# Cross-Sectional Dimension of a Spring

I am trying provide Customs with a tariff code for a helical spring of steel wire. The Harmonized Tariff Schedule asks for the "cross-sectional dimension" of the spring. I have been told that this is not the same as the diameter. Does anyone know how i can find the "cross-sectional dimension" of a spring with an inside diameter of 4.7 mm and an outside diameter of 5.3 mm? Not sure you would need it, but the height is 12.4 mm. Any help would be greatly appreciated. Thank you.

• I don't have the answer, and I won't even after you add to your question, but no one will be able to help you until you say which country's or customs union's "Harmonized Tariff Schedule" is in play, here. It may even be worth digging through the actual legalese to try to find the number. There's probably a 20% chance or less that it's going to map back to any sensible engineering numbers. – TimWescott Nov 27 '19 at 20:23
• Thanks for the useful comment. Not sure why you would need to know which schedule I am referring to (US) when I clearly state what I am looking for, but it looks like someone else was able to help. – Garrett Dec 3 '19 at 15:42

The cross section of the spring wire may be what they need. If so, and we call it $$D_{wire}$$, this can be calculated as:
$$D_{wire}=\frac{(D_{out}-D_{in})}{2}=\frac{(5.3-4.7)}{2}=0.3\text{ mm}$$
• It's actually 0.3mm, surely? Need to divide by two. $D_{wire}$ would be clearer, too. – Jonathan R Swift Nov 28 '19 at 6:49