Center gauges are gauges used in lathe work for checking the angles when grinding the profiles of single-point screw-cutting tool bits and centers.  

These gauges are most commonly used when hand-grinding threading tool bits on a bench grinder, although they may be used with tool and cutter grinders.

 Very Handy Gauge For Grinding & Setting Thread Cutting Tools.

• Permanently etched graduations.

• Edge profile ground.

• Useful to find number of threads per inch by means of graduations in  14ths, 24ths and 32nds of an inch.
Three options:
1. WhitWorth or English Standard angle 55°
2. ISO standard 60°
3. USA standard 60°