Split-nut driver

I am in the process of building a 12-inch carcase saw from a kit I purchased about three years ago.  The kit included brass bolts and split-nuts.  I could either order a driver for $30 plus shipping or come up with a method to make one myself.  The easiest method would have been to modify an existing screwdriver but I could only find one locally that had a wide enough blade, it was much too long and was more than I wanted to spend.  I didn't really have anything laying around the shop that I could use to make one either.

I did a quick search online and found one that someone had made from a spade bit that I liked.  So, back to the store for a 1/2-inch bit.  It was only $3, well within my price range for a tool that only has one use.

This one has a hex shank which will help when gluing on a handle.

I used an abrasive cut off wheel to remove the part of the bit I didn't need then used the bench grinder to reduce the width to 7/16-inch.  After grinding the end square to the sides by eye, I made a wooden v-block that I clamped to the grinder rest.  This helped hold the bit straight while I hollow ground the faces.

Once I had the thickness I wanted, I used a small triangular saw file to cut a notch in the center of the tip.  I cut the notch deep enough to allow it to guide the chainsaw file I would use to cut to final depth.  I found that the notch was still a bit too narrow to go around the saw bolt.  I moved to a slightly larger round file and widened the slot to it's finished size.

Files used to make the notch.

The tips of the blade look rounded over in this pic but are actually straight across and make full contact with the bottom of the slot in the nuts.

The faces of the the drill bit had a pretty rough grind from the factory, so I used a flap disk on my angle grinder to smooth those out and make a nice transition between the factory grind and where I had ground the faces.  I also removed just enough material that the driver would also fit the nuts on my Lie-Nielson saw which had slightly narrower slots than the nuts in my saw kit.

At some point I will probably turn a wooden handle but right now it works well enough as-is to let me finish my saw build.