Variable size Canning Funnel

This Design
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There are literally dozens of designs for Mason Jar canning funnels. So what makes this one special?

* Most designs I've encountered are just a simple cone into a cylinder. I've built this with a nice radius in the throat. A nod to chickenchuck040 for the arc module (see attribution).

* Mason Jars and their lids are expensive where I live. So it's cheaper to collect commercial jars and purchase replacement lids. The sample STLs I've included are for the most commonly available jars. 67mm & 57mm throats.

* Because commercial jar have a large range of throat sizes, my design is also very easily resizable.

Using The Design
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The Canning Funnel was designed in OpenSCAD. It is a "customiser" that includes two variables used to adjust the size of the funnel to suite different commercial jar throat diameters:

`JarThroatSize = 57;`
`JarThroatDepth = 15;`

The "JarThroatSize" defines the outer diameter of the throat. The "J