I broke down and bought a lesser expensive core drill.  We are trying to decide if it is worth while buying the high end HP Lapidary drill that I don't have room for.  Unfortunately theirs is too tall to fit in my current work area (You need a crane to tip it upright and move into position.)   I would either need to set it up and then build housing around it or need to leave it exposed to the elements.

The first week was figuring out how to set it up.  We ended up filling a metal milk crate with concrete and securing it onto the top.  It turns out that this 200 pounds is not always enough weight and using the larger bits require me standing on top of the crate.  Now we are working out the best way to secure the rock while drilling.  Since this is hand driven, it has had its challenges.

The bits I purchased are intended for concrete.  They work well for soft material.  The actual drill times are 15 minutes  for 3 cuts.  Not bad!  takes 5 minutes to get the rock secured between the cuts.  We haven't begun to figure out how to get cuts 4 & 5 yet.  We did try drilling some jasper.  It ended up taking 50 minutes for the 3 cuts.  Still a significant time savings but hard on the bits.  Looking for stronger bits that will work on the machine I have.

Hand grinding takes about the same amount of time being we are only doing 3 cuts.  The real savings is the length of machine time it takes to grind to round.  A soft 3" sphere looks to take about 1.5 hours compared to 3 days.  Once the sphere is round, the machine time is the same.

Overall, it seems the the time savings is 1 to 3 weeks.  That is pretty significant.  

The disadvantage is there is a lot more waste with core drilling.  I do not get the slab yield that I do with cutting with the saw.  I am thinking if I cut the standard cube with the saw, there will still be slabs with the added advantage of seeing the pattern in the rock that I will want in the sphere.  Last but not least, it requires me to spend significant time standing at the drill during use.  

A work in progress.