One for the mathematically minded...
Anyone know a clever formula for calculating the diameter of the rim of a dome/bowl from the diameter of a flat disc - or vice versa? Specifically, if I want to make a small sphere, say 15mm across, from two hemispheres formed by doming two flat discs cut from 0.4 or 0.5mm sheet, how wide should I cut those two discs to start with? I'm sure I could do it by trial and error, but just wondered if anyone knew a way of working it out accurately to begin with.
Alan
One for the mathematically minded...
Quote:
Originally Posted by
Goldsmith
To make things simpler. The formula for working out the circumference of a sphere is Pi (3.142) x diameter, so each half sphere is half this total.
For a 15mm. diameter sphere. 15mm x 3.142 = 47.13mm (the whole sphere), divide by 2 = 23.56mm (half a sphere). So as a rough guide 2 discs 24mm. diameter will shape to a 15mm diameter sphere.
I hope this makes sense.
James
I understand what you are doing here but it does not take into account any stretching or thinning of the disc when using a doming punch, nor does it take into account the thickness of the metal.
Your formula works for a zero thickness material - but it is a good place to start to get an approximate size of the disk.
Stretching will require a smaller disk, whereas thickness will require a bigger one - how these two interact in real life depends on the type of metal, its thickness etc.
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