Pros and Cons of coarse vs fine threads ?

Hi,
I'm just about to start to build a Hemmingway rear toolpost and I will use a 12mm dimension for the clamp post instead of the 1/2 inch in the
drawings ('cos I am Mr Metric). My question is a general one about threads in this type of application :
As it happens, I have taps and dies for M12 x 1.0 (fine) and M12 x 1.75 (coarse) threads and I wondered which is perferable in a clamping application like this ? ISTM that you get the greatest clamp force with the fine thread, but then again, isn't the coarse thread a bit stronger ? What would normal engineering practice say about choosing between these 2 threads ? I actually have a slight preference for the fine thread because my die in that size is adjustable so I can make the post to fit the clamp nut whereas my die for the coarse thread is an el-cheapo non-sdjustable type which I don't have much confidence in.
All advice gratefullly received,
David
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