Gauge systems · Tools

Calibrating tool gauges

Knitting needles and crochet hooks made according to the same gauging system and marked with the same gauge number — directly or on the packaging — can nonetheless differ to a perceptible degree in their actual diameters. This variation may be a simple result of careless sorting or otherwise insufficient quality control. However, it also has two significant nonrandom causes. One is that tools made in one country in compliance with its predominant standard, when intended for export, are marked with what is judged to be the nearest equivalent size in the standard of the destination country. Tools are also often labeled with the gauge designations of both countries.

The millimeter frequently appears either as the primary or alternate unit, rounded off to the nearest whole, half, or quarter. These increments are commonly used in countries where manufacturers work directly to a metric gauge (except for the finest-sized steel crochet hooks where the gradation is in tenths or five-hundredths of a millimeter). However, the sizes of hooks and needles produced elsewhere will not necessarily align with a scale divided exactly into quarter millimeters.

For example, I have two crochet hooks of the same highly regarded Japanese brand that are identical except for the size indications on their labels. When measured directly with slide calipers (explained below), the diameter of both hooks is 2.5 mm. One is intended for the domestic and European markets and labeled “4/0 — 2.50 mm.” The other is for export to the US, labeled “C-2 — 2.75 mm.”

Since these markings are on ergonomic handles I sacrificed the one on the latter hook, revealing the metal tool to be embossed “4/0 — 2.5.” The details of the Japanese gauge system are described in a post on the Japanese Knit and Crochet Pattern Help blog which says that a 4/0 hook can also be labeled as 2.25 mm. This means there is a ±10% tolerance in the indication of the actual size, gainsaying the widespread belief that millimeter markings are inherently more accurate than gauge numbers.

The second source of discrepancy between the nominal and actual diameters of hooks and needles is the precision with which the gauges used in their manufacture are calibrated against the underlying standard. (The term “gauge” designates both the measuring tool and the ordered system of numbers and dimensions that it incorporates.) This extends to the gauges commonly marketed to knitters and crocheters, which are typically accurate to about the same ±10% — even when marked in millimeters. (Anyone curious about slide calipers as an alternative, but less interested in background information about them, can skip directly to a how-to discussion below.)

This was a major industrial concern in mid-19th century England, when Imperial units of measurement were still in widespread international use but the push toward global metrication was gaining momentum. A leading participant in the debate, Joseph Whitworth, was among those who convincingly argued that the pivotal issue was the decimal representation of small linear measurements. In 1857, he proposed a standard wire gauge ranging from 0.001 to 0.500 inches, in increments gradually expanding from 0.001″ to 0.025″, with each represented size also serving as its gauge number. Continue reading “Calibrating tool gauges”

Crochet · History · Knitting · Tools

Gauging wooden crochet hooks and knitting needles

The first measuring tools and gauge systems documented for indicating the sizes of knitting needles and crochet hooks were developed by the wire drawing industry. This was an obvious means for labeling craft implements made from wire, but separate numbering schemes also began to appear for hooks and needles made from other materials. Larger diameters were also indicated by direct reference to ordinary measuring scales.

In a presentation of a gauge of her own devising, in 1843, Frances Lambert says:

“Knitting needles, which exceed the size of No. 1 [8 mm], can readily be measured by an inch rule.”

Swedish instructions for Tunisian crochet from 1856 state that:

“This work requires a bone crochet needle, 12 millimeters thick.”

Instructions for a foot warmer in the 23 February 1861 issue of Der Bazar, prescribe it to be:

“…knitted with two long wooden needles the size of 2 centimeters in circumference [⌀ 6.4 mm]…”

The explicit mention of circumference makes it unclear if the 1843 and 1856 texts also refer to that dimension, or if they mean diameter. Another interesting question is how precise this general form of measurement can be. Holding a needle against a ruler is a straightforward way to measure its diameter but results can easily vary from person to person. The same applies to measuring its circumference, say, by wrapping a length of thread around the needle and then measuring the length of that thread.

The optical comparison of a needle to a ruler has the advantages of simplicity and directly measuring diameter, rather than requiring its calculation (if needed) from circumference. The typical workbasket contains both a tape measure and thread, supporting either measuring technique without additional need for a gauging tool. And then there is the converse of the previous question — how accurate do such measurements need to be? Continue reading “Gauging wooden crochet hooks and knitting needles”

Crochet · History · Knitting · Tools

Frances Lambert’s knitting needle gauge

This post continues the examination of Victorian efforts at converging on a single standard for designating the sizes of knitting needles and crochet hooks, begun in the post before last. In 1842, one of the initial participants in the discussion of that topic, Frances Lambert, illustrated a gauging tool made according to a French standard based on the millimeter. In contrast, beginning in the same year, her colleagues repeatedly stated that the inch-based Standard Wire Gauge (SWG) — the source of the current UK knitting needle numbers — had been widely adopted in their field.

Lambert persisted in claiming that the SWG was only one of many systems in use and that a “Standard Filière” (wire gauge) of her own invention, tabulated below, was the way to resolve the alleged confusion. This led to a series of contentious exchanges on the subject of gauges — a term used to designate both a measuring tool and the ordered system of numbers and measurements that it incorporates. The debate is reviewed in detail in the earlier post, to which I’ve since added more information about the French system that weighed into Lambert’s work (also correcting an error in the initial version).

The evidence shows that Lambert’s alleged multiplicity of systems was not generally seen as the problem she repeatedly stated it to be. Her colleagues were comfortable indicating the sizes of knitting needles, crochet hooks, and netting meshes with the SWG, which was also employed by the manufacturers of such implements. As noted in 1848 by George Hope, the designer of one of the many alternate formats in which the SWG was produced, it “is a correct measure for the numbers used in every publication, except those of Miss Lambert.” Continue reading “Frances Lambert’s knitting needle gauge”

Crochet · Knitting · Tools

Gauging the needs of knitters and crocheters

The earliest known description of what is now called Tunisian crochet is found in Swedish instructions published on 1 January 1856 (discussed here). They prescribe “a bone crochet needle, 12 millimeters thick.” This is a surprising unit of measurement since the metric system was not adopted in Sweden until the end of 1878, with a ten year transition period before it was expected to come into widespread use.

This raises a question about other evidence of yarncraft being ahead of official metrication. The reference to the 12 mm crochet hook gainsays accepted notions of knitting needles and crochet hooks not being measured in millimeters until well into the 20th century. Other early indications of metric gauging remain to be located in Swedish sources but are found elsewhere.

The metric system originated in France, where it became legally normative in 1785. A “French gauge” for measuring the diameter of medical catheters came into widespread use during the 1830s. The gauge numbers indicate diameter in 1/3 mm increments — “1” = 1/3 mm, “2” = 2/3 mm, … “30” = 10 mm. Both the numbers and the mm sizes are marked on the one seen here, made by its inventor J.F.B. Charrière. Continue reading “Gauging the needs of knitters and crocheters”