What is the correct setup when using a dial gauge to measure center/edge thickness?

What is the correct setup when using a dial gauge to measure center/edge thickness?

• A. The lens is clamped in a holder and the gauge is struck at the center
• B. The lens is positioned on the gauge and the plunger lowered onto the lens
• C. The gauge reads from the outside edge
• D. The dial gauge is used to measure diameter first

Answer: (B)

Dial gauges measure a tiny vertical movement, so to get true thickness you need the lens in direct contact with the gauge. Placing the lens on the gauge and gently lowering the plunger onto the lens surface lets the reading reflect the actual thickness at the point being measured, whether at center or at the edge. Clamping the lens can deform it and skew results, striking the gauge can damage the lens and produce an unstable reading, and measuring from the outside edge would give you edge geometry rather than thickness. Reading diameter first doesn’t tell you thickness either. So the proper setup is to position the lens on the gauge and lower the plunger onto the lens.

Dial gauges measure a tiny vertical movement, so to get true thickness you need the lens in direct contact with the gauge. Placing the lens on the gauge and gently lowering the plunger onto the lens surface lets the reading reflect the actual thickness at the point being measured, whether at center or at the edge. Clamping the lens can deform it and skew results, striking the gauge can damage the lens and produce an unstable reading, and measuring from the outside edge would give you edge geometry rather than thickness. Reading diameter first doesn’t tell you thickness either. So the proper setup is to position the lens on the gauge and lower the plunger onto the lens.