Digital Tachometer Handhled Non Contact Laser Tach Meter 2.5 to 99999 RPM Meter, Professional Replacement Tachometers with Reflection Tape Marks, Battery Included

Use this anytime idle sounds a little off.

In the off chance any homebrewers are out there looking for a tachometer to help dial in their milling speed, this is a solid choice. Put a strip on the chuck, start milling, and measure with your other hand. Works great, especially if your drill has a lock button with the wheel to adjust the speed.