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We are looking for specifications of the shape of an axial lead resistor. In other words what is the radius in the middle of a resistor and at the ends,...

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But why would you need such precise infos? I understand its bounding box is useful to design small pcbs, but I never felt the necessity of knowing precisley a resistor "inner" diameter. – Vladimir Cravero May 25 '14 at 17:28
It's mainly to sketch the shape of a resistor in a book, on scale :D. – Willem Van Onsem May 25 '14 at 17:30
up vote 1 down vote accepted

That depends on resistor power. Look at this:

enter image description here
Source: resistorguide.com

However those dimension may be different. Always look in the datasheet to find accurate information.

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If the information is not in the datasheet and there is no reference to a specification such as a MIL standard, it's not controlled.

If you want the information to create a 3D solid (eg .stp) model, you can just eyeball it, use calipers and radius gauge set off a sample.

enter image description here enter image description here

It's only for appearance as the manufacturer only guarantees what is in the specs and datasheet. There is no guarantee the manufacturer won't change the diameter of the ceramic tube or end-cap dimensions or lacquer viscosity so long as the datasheet dimensions are not violated (which usually means it fits within a specified cylindrical outline, and no specifics as to what happens within that envelope).

It's not uncommon to have more than one factory supplying parts with the same part number and the same manufacturer, with completely different tooling.

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