A Digital Read Out (or DRO or Digital Readout) is a small computer (display unit) usually with an integrated keyboard and some mean of numeric representation. It reads the signals generated by the linear encoder (or less frequently by rotary encoders) installed to several machine's axes used to keep track of workpiece position (milling and the like) or the tool's position (lathes and grinders). In the shop argot this complete system conformed by the computer and the encoders are referred to simply as DRO. Such a system is commonly fitted to most machines in today's shops: lathes, cylindrical grinders, milling machines, surface grinders, boring mills and other machine tools to allow the operator to work faster and with greater accuracy. The use of DROs are not limited to manual equipment as CNC equipment can usually be switched to manual operation and in this case a form of DRO is emulated on the Control Panel of a robotic machine.
- Imperial (inch) and metric interchange.
- The so called "1/2" function. It takes the current value of an axis and divides it by two. It is used to find the accurate center of a workpiece or an existing feature such as a hole.
- Preset dimensions. The operator can type in the value of an axis. Used to locate a feature by using an edge finder.
- Absolute or Incremental modes. The position of a feature given on a blue print is given by one of two methods:
- Absolute, which means the coordinate is relative to the part's absolute zero (usually one of its corners or its center).
- Relative, meaning the coordinate is referred too some other feature, usually the last one machined.
- Bolt holes. The drilling or boring of several holes along an arch without using a rotary table.
- Scientific calculator. A full featured calculator has been integrated to some select models.
This is a speciality DRO system composed of a computer and an electronic scale in one small piece of equipment. Usually battery operated. Installed on the quill of a milling machine (from there its name). At this part of the machine coolant splash, flying chip and accidental shock are day-to-day events, therefore a very bad place for a glass scale used in conventional DROs. It also gives the operator a lot of comfort by being placed right in front of his eyes next to the controls that adjust the machine and it has not a single wire that can get trapped in the cluttered quill area. A very common setup is to have a regular DRO with glass scales on the milling machine's table and a separate vertical quill DRO. This gives a resolution of 0.005mm to the table position and 0.01mm to the quill. Both exceeding by far the expected "0.04mm accuracy of the milling process" (The Machinery's Handbook)