making keystones for the window arches

There are nine arched windows in the tower on the front of our house.  Each of these arches will require eleven stones, so I have 99 stones to cut for the window arches.  Yes, that's my youngest daughter playing in the masonry sand near the front of the house.  Here's the step-by-step process of how I have been carving the stones for these windows...

The first thing I do is to score (cut a groove into) a large piece of stone with my chop saw.  Then I drive chisels into the groove until the stone splits off.  Now I have a 9" deep piece of stone.  This dimension is important.  I wish to end up with window stones that are 3.5" deep (give or take 1/2").  Further along in the process, I will split the stone in the 9" dimension to get two stones that are 4.5" deep.  Then I can face each of these stones with a chisel to achieve stones that are 3.5" deep.

Next, I score the long rectangular stone at 5" intervals.  The height of the finished stones will be 5", so this process defines the top and bottom of each finished stone.  I'm careful not to score too deeply, because I don't want saw marks showing on the bottom (visible) side of my window stones.  Looking at the giant stone from which this stone is cut, I can see fault lines, and I suspect the cut off stone will not yield as many high quality finished stones as I would have hoped for.

Driving a chisel into the grooves separates the large stone into smaller pieces of stone that will each yield two window stones.  A fault lines runs completely through one of these small stones, rendering it useless.  This stone is in the picture below the other stones.  You can see that it has split in two already.  The four stones in the top of the picture should yield a total of eight window stones.  I will lay out my cut marks so that only the split (rough) texture is showing on the bottom of the finished stone.

Now I get real busy with the chop saw.  I cut the stones in the previous step into double-thick keystones.  At this point, they have the shape of gold bars.  In this picture, you are looking at the bottom of a stone that will become two finished window stones.  To the right and left of the "keeper" piece in this picture are the tapered scrap cut-offs.  The bottom of these keystone shaped pieces is 4.5" inches wide, while the tops are 6" wide.  The bottom of this piece (facing up in this picture) is finished and requires no chiseling.

 The next step is probably the funnest and requires no noisy saw.  I take a hammer and chisel and tap the stone on all four sides in a line that circumscribes the stone at its mid point.  Eventually, the stone breaks in half, exactly on this line.  It almost always works like a dream!  The picture at the right shows the result - two stones that are almost ready to lay in the arch.  I picked this particular picture though because one of these stones has a fault.  The finished depth of these stones should be 3.5" which allows me 1" on each of the 4.5" stones to chisel a rough face that will be seen.  The stone on the left has a fault (see the iron deposits?) that impinges into, but does not traverse the stone.  I was able to use the chop saw to cut this flaw out of the stone, barely leaving enough material for me to chisel a rough face on the front of the stone.

Here are a bunch of finished stones, after I've chiseled a rough face on the fronts and in the process trimmed their depths to 3.5".  It's really hard for me to make more than eleven stones in a day.  Distractions, exhaustion, or something else always comes into play.  Oh well, I tell myself, this will last hundreds of years... so what if it takes a few weeks to cut these stones.