By Sheldon Jaffe
I recently needed a way to locate hole centers on a DRO head I’m installing on my milling machine and my eyes aren’t getting any better as I get older. IGaging doesn’t include dimensions on the data sheets for their DRO and I’m terrible at getting hole spacing correct using calipers.
Thinking the height gauge might work better than calipers, I started out using the regular angled height gauge pointer, but it was hard for me to see if the pointer tip was dead on center in the holes (Photo 1).
I then took a cheap carbide-tip scriber and cut it down to fit into the arm of my height gauge. The scriber end was turned to a 120° (included) angle and a flat was milled on one side of the scriber (Photo 2). The large flat makes it easy to see when the tip is properly centered in the holes of the DRO head. Once the scriber is centered, I can use it to scribe a line on the mounting bracket I am machining (Photo 3).
It doesn’t matter if the scriber tip is not exactly centered to the flat, all lines I scribe will be off by the same amount. Its dead reckoning – as long as I don’t change the orientation of the scriber in the height gauge, any line I scribe will be at the proper distance relative to any other line taken from the DRO holes.
This may not be very high-tech, but it’s good enough for the accuracy I needed for the DRO bracket.