Digital Position Readout (DRO) Comparison

A digital position readout (also known as a DRO, short for digital read out) provides a numerical display showing the position of your machine elements. On a milling machine a 3-axis DRO shows the X- and Y- positions of the mill table plus the Z-axis position of the cutting tool. On a lathe, a typical 2-axis DRO shows the positions of the carriage and the cross slide.

DROs help prevent common errors such as misreading the hand wheel dials or losing count of hand wheel rotations. They also provide capabilities that are impossible with mechanical hand wheels and dials, such as switching from measuring inches to measuring millimeters.

At, we carry several complete DRO packages. We have rotary encoder-based DRO packages that fit specific lathes. We have a selection of scale-based DRO packages that fit most bench top lathes and mills.

Rotary encoder-base DRO's for Lathes

These packages mount right on the cross slide, compound rest and tailstock to give you accurate depth of cut readings.

Unlike our other DRO kits, these are not a true DROs. There are two things that differentiate these from a true DRO. First, they provide readouts for the cross slide and the compound rest. They do not display the position of the carriage at all. Second, they do not actually measure the position of the cross slide or the compound rest, but measure turns of the hand wheels.

Why are these distinctions important? The first is pretty obvious, if you want to know where your lathe carriage is. This product won't help. But if you want to measure along the axis of the bed, you can set the compound rest perpendicular to the cross slide and use it to measure.

The second distinction is a finer point. Because this product measures turns of the hand wheel, there is no compensation for backlash. On a milling machine this would make this product pretty much useless. But on a lathe, you are always cutting in the same direction (on any particular cut), so backlash doesn't matter.

  • Works on any 7x10, 7x12, 7x14 or 7x16 mini lathe made by SIEG
  • Models for other and SIEG lathes
  • Resolution: 0.0001", accuracy: 0.001"
  • Buttons for On/Off, Zero, and Inch/MM
  • Zero any axis at any point
  • Inch or mm display

This product is a good value. It provides most of the features of a 'real' DRO at a very attractive price. But don't try to use it on anything but the lathe it was designed for. It simply won't work.

Rotary Encoder-Based DRO Package Comparison Table

  Digital Position Readout, 2-Axis Mini Lathe Digital Position Readout, 2-Axis 20 TPI Mini Lathe Digital Position Readout, Mini Lathe Tailstock Digital Position Readout, Bench Lathe Tailstock
Part Number 5675 5567 5879 5880
Product  Digital Position Readout, 2-Axis Mini Lathe  Digital Position Readout, 2-Axis 20 TPI Mini Lathe  Digital Position Readout, Mini Lathe Tailstock  Digital Position Readout, Bench Lathe Tailstock
Repeatability  0.00050" (0.0127 mm)  0.00050" (0.0127 mm)  0.00050" (0.0127 mm)  0.00050" (0.0127 mm)
Resolution  0.00010" (0.0025 mm)  0.00010" (0.0025 mm)  0.00010" (0.0025 mm)  0.00010" (0.0025 mm)
Accuracy  0.00100" (0.0254 mm)  0.00100" (0.0254 mm)  0.00100" (0.0254 mm)  0.00100" (0.0254 mm)
Technology  Rotary encoder  Rotary encoder  Rotary encoder  Rotary encoder
Clear to Zero  Yes  Yes  Yes  Yes
Inch/mm Display  Yes  Yes  Yes  Yes
Made In  China  China  China  China

Scale-Based DRO Packages

These DRO packages include the digital display unit, 2 or 3 scales, mounting hardware, and complete instructions for installation and use.

Except for packages that are designed for a specific machine, scale-based DRO packages are designed to mount on any machine within the range of the scales. They all come with 'universal' mounting brackets. These mounting brackets are probably all you need to mount the DRO on large machines. On smaller machines (including mini lathes and mini mills) you will probably need to make some mounting brackets. Note that the Bluetooth DRO packages, except the universal models, come with all the brackets required for the machines they support. All scale-based DRO installations require drilling and tapping a number of holes in the machine.

The biggest challenge is usually the cross slide on small lathes and the X-axis on small mills. On small lathes, the answer is sometimes to mount the DRO scale hanging in space behind the cross slide. On small mills, the smaller cross section of the Bluetooth and the DRO Pros magnetic scales can make it significantly easier to mount the X-axis scale behind the table without restricting the table travel. Glass scales are a challenge to mount on small machines because of their large cross-section and fixed lengths.

  DRO Pros Magnetic Scales
DRO Pros Magnetic Scales
Bluetooth DRO
Bluetooth DRO
3 Axis Mill 4239 5492, 5493, 5494, 5514, 5515
2 Axis Mill 4240  
2 Axis Lathe 4241 5495, 5497

Scale-Based DRO Package Comparison Table

This table includes one DRO package representing each class of DRO. The specs for the other packages in the same class are the same.
  3-Axis Universal DRO Kit for Mini Mills, Bluetooth
Part Number 5515
Product  3-Axis Universal DRO Kit for Mini Mills, Bluetooth
Repeatability  0.0002" (0.005 mm)
Resolution  0.0002" (0.005 mm)
Specified Accuracy  0.0020" (0.050 mm) / 1 m travel
Accuracy / Foot  0.0020" (0.050 mm)
Accuracy / 100 Mm  0.0020" (0.050 mm)
Scales Cut to Length by User  Yes
Scale Technology  Magnetic
Scale Protection  Coolant & dust resistant
Voltage  100-240 V
Clear to Zero  Yes
Direct Entry of Position  Yes
Inch/mm Display  Yes
Power Off Memory  No
Reversible Count Direction  Yes
Find Center  Yes
Bolt Circles  Yes
Bolt Lines  Yes
Preset Points  Yes
Tool Offsets  Yes
Radius/Diameter  Yes
Incremental/Absolute  Yes
Calculator  No
Arc Machining  No
Linear Error Compensation  No
Made In  China
Warranty  1 year
Phone Tech Support  Free

Common features of DROs include:

Repeatability How closely can you return to a previous position.
Resolution The smallest increment that can be displayed.
Accuracy The accuracy specified by the manufacturer.
Clear to Zero Press a button to set the readout to zero.
Direct Entry of Position Enter your current position.
Inch/mm Display

Displays in inches or millimeters.

Power Off Memory Maintain your coordinates and settings even if the power fails.
Reversible Count Direction Set so the dimensions increase in either direction.
Find Center Find the center of a workpiece.
Bolt Circles Lay out a bolt circle with the press of a few buttons. Move to each hole position in turn.
Bolt Lines Lay out a line of bolt holes with the press of a few buttons. Move to each hole position in turn.
Preset Points Enter or move to points and store. Select stored points and move to them.
Tool Offsets Touch off each lathe tool in your quick change tool post and record the offset. Recover the offset when you change to that tool.
Radius/Diameter Good for lathes, displays the diameter of the workpiece rather than the radius.
Incremental/Absolute This capability is good for making slots or other features where you need to work to the dimensions of the feature, while maintaining your position on the workpiece.
Calculator Use the keypad as a calculator.
Arc machining Cut a radius or an arc by moving between closely spaces points.
Linear Error Compensation Correct for scale deviations.