Could someone explain how to properly sharpen and bend a sound post setter (the S kind) for a cello setup.
Thanks so much.
As for the "S" bends, I can't offer any advice other than to bend it until it works well (meaning that you can easily set the post upright in approximately the right position with the sharp end without the post setter fouling the f-hole, and that you can easily change the post's positioning by bumping or nudging either end of the post with the other end of the setter). On my two setters, that required making the bends tighter (closer to a right angle before and after the bend, with a radius in between, of course). But that doesn't mean that yours will need similar bends....
I personally have gotten into the general habit of stabbing the post roughly 2/3 of the way towards the top of the post (in other words: back - 2/3 of post - stab wound - 1/3 of post - top). It works for me. However, I am not a setup specialist and I would be interested in hearing where more experienced and skilled luthiers locate the stab. If they recommend somewhere else as the best stabbing location, I would recommend heeding their opinion over mine.
The reason that I mention the stab location is that it will partially determine the location and tightness of the bend on the sharp end of your setter.
As for sharpening, a narrow point will make it easier to stab the post than a fat or wide point. So, if your setter came with a wider point, try grinding down the metal to make it narrower.
And,to protect the f-hole, do cover most of the middle of the setter with heat shrink or similar, if it did not already come with protection.
Good luck with it,