Engineering snapshot · Nº 05
Pick the Right Gauge
Five instruments, from caliper to CMM, and how far to trust each one.
Digital MachineQuick-Turn CNC- 01
01 · Calibrated hand tool
Caliper
±0.001″ practical: layout and roughing checks, never final bores.
Trust it forLayout & roughing - 02
02 · Calibrated hand tool
Micrometer
0.0001″ on diameters: the shop's tenths workhorse.
Trust it forTenths on diameters - 03
03 · Reference standards
Gage blocks & pins
The reference the other instruments are checked against.
Trust it forCalibration reference - 04
04 · Coordinate measuring machine
CMM
GD&T position, profile and datums, with first-article reports.
Trust it forGD&T + first article - 05
05 · Non-contact optical systems
Optical / 3D profiler
Non-contact: soft, thin or tiny features a probe would deflect.
Trust it forNon-contact features
The gagemaker's
rule
4–10×
Rule of thumb: the gauge should be 4–10× more precise than the tolerance it checks. When a hand tool can't get there, the feature moves up the ladder, to the CMM or the optics.
In our California shop: calibrated hand tools, pin and thread gauges, height gauges on granite plates, CMMs with GD&T and first-article reports, 2D optical measurement, 3D optical surface profiling and optical comparator checks.