Although I have a Moore and Wright depth micrometre, I recently needed o check the depth of a hole that I was drilling which was much smaller than the rods on the depth mic.

I had seen a video on YouTube where a gent in the US made a simple depth gauge from a length of aluminium bar stock , a thumb screw and a length of rod.

As luck would have it I recently bought some 2mm silver steel rod for use as retaining pins for gearboxes I also had a piece of 10mm x 100mm x 14mm rough cut piece of mild steel which was left over from my lathe upgrades. The rough cut edge was actually along it’s length rather than one end (although the ends were not perfect either.

Due to the need to mill down the stock to square up the rough cut edge I thought it worth trying my hand at milling some angles along what would become the top of the gauge.

Sadly when I came to drill out the hole for the measuring rod the 1.9mm drill wandered of line and the hole although square front to back was a little off to one side. Although it was not out enough to stop it being functional it bugged me so in the end I mounted the body in a 4 jaw chuck in the lathe and used a 4mm diameter end mill to open out the hole and square it up. The end mill wasn’t quite long enough. so I had to run a drill through the last millimetre, but by then the hole was square and the problem was solved.

Finally I turned a nickel silver bush to fit the hole and them drilled that out 1.9mm and reamed it to 2mm for the measuring rod.. A turned brass thumbscrew completed the job.

The flutes on the head of the thumbscrew were machined using my Proxxon dividing head on the mill table. I made a second smaller thumb screw for the end of the measuring rod so that it didn’t poke my in the eye in use. Lastly I blackened the body of the gauge using Birchwood Casey Gun Blue