Specifying Hypodermic Tubing

When considering incorporating stainless steel tubing into an application, there are several characteristics to consider: the size, the material, the temper and the method used to draw the tubing. Hypodermic tubing, or needle tubing, is primarily defined by its gauge size – the ID (inside diameter) and OD (outside diameter) – as well as the wall thickness of the tube. Component Supply stocks hypodermic tubing in two alloys, 304 and 316, and provides three basic wall thickness options: regular, thin and extra thin. While we are consistent in the dimension specifications of our tubing, we want to alert our customers of the inconsistency that often exists between different manufacturers’ specifications of wall thicknesses, some of which have up to five wall thickness options. For example, one manufacturer may label its tubing as extra thin wall but another would designate the same tubing as thin wall. This inconsistent labeling can affect customers who are trying to make the most economical choice for their applications. It is possible that one manufacturer may designate its stock of tubing as thin wall, but another more expensive company may designate it has extra thin even though it is the exact same tubing. In this case, tubing from one manufacturer may be much less expensive than the other, not because of its actual dimensions but simply because of how it is specified. Therefore, it is important for researchers and product designers to focus on specific dimensions rather than generic terms of wall thickness when making decisions to purchase hypodermic tubing.

Size charts available online provide helpful guidelines in ascertaining dimensions .Wikipedia’s Hypodermic Sizing Chart provides a convenient starting point. Component Supply also provides charts using ID and OD specifications on all hypodermic tubing product pages. A chart with inch and millimeter dimensions can be found on www.hypodermictubes.com. Once specific dimensions have been established, accurate wall thicknesses can be identified so the correct tubing is chosen for the particular application. Tolerances for the OD, ID and wall thickness must be considered carefully. Various tubing sizes allow for different tolerances, which can seriously affect certain applications. Three potentially problematic scenarios include: 1) specifying dimensions that are specific to one manufacturer rather than allowing options in supply, 2) specifying tolerances that are too close, leaving custom tubing as the only viable option and 3) specifying tolerances for OD, ID, and wall thickness with no consideration for tolerances. Any of these scenarios can pose problems for both the customer and supplier. Again, consistency does not exist between manufacturers. As research and product designers strive to choose the most efficient, effective and economical materials with which to work, specifications of the ID and OD must be prioritized rather than generic, varying labels of wall thicknesses.

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