Gauge Blocks and Gauge Pins

These are Yellow Level Tools and are unlocked by Metal Shop Orientation

• The blocks are the length reference for the shop.
• The length of each block is laser-etched into the side.
  • The blocks are accurate to the specified length, within a few millionths of an inch.
• The faces of the blocks are lapped extremely flat, and very susceptible to damage.
  • Visible scratches, even if they can't be felt with a finger, can be cause for replacement.
• Blocks can be slid together in such a way that they stick to one another.
  • Make sure the blocks are clean, dry, and free of oils. Use lint-free wipes to clean them.
  • This is called “wringing”, and no one knows exactly how it works.
• Blocks can be wrung together into stacks:
  • To be used on the Surface Plate as a height reference.
  • To be used on the Surface Plate, in conjunction with a Sine Bar, to create extremely precise angular references.
  • To be used with micrometers, as a relative thickness/width measurement.

• These pins are “minus” pins, meaning they're one or two ten-thousandths of an inch smaller than the number etched on each pin.
• Gauge pins are generally used to quickly and precisely measure small hole diameters, typically when reaming or boring.
  • Typically, you would use 3 pins: The nominal size, plus one smaller and one larger pin.
  • If the smaller pin fits, but the nominal doesn't, your hole is undersize.
  • If the nominal pin fits, and the larger pin doesn't, your hole is on-size.
  • If the larger pin fits, you're oversize. Oops.
• Do not use force when trying to fit pins. They can, and will, get stuck.