If you make your own marking gauges, you probably need a steel pin for the cutter. I recently discovered that I can buy good-quality marking gauge pins at Wal-Mart.
Yes, at Wal-Mart.
It might, in fact, be one of the only tools there worth buying, but you won’t find these marking gauge pins in the tools section. They’re in the sewing section.
Sewing needles are made of carbon steel, but the regular sewing needles are much too thin to use for gauge pins. However, thicker ones are available. They’re called darning needles and usually come in packs containing several sizes, most of which are 1/16″ in diameter or thicker. Those are suitable. Fabric stores sell upholstery needles, which are also the right size.
The tips need to be filed down a bit and reshaped, and the eye can be sawn off, too. It would be easy enough to get two pins out of the longer needles.
I’ve had this pin in my gauge for a little while now, and thus far I’m happy with its performance.