushing is to guide the measurement instrument, and protect the holder from the part rubbing, in order to prevent it from wear-and-tear.

CAD: Acronym for Computer-Aided Design. Software solutions for product design.

Calibration: Procedure of comparison between the value displayed by a measurement instrument and the value it should display according to a reference standard with a known value. The calibration results are then listed in a document called Calibration Certificate. The results can be displayed in two ways: 1. the correction value to apply, obtained by Reference value – Displayed value. 2. the instrument error value: Displayed value – Reference value.

CAM: Acronym for Computer-Aided Manufacturing. Software solution for the definition of manufacturing operations.
CATIA®: Acronym for Computer Aided Three-dimensional Interactive Application. PLM Solution made by Dassault Systèmes for the digital definition and simulation of products, totally integrated with DELMIA, ENOVIA, and SMARTEAM. Thanks to CATIA, the user can adapt the product manufacturing to the specific requirements of his sector and simulate all the industrial design processes, from the initial design and marketing steps to the product design, analysis, assembly and maintenance.

Checking fixture: Mechanical assembly for the dimensional verification of mass-produced parts,which function is doing the same repetitive controls on parts assemblies that have been aligned in exactly the same way, independently of the person doing the measurement. Checking fixtures are frequently used by parts and components manufacturers in industrial sectors such as automotive, household appliances, railway, aircraft, pharmaceutical, etc.
They are also called jigs or gauges and are designed for the verification of a determined part.

Depth gauge: measurement instrument consisting of a narrow ruler sliding on a lateral holding part. It is used to measure the depth of a blind hole.
Dial indicator box: Box made of solid plastic and mounted on the checking fixture to store the dial indicator.

Chemical nickel plating: anti-oxyde treatment that can be used for all metal parts.See article.

Clamp:
lever or screw-activated mechanism, which objective is fastening the parts to measure on the checking fixture. Also called spring clip.

Clipping: fastening of a part by clips, as it would be in its vehicle conditions.

Conic centring pin: pin consisting of a cylinder-shaped guiding punch and of a conic area, used to center a part by one of its holes. A centring pin can be floating – it can move in the direction of its axis, thanks to the pressure applied by a spring -, or orbiting – it can orbit on a plane cut at 90º from the centring pin axis, without the use of a spring -. If a conic centring pin is used for the centring on oblong holes, it can be rotated precisely thanks to a guiding plane set in its cylinder-shaped punch.

Foreproject: Initial design used to validate the concept of a checking fixture or of a part.

Holding points: Points to hold and fasten the parts to check. Holding points belong to a part datums. (see definition of “datum”)

Non-Quality Costs: according to Six Sigma process (see articles Putting Automotive Parts on Sort I and II, costs generated by the production of faulty material. The concept includes the costs implied in making up for the difference between the real quality and the required quality of the product/service, as well as the costs due to the loss of opportunities because of the use of ressources to correct the fault. These costs include the expenses of staff, correction and material that have been added to the production unit since the refusal of parts. They do not include detection and prevention costs.

Pin:

or threaded pin. Threaded fastening element simulating a part fixation screws on a vehicle, equipped with a handle for a better grab. (material: treated steel).

Reference bushing: hole with a template bushing, which coordinates are used for the checking fixture referencing.
Statistical Process Control (SPC): (see definition of process) definition of techniques to make the difference between stable processes, processes with an average value deviating progressively and processes with a high variability.

Technical specifications: El communication mean most commonly used between the “quality engineer” and the “draughtsman”. This document specifies all the key points of the design – materials to be used, type of commercial accessories, general tolerances, type of carved identification plates, information about the design to deliver, 2D or 3D, transport, packaging, delivery deadlines, etc.). See key points.

Transport handles: Handles, usually made of plastic, used for the checking fixture handling.

User manual: Instructions delivered by the checking fixture manufacturer about how to use it and how to position the part to be measured. It also includes, if necessary, precise indications about how to use dial indicators and set them to 0.