Measure radius of external arc, arc angle of measured surface should be larger than 90?
Resolution .0005″/0.01mm
Buttons: on/off, set, inch/mm, preset (+, -)
Automatic power off, move the digital unit to turn on power
Battery CR2032, Data outputMade of stainless steel
Supplied with pin gage for zero setting

Dynabrade 57289 Housing for Model 52826, 12,000 RPM
Dynabrade 57814 3-2/3" W x 7" L Dynabug Orbital Sander, Central Vacuum, .28 HP, 10,000 RPM, 3/32" Orbit 