Quote from Wheaties
i dont understand what it means when it says the smaller the needle gauge, the larger the diameter.
i know that a 21 gauge is larger than a 25. what i dont understand is, what do they mean by diameter? is diameter the length of the needle, such as 1.5 inch for a 22 gauge? or is the diameter referring to the internal hole of the needle.
There are many different types of wire "gauge" standards, which determine the thickness (diameter) of a particular piece of wire, or needle size in the medical field. The Birmingham (aka Stub's Iron Wire) gauge is used when manufacturing hypodermic / medical needles. Each standard differs in the size of a particular gauge. As an example, a 22 gauge wire will have the following measurements:
American Wire (Brown & Sharpe) Gage 0.0253 inches
US Steel Wire Gage 0.0286 inches
British Standard (Imperial) Wire Gage 0.028 inches
Music (Piano) Wire Gage 0.049 inches
Birmingham (Stub's Iron) Wire Gage 0.028 inches
Stub's Steel Wire Gage 0.155 inches
So when you're talking about 22 gauge piano wire, it will not be the same size as a 22 gauge needle.
The production of wire as described in a previous post leads to the inverse relationship between size and gauge (small gauge - 14 = big needle, large gauge - 25 = small needle). A heated rod is pulled through a slightly smaller hole and can be repeated through smaller holes until the desired size. The first size of wire pulled through would be 1, then 2, then 3, which would correspond to the wire gauge. Therefore, the higher the number, the smaller the wire.
Confusion occurs when switching from gauge to "French" sizes. The Fr. size is based on millimeters - 1 Fr. = 1/3 mm. An 8 Fr cath would be equal to 2 and 2/3 mm (8/3 = 2 and 2/3).