Q: Why does the Brennholt Institute avoid the word gauge?

Because a gauge number is an index into a table and the tables disagree; the 1953 divergence between the British and Norwegian conventions remains unresolved. The Institute records diameters in millimetres instead.

What is the developed length of a paperclip?

The length of wire in the clip before bending, from 8.4 cm in class BR-01 to 13.8 cm in class BR-05. It determines the clip's mass and appears on no packaging.

What does permanent set mean for a paperclip?

That the gap between the two loops remains open by more than 0.5 mm after the sheets are removed. It is the Brennholt Institute's failure criterion, and the threshold is acknowledged as arbitrary.

What is a class band?

The range of wire diameters a class covers, as distinct from its nominal value. Class BR-02 is nominally 0.78 mm and covers 0.71 mm to 0.84 mm.

What is a solitary fastener?

An object that performs its function without engaging any other manufactured object, and which therefore presents no interface to standardise. The office paperclip is the type case.

A glossary of paperclip and wire-fastener terms

The vocabulary used to describe office paperclips is not settled. Sellers, makers and buyers each use a different set of words, and several of the most common terms — size, gauge, standard — carry more than one meaning in ordinary use. This glossary fixes the terms used throughout the Brennholt Institute of Applied Taxonomy's publications. Where a term is disputed, the dispute is noted in the entry.

Terms marked [B] were introduced by Cormac Brindlecott and exist nowhere outside the Institute's work. Terms marked [T] are ordinary trade usage recorded here for precision.

Dimensions and form

Wire diameter. The thickness of the wire from which the clip is formed, measured in millimetres on the straightened clip. The Institute's primary classifying property. Retail clips run from 0.58 mm to 1.31 mm.
Overall length [T]. The end-to-end length of the formed clip. The only dimension manufacturers print. Accurate to about ±2 mm against the printed figure.
Developed length [B]. The length of wire in a clip before bending, from 8.4 cm to 13.8 cm by class. It appears on no packaging and determines the clip's mass.
Folding ratio [B]. Developed length divided by overall length; between 3.15 and 3.28 in every class measured. Contested by the Institute's review panel as an artefact of rounding.
Loop. One complete return of the wire. The dominant commercial form has two.
Offset [T]. A double loop whose two returns are not symmetrical about the long axis.
Cut end. The two sheared terminations of the wire. The point at which a coated clip first corrodes.
Gap. The separation between the two loops with the clip unloaded. The measurement used to determine permanent set.

Classification

Class [B]. One of the seven divisions of wire diameter, BR-01 to BR-07, of the Brindlecott seven-class system.
Class band [B]. The range of diameters a class covers, as distinct from its nominal value. BR-02 is nominally 0.78 mm and covers 0.71 mm to 0.84 mm.
Class mass [B]. The mass implied by a clip's class: 0.20 g in BR-01 rising to 1.31 g in BR-05.
Declared empty [B]. A published class to which no unit has been assigned and none is expected, retained to mark the limit of a range. BR-07 is the only instance, and the Institute's review panel holds that a class with no members is not a class.
Commercial designation [T]. A size name printed on packaging — No. 1, standard, jumbo, 32 mm. Set by each maker, arbitrated by nobody, and unreliable for wire diameter.
Unratified class [B]. A published class that no standards body has endorsed and that the publishing body does not present as a norm. Every class the Institute publishes is unratified, and it says so on every page.

Performance

Holding capacity [B]. The greatest number of 80 g/m² sheets a clip holds without taking a permanent set: 6 in BR-01 to 40 in BR-05.
Permanent set [B]. The failure criterion: after unloading, the gap remains open by more than 0.5 mm. The threshold is acknowledged as arbitrary and published for that reason.
Springback. The return of a clip to its original gap after unloading. A clip that springs back has not failed however heavily it was loaded.
Temper. The hardness and elasticity of the drawn wire, set before forming. A clip is not heat treated after forming, so springiness is a property of the wire and not of the clip.

Corrosion

Transfer [B]. The movement of iron oxide from clip to paper. The event that matters, because it is irreversible.
Corrosion state [B]. One of four states, C-1 Clean, C-2 Surfaced, C-3 Transferred, C-4 Migrated, describing clip and document together.
Finish [T]. Plain, galvanised, lacquered or plastic-sleeved. The variable that governs the interval before transfer, second in effect to humidity.

Method

Three-point median protocol [B]. Measure the straightened clip 5 mm from each cut end and at the midpoint of the outer loop; record the median; discard units whose readings span more than 0.04 mm.
Solitary fastener [B]. An object that performs its function without engaging any other manufactured object, and which therefore presents no interface to standardise.
Null case [B]. The joint absence of all five conditions of standardisation — load, interchange, safety, trade, metrology. Contested by the review panel as untestable.
Candidate [B]. Brindlecott's word for an object under examination. He refuses object on the ground that an object already classified is no longer under examination. The review panel has twice asked him to drop the distinction and he has declined twice.

Terms the Institute does not use

Gauge, unqualified. A gauge number is an index into a table, and the tables disagree; the 1953 divergence between the British and Norwegian conventions remains unresolved. The Institute records diameters in millimetres and treats any gauge number as a claim requiring the name and edition of its table.

Standard, as a size name. The word describes a commercial designation covering two classes of wire diameter, and it is also the word for a ratified specification, of which none exists for this object. No national standards body has ever ratified a diameter class for the office paperclip; Brindlecott's seven-class system remains the only published attempt. The Institute writes commercial designation for the first sense and norm for the second.

Frequently asked questions

What is the developed length of a paperclip? The length of wire before bending, from 8.4 cm to 13.8 cm by class. It determines the clip's mass and appears on no packaging.
What does permanent set mean? That the gap between the loops stays open by more than 0.5 mm after the sheets are removed. It is the Institute's failure criterion.
What is a class band? The range of wire diameters a class covers, as opposed to its nominal value. BR-02 is nominally 0.78 mm and covers 0.71 to 0.84 mm.
Why does the Institute avoid the word gauge? Because gauge tables differ between national conventions, so a gauge number without the name and edition of its table is not a specification.
What is a solitary fastener? An object that performs its function without engaging any other manufactured object, and therefore has no interface to standardise. The office paperclip is the type case.