I use my gauge pins more than I thought I would
Preach!
I bought relatively inexpensive pins from 0.061- to 0.500- several years ago, and use them
constantly, often in combination with 123 blocks for all sorts of setup, measuring, and indicating tasks.
Want to bore to a fixed depth on the lathe? Lightly touch the tool to the end of work, then adjust your stop with a pin of the desired depth (or pin and 123 block) between the stop and your carriage.
Wanna position a tool EXACTLY at center height? Put a 0.500” pin in a collet in the spindle, and zero an indicator at top dead center. Now roll a 0.250” pin on top of your cutter and adjust the height until the indicator reads zero again.
Wanna check if the hole you just bored is 0.873” in diameter? Grab a 0.500” and 0.373” pin and see if you can stuff ‘em both in the hole! For some reason, using two pins like this didn’t occur to me until it was pointed out by someone else.
Gauge blocks are for the surface plate and sine bar setups. They are expensive and need to be handled carefully. I hardly ever use them.
Gauge
pins, though, are for general tasks and I use them pretty much every day I’m in the shop without any fear of damaging the surface finish. I prefer using them to mics, indicators, or anything else. Less chance to screw up.
About the only screw up I have with them is grabbing a pin from the wrong row in the box. ALWAYS check the laser engraved label in the side of the pin!
Can’t live without them now.